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ELEMENTS
OF
CHEMISTRY,
IN A
NEW SYSTEMATIC ORDER,
CONTAINING ALL THE
MODERN DISCOVERIES.
ILLUSTRATED WITH THIRTEEN COPPERPLATES.
BY MR LAVOISIER,
Member of the Academy of Sciences, Royal Society of Medicine, and
Agricultural Society of Paris, of the Royal Society of London, and
Philosophical Societies of Orleans, Bologna, Basil, Philadelphia,
Haerlem, Manchester, &c. &c.
TRANSLATED FROM THE FRENCH,
BY ROBERT KERR, F.R. & A.SS.E.
Member of the Royal College of Surgeons, and Surgeon to the Orphan
Hospital of Edinburgh.
EDINBURGH: PRINTED FOR WILLIAM CREECH, AND SOLD IN LONDON BY G. G. AND
J. J. ROBINSONS.
MDCCXC.
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Transcriber's note: Tables needed to be split to fit space
constraints. Minor typos have been corrected and footnotes moved to the
end of the chapters. The italic markup for single italized
letters (such as variables in equations) and weight abbreviations are
deleted for easier reading.
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ADVERTISEMENT OF THE TRANSLATOR.
The very high character of Mr Lavoisier as a chemical philosopher, and
the great revolution which, in the opinion of many excellent chemists,
he has effected in the theory of chemistry, has long made it much
desired to have a connected account of his discoveries, and of the new
theory he has founded upon the modern experiments written by himself.
This is now accomplished by the publication of his Elements of
Chemistry; therefore no excuse can be at all necessary for giving the
following work to the public in an English dress; and the only
hesitation of the Translator is with regard to his own abilities for the
task. He is most ready to confess, that his knowledge of the composition
of language fit for publication is far inferior to his attachment to
the subject, and to his desire of appearing decently before the judgment
of the world.
He has earnestly endeavoured to give the meaning of the Author with the
most scrupulous fidelity, having paid infinitely greater attention to
accuracy of translation than to elegance of stile. This last indeed, had
he even, by proper labour, been capable of attaining, he has been
obliged, for very obvious reasons, to neglect, far more than accorded
with his wishes. The French copy did not reach his hands before the
middle of September; and it was judged necessary by the Publisher that
the Translation should be ready by the commencement of the University
Session at the end of October.
He at first intended to have changed all the weights and measures used
by Mr Lavoisier into their correspondent English denominations, but,
upon trial, the task was found infinitely too great for the time
allowed; and to have executed this part of the work inaccurately, must
have been both useless and misleading to the reader. All that has been
attempted in this way is adding, between brackets ( ), the degrees of
Fahrenheit's scale corresponding with those of Reaumeur's thermometer,
which is used by the Author. Rules are added, however, in the Appendix,
for converting the French weights and measures into English, by which
means the reader may at any time calculate such quantities as occur,
when desirous of comparing Mr Lavoisier's experiments with those of
British authors.
By an oversight, the first part of the translation went to press without
any distinction being preserved between charcoal and its simple
elementary part, which enters into chemical combinations, especially
with oxygen or the acidifying principle, forming carbonic acid. This
pure element, which exists in great plenty in well made charcoal, is
named by Mr Lavoisier _carbone_, and ought to have been so in the
translation; but the attentive reader can very easily rectify the
mistake. There is an error in Plate XI. which the engraver copied
strictly from the original, and which was not discovered until the plate
was worked off at press, when that part of the Elements which treats of
the apparatus there represented came to be translated. The two tubes 21.
and 24. by which the gas is conveyed into the bottles of alkaline
solution 22. 25. should have been made to dip into the liquor, while the
other tubes 23. and 26. which carry off the gas, ought to have been cut
off some way above the surface of the liquor in the bottles.
A few explanatory notes are added; and indeed, from the perspicuity of
the Author, very few were found necessary. In a very small number of
places, the liberty has been taken of throwing to the bottom of the
page, in notes, some parenthetical expressions, only relative to the
subject, which, in their original place, tended to confuse the sense.
These, and the original notes of the Author, are distinguished by the
letter A, and to the few which the Translator has ventured to add, the
letter E is subjoined.
Mr Lavoisier has added, in an Appendix, several very useful Tables for
facilitating the calculations now necessary in the advanced state of
modern chemistry, wherein the most scrupulous accuracy is required. It
is proper to give some account of these, and of the reasons for omitting
several of them.
No. I. of the French Appendix is a Table for converting ounces, gros,
and grains, into the decimal fractions of the French pound; and No. II.
for reducing these decimal fractions again into the vulgar subdivisions.
No. III. contains the number of French cubical inches and decimals which
correspond to a determinate weight of water.
The Translator would most readily have converted these Tables into
English weights and measures; but the necessary calculations must have
occupied a great deal more time than could have been spared in the
period limited for publication. They are therefore omitted, as
altogether useless, in their present state, to the British chemist.
No. IV. is a Table for converting lines or twelfth parts of the inch,
and twelfth parts of lines, into decimal fractions, chiefly for the
purpose of making the necessary corrections upon the quantities of
gasses according to their barometrical pressure. This can hardly be at
all useful or necessary, as the barometers used in Britain are graduated
in decimal fractions of the inch, but, being referred to by the Author
in the text, it has been retained, and is No. I. of the Appendix to
this Translation.
No. V. Is a Table for converting the observed heights of water within
the jars used in pneumato-chemical experiments into correspondent
heights of mercury for correcting the volume of gasses. This, in Mr
Lavoisier's Work, is expressed for the water in lines, and for the
mercury in decimals of the inch, and consequently, for the reasons given
respecting the Fourth Table, must have been of no use. The Translator
has therefore calculated a Table for this correction, in which the water
is expressed in decimals, as well as the mercury. This Table is No. II.
of the English Appendix.
No. VI. contains the number of French cubical inches and decimals
contained in the corresponding ounce-measures used in the experiments of
our celebrated countryman Dr Priestley. This Table, which forms No. III.
of the English Appendix, is retained, with the addition of a column, in
which the corresponding English cubical inches and decimals are
expressed.
No. VII. Is a Table of the weights of a cubical foot and inch, French
measure, of the different gasses expressed in French ounces, gros,
grains, and decimals. This, which forms No. VI. of the English Appendix,
has been, with considerable labour, calculated into English weight and
measure.
No. VIII. Gives the specific gravities of a great number of bodies, with
columns, containing the weights of a cubical foot and inch, French
measure, of all the substances. The specific gravities of this Table,
which is No. VII. of the English Appendix, are retained, but the
additional columns, as useless to the British philosopher, are omitted;
and to have converted these into English denominations must have
required very long and painful calculations.
Rules are subjoined, in the Appendix to this translation, for converting
all the weights and measures used by Mr Lavoisier into corresponding
English denominations; and the Translator is proud to acknowledge his
obligation to the learned Professor of Natural Philosophy in the
University of Edinburgh, who kindly supplied him with the necessary
information for this purpose. A Table is likewise added, No. IV. of the
English Appendix, for converting the degrees of Reaumeur's scale used by
Mr Lavoisier into the corresponding degrees of Fahrenheit, which is
universally employed in Britain[1].
This Translation is sent into the world with the utmost diffidence,
tempered, however, with this consolation, that, though it must fall
greatly short of the elegance, or even propriety of language, which
every writer ought to endeavour to attain, it cannot fail of advancing
the interests of true chemical science, by disseminating the accurate
mode of analysis adopted by its justly celebrated Author. Should the
public call for a second edition, every care shall be taken to correct
the forced imperfections of the present translation, and to improve the
work by valuable additional matter from other authors of reputation in
the several subjects treated of.
EDINBURGH, }
Oct. 23. 1789. }
FOOTNOTES:
[1] The Translator has since been enabled, by the kind assistance of the
gentleman above alluded to, to give Tables, of the same nature with
those of Mr Lavoisier, for facilitating the calculations of the results
of chemical experiments.
PREFACE OF THE AUTHOR.
When I began the following Work, my only object was to extend and
explain more fully the Memoir which I read at the public meeting of the
Academy of Sciences in the month of April 1787, on the necessity of
reforming and completing the Nomenclature of Chemistry. While engaged in
this employment, I perceived, better than I had ever done before, the
justice of the following maxims of the Abbe de Condillac, in his System
of Logic, and some other of his works.
"We think only through the medium of words.--Languages are true
analytical methods.--Algebra, which is adapted to its purpose in every
species of expression, in the most simple, most exact, and best manner
possible, is at the same time a language and an analytical method.--The
art of reasoning is nothing more than a language well arranged."
Thus, while I thought myself employed only in forming a Nomenclature,
and while I proposed to myself nothing more than to improve the chemical
language, my work transformed itself by degrees, without my being able
to prevent it, into a treatise upon the Elements of Chemistry.
The impossibility of separating the nomenclature of a science from the
science itself, is owing to this, that every branch of physical science
must consist of three things; the series of facts which are the objects
of the science, the ideas which represent these facts, and the words by
which these ideas are expressed. Like three impressions of the same
seal, the word ought to produce the idea, and the idea to be a picture
of the fact. And, as ideas are preserved and communicated by means of
words, it necessarily follows that we cannot improve the language of
any science without at the same time improving the science itself;
neither can we, on the other hand, improve a science, without improving
the language or nomenclature which belongs to it. However certain the
facts of any science may be, and, however just the ideas we may have
formed of these facts, we can only communicate false impressions to
others, while we want words by which these may be properly expressed.
To those who will consider it with attention, the first part of this
treatise will afford frequent proofs of the truth of the above
observations. But as, in the conduct of my work, I have been obliged to
observe an order of arrangement essentially differing from what has been
adopted in any other chemical work yet published, it is proper that I
should explain the motives which have led me to do so.
It is a maxim universally admitted in geometry, and indeed in every
branch of knowledge, that, in the progress of investigation, we should
proceed from known facts to what is unknown. In early infancy, our ideas
spring from our wants; the sensation of want excites the idea of the
object by which it is to be gratified. In this manner, from a series of
sensations, observations, and analyses, a successive train of ideas
arises, so linked together, that an attentive observer may trace back to
a certain point the order and connection of the whole sum of human
knowledge.
When we begin the study of any science, we are in a situation,
respecting that science, similar to that of children; and the course by
which we have to advance is precisely the same which Nature follows in
the formation of their ideas. In a child, the idea is merely an effect
produced by a sensation; and, in the same manner, in commencing the
study of a physical science, we ought to form no idea but what is a
necessary consequence, and immediate effect, of an experiment or
observation. Besides, he that enters upon the career of science, is in a
less advantageous situation than a child who is acquiring his first
ideas. To the child, Nature gives various means of rectifying any
mistakes he may commit respecting the salutary or hurtful qualities of
the objects which surround him. On every occasion his judgments are
corrected by experience; want and pain are the necessary consequences
arising from false judgment; gratification and pleasure are produced by
judging aright. Under such masters, we cannot fail to become well
informed; and we soon learn to reason justly, when want and pain are the
necessary consequences of a contrary conduct.
In the study and practice of the sciences it is quite different; the
false judgments we form neither affect our existence nor our welfare;
and we are not forced by any physical necessity to correct them.
Imagination, on the contrary, which is ever wandering beyond the bounds
of truth, joined to self-love and that self-confidence we are so apt to
indulge, prompt us to draw conclusions which are not immediately derived
from facts; so that we become in some measure interested in deceiving
ourselves. Hence it is by no means to be wondered, that, in the science
of physics in general, men have often made suppositions, instead of
forming conclusions. These suppositions, handed down from one age to
another, acquire additional weight from the authorities by which they
are supported, till at last they are received, even by men of genius, as
fundamental truths.
The only method of preventing such errors from taking place, and of
correcting them when formed, is to restrain and simplify our reasoning
as much as possible. This depends entirely upon ourselves, and the
neglect of it is the only source of our mistakes. We must trust to
nothing but facts: These are presented to us by Nature, and cannot
deceive. We ought, in every instance, to submit our reasoning to the
test of experiment, and never to search for truth but by the natural
road of experiment and observation. Thus mathematicians obtain the
solution of a problem by the mere arrangement of data, and by reducing
their reasoning to such simple steps, to conclusions so very obvious, as
never to lose sight of the evidence which guides them.
Thoroughly convinced of these truths, I have imposed upon myself, as a
law, never to advance but from what is known to what is unknown; never
to form any conclusion which is not an immediate consequence necessarily
flowing from observation and experiment; and always to arrange the
facts, and the conclusions which are drawn from them, in such an order
as shall render it most easy for beginners in the study of chemistry
thoroughly to understand them. Hence I have been obliged to depart from
the usual order of courses of lectures and of treatises upon chemistry,
which always assume the first principles of the science, as known, when
the pupil or the reader should never be supposed to know them till they
have been explained in subsequent lessons. In almost every instance,
these begin by treating of the elements of matter, and by explaining the
table of affinities, without considering, that, in so doing, they must
bring the principal phenomena of chemistry into view at the very outset:
They make use of terms which have not been defined, and suppose the
science to be understood by the very persons they are only beginning to
teach. It ought likewise to be considered, that very little of chemistry
can be learned in a first course, which is hardly sufficient to make the
language of the science familiar to the ears, or the apparatus familiar
to the eyes. It is almost impossible to become a chemist in less than
three or four years of constant application.
These inconveniencies are occasioned not so much by the nature of the
subject, as by the method of teaching it; and, to avoid them, I was
chiefly induced to adopt a new arrangement of chemistry, which appeared
to me more consonant to the order of Nature. I acknowledge, however,
that in thus endeavouring to avoid difficulties of one kind, I have
found myself involved in others of a different species, some of which I
have not been able to remove; but I am persuaded, that such as remain do
not arise from the nature of the order I have adopted, but are rather
consequences of the imperfection under which chemistry still labours.
This science still has many chasms, which interrupt the series of facts,
and often render it extremely difficult to reconcile them with each
other: It has not, like the elements of geometry, the advantage of being
a complete science, the parts of which are all closely connected
together: Its actual progress, however, is so rapid, and the facts,
under the modern doctrine, have assumed so happy an arrangement, that we
have ground to hope, even in our own times, to see it approach near to
the highest state of perfection of which it is susceptible.
The rigorous law from which I have never deviated, of forming no
conclusions which are not fully warranted by experiment, and of never
supplying the absence of facts, has prevented me from comprehending in
this work the branch of chemistry which treats of affinities, although
it is perhaps the best calculated of any part of chemistry for being
reduced into a completely systematic body. Messrs Geoffroy, Gellert,
Bergman, Scheele, De Morveau, Kirwan, and many others, have collected a
number of particular facts upon this subject, which only wait for a
proper arrangement; but the principal data are still wanting, or, at
least, those we have are either not sufficiently defined, or not
sufficiently proved, to become the foundation upon which to build so
very important a branch of chemistry. This science of affinities, or
elective attractions, holds the same place with regard to the other
branches of chemistry, as the higher or transcendental geometry does
with respect to the simpler and elementary part; and I thought it
improper to involve those simple and plain elements, which I flatter
myself the greatest part of my readers will easily understand, in the
obscurities and difficulties which still attend that other very useful
and necessary branch of chemical science.
Perhaps a sentiment of self-love may, without my perceiving it, have
given additional force to these reflections. Mr de Morveau is at
present engaged in publishing the article _Affinity_ in the Methodical
Encyclopaedia; and I had more reasons than one to decline entering upon a
work in which he is employed.
It will, no doubt, be a matter of surprise, that in a treatise upon the
elements of chemistry, there should be no chapter on the constituent and
elementary parts of matter; but I shall take occasion, in this place, to
remark, that the fondness for reducing all the bodies in nature to three
or four elements, proceeds from a prejudice which has descended to us
from the Greek Philosophers. The notion of four elements, which, by the
variety of their proportions, compose all the known substances in
nature, is a mere hypothesis, assumed long before the first principles
of experimental philosophy or of chemistry had any existence. In those
days, without possessing facts, they framed systems; while we, who have
collected facts, seem determined to reject them, when they do not agree
with our prejudices. The authority of these fathers of human philosophy
still carry great weight, and there is reason to fear that it will even
bear hard upon generations yet to come.
It is very remarkable, that, notwithstanding of the number of
philosophical chemists who have supported the doctrine of the four
elements, there is not one who has not been led by the evidence of facts
to admit a greater number of elements into their theory. The first
chemists that wrote after the revival of letters, considered sulphur and
salt as elementary substances entering into the composition of a great
number of substances; hence, instead of four, they admitted the
existence of six elements. Beccher assumes the existence of three kinds
of earth, from the combination of which, in different proportions, he
supposed all the varieties of metallic substances to be produced. Stahl
gave a new modification to this system; and succeeding chemists have
taken the liberty to make or to imagine changes and additions of a
similar nature. All these chemists were carried along by the influence
of the genius of the age in which they lived, which contented itself
with assertions without proofs; or, at least, often admitted as proofs
the slighted degrees of probability, unsupported by that strictly
rigorous analysis required by modern philosophy.
All that can be said upon the number and nature of elements is, in my
opinion, confined to discussions entirely of a metaphysical nature. The
subject only furnishes us with indefinite problems, which may be solved
in a thousand different ways, not one of which, in all probability, is
consistent with nature. I shall therefore only add upon this subject,
that if, by the term _elements_, we mean to express those simple and
indivisible atoms of which matter is composed, it is extremely probable
we know nothing at all about them; but, if we apply the term _elements_,
or _principles of bodies_, to express our idea of the last point which
analysis is capable of reaching, we must admit, as elements, all the
substances into which we are capable, by any means, to reduce bodies by
decomposition. Not that we are entitled to affirm, that these substances
we consider as simple may not be compounded of two, or even of a greater
number of principles; but, since these principles cannot be separated,
or rather since we have not hitherto discovered the means of separating
them, they act with regard to us as simple substances, and we ought
never to suppose them compounded until experiment and observation has
proved them to be so.
The foregoing reflections upon the progress of chemical ideas naturally
apply to the words by which these ideas are to be expressed. Guided by
the work which, in the year 1787, Messrs de Morveau, Berthollet, de
Fourcroy, and I composed upon the Nomenclature of Chemistry, I have
endeavoured, as much as possible, to denominate simple bodies by simple
terms, and I was naturally led to name these first. It will be
recollected, that we were obliged to retain that name of any substance
by which it had been long known in the world, and that in two cases only
we took the liberty of making alterations; first, in the case of those
which were but newly discovered, and had not yet obtained names, or at
least which had been known but for a short time, and the names of which
had not yet received the sanction of the public; and, secondly, when the
names which had been adopted, whether by the ancients or the moderns,
appeared to us to express evidently false ideas, when they confounded
the substances, to which they were applied, with others possessed of
different, or perhaps opposite qualities. We made no scruple, in this
case, of substituting other names in their room, and the greatest number
of these were borrowed from the Greek language. We endeavoured to frame
them in such a manner as to express the most general and the most
characteristic quality of the substances; and this was attended with the
additional advantage both of assisting the memory of beginners, who find
it difficult to remember a new word which has no meaning, and of
accustoming them early to admit no word without connecting with it some
determinate idea.
To those bodies which are formed by the union of several simple
substances we gave new names, compounded in such a manner as the nature
of the substances directed; but, as the number of double combinations is
already very considerable, the only method by which we could avoid
confusion, was to divide them into classes. In the natural order of
ideas, the name of the class or genus is that which expresses a quality
common to a great number of individuals: The name of the species, on the
contrary, expresses a quality peculiar to certain individuals only.
These distinctions are not, as some may imagine, merely metaphysical,
but are established by Nature. "A child," says the Abbe de Condillac,
"is taught to give the name _tree_ to the first one which is pointed out
to him. The next one he sees presents the same idea, and he gives it the
same name. This he does likewise to a third and a fourth, till at last
the word _tree_, which he first applied to an individual, comes to be
employed by him as the name of a class or a genus, an abstract idea,
which comprehends all trees in general. But, when he learns that all
trees serve not the same purpose, that they do not all produce the same
kind of fruit, he will soon learn to distinguish them by specific and
particular names." This is the logic of all the sciences, and is
naturally applied to chemistry.
The acids, for example, are compounded of two substances, of the order
of those which we consider as simple; the one constitutes acidity, and
is common to all acids, and, from this substance, the name of the class
or the genus ought to be taken; the other is peculiar to each acid, and
distinguishes it from the rest, and from this substance is to be taken
the name of the species. But, in the greatest number of acids, the two
constituent elements, the acidifying principle, and that which it
acidifies, may exist in different proportions, constituting all the
possible points of equilibrium or of saturation. This is the case in the
sulphuric and the sulphurous acids; and these two states of the same
acid we have marked by varying the termination of the specific name.
Metallic substances which have been exposed to the joint action of the
air and of fire, lose their metallic lustre, increase in weight, and
assume an earthy appearance. In this state, like the acids, they are
compounded of a principle which is common to all, and one which is
peculiar to each. In the same way, therefore, we have thought proper to
class them under a generic name, derived from the common principle; for
which purpose, we adopted the term _oxyd_; and we distinguish them from
each other by the particular name of the metal to which each belongs.
Combustible substances, which in acids and metallic oxyds are a specific
and particular principle, are capable of becoming, in their turn, common
principles of a great number of substances. The sulphurous combinations
have been long the only known ones in this kind. Now, however, we know,
from the experiments of Messrs Vandermonde, Monge, and Berthollet, that
charcoal may be combined with iron, and perhaps with several other
metals; and that, from this combination, according to the proportions,
may be produced steel, plumbago, &c. We know likewise, from the
experiments of M. Pelletier, that phosphorus may be combined with a
great number of metallic substances. These different combinations we
have classed under generic names taken from the common substance, with a
termination which marks this analogy, specifying them by another name
taken from that substance which is proper to each.
The nomenclature of bodies compounded of three simple substances was
attended with still greater difficulty, not only on account of their
number, but, particularly, because we cannot express the nature of their
constituent principles without employing more compound names. In the
bodies which form this class, such as the neutral salts, for instance,
we had to consider, 1st, The acidifying principle, which is common to
them all; 2d, The acidifiable principle which constitutes their peculiar
acid; 3d, The saline, earthy, or metallic basis, which determines the
particular species of salt. Here we derived the name of each class of
salts from the name of the acidifiable principle common to all the
individuals of that class; and distinguished each species by the name of
the saline, earthy, or metallic basis, which is peculiar to it.
A salt, though compounded of the same three principles, may,
nevertheless, by the mere difference of their proportion, be in three
different states. The nomenclature we have adopted would have been
defective, had it not expressed these different states; and this we
attained chiefly by changes of termination uniformly applied to the same
state of the different salts.
In short, we have advanced so far, that from the name alone may be
instantly found what the combustible substance is which enters into any
combination; whether that combustible substance be combined with the
acidifying principle, and in what proportion; what is the state of the
acid; with what basis it is united; whether the saturation be exact, or
whether the acid or the basis be in excess.
It may be easily supposed that it was not possible to attain all these
different objects without departing, in some instances, from established
custom, and adopting terms which at first sight will appear uncouth and
barbarous. But we considered that the ear is soon habituated to new
words, especially when they are connected with a general and rational
system. The names, besides, which were formerly employed, such as
_powder of algaroth_, _salt of alembroth_, _pompholix_, _phagadenic
water_, _turbith mineral_, _colcathar_, and many others, were neither
less barbarous nor less uncommon. It required a great deal of practice,
and no small degree of memory, to recollect the substances to which they
were applied, much more to recollect the genus of combination to which
they belonged. The names of _oil of tartar per deliquium_, _oil of
vitriol_, _butter of arsenic and of antimony_, _flowers of zinc_, &c.
were still more improper, because they suggested false ideas: For, in
the whole mineral kingdom, and particularly in the metallic class, there
exists no such thing as butters, oils, or flowers; and, in short, the
substances to which they give these fallacious names, are nothing less
than rank poisons.
When we published our essay on the nomenclature of chemistry, we were
reproached for having changed the language which was spoken by our
masters, which they distinguished by their authority, and handed down to
us. But those who reproach us on this account, have forgotten that it
was Bergman and Macquer themselves who urged us to make this
reformation. In a letter which the learned Professor of Upsal, M.
Bergman, wrote, a short time before he died, to M. de Morveau, he bids
him _spare no improper names; those who are learned, will always be
learned, and those who are ignorant will thus learn sooner_.
There is an objection to the work which I am going to present to the
public, which is perhaps better founded, that I have given no account of
the opinion of those who have gone before me; that I have stated only my
own opinion, without examining that of others. By this I have been
prevented from doing that justice to my associates, and more especially
to foreign chemists, which I wished to render them. But I beseech the
reader to consider, that, if I had filled an elementary work with a
multitude of quotations; if I had allowed myself to enter into long
dissertations on the history of the science, and the works of those who
have studied it, I must have lost sight of the true object I had in
view, and produced a work, the reading of which must have been extremely
tiresome to beginners. It is not to the history of the science, or of
the human mind, that we are to attend in an elementary treatise: Our
only aim ought to be ease and perspicuity, and with the utmost care to
keep every thing out of view which might draw aside the attention of the
student; it is a road which we should be continually rendering more
smooth, and from which we should endeavour to remove every obstacle
which can occasion delay. The sciences, from their own nature, present a
sufficient number of difficulties, though we add not those which are
foreign to them. But, besides this, chemists will easily perceive, that,
in the first part of my work, I make very little use of any experiments
but those which were made by myself: If at any time I have adopted,
without acknowledgment, the experiments or the opinions of M.
Berthollet, M. Fourcroy, M. de la Place, M. Monge, or, in general, of
any of those whose principles are the same with my own, it is owing to
this circumstance, that frequent intercourse, and the habit of
communicating our ideas, our observations, and our way of thinking to
each other, has established between us a sort of community of opinions,
in which it is often difficult for every one to know his own.
The remarks I have made on the order which I thought myself obliged to
follow in the arrangement of proofs and ideas, are to be applied only to
the first part of this work. It is the only one which contains the
general sum of the doctrine I have adopted, and to which I wished to
give a form completely elementary.
The second part is composed chiefly of tables of the nomenclature of the
neutral salts. To these I have only added general explanations, the
object of which was to point out the most simple processes for obtaining
the different kinds of known acids. This part contains nothing which I
can call my own, and presents only a very short abridgment of the
results of these processes, extracted from the works of different
authors.
In the third part, I have given a description, in detail, of all the
operations connected with modern chemistry. I have long thought that a
work of this kind was much wanted, and I am convinced it will not be
without use. The method of performing experiments, and particularly
those of modern chemistry, is not so generally known as it ought to be;
and had I, in the different memoirs which I have presented to the
Academy, been more particular in the detail of the manipulations of my
experiments, it is probable I should have made myself better understood,
and the science might have made a more rapid progress. The order of the
different matters contained in this third part appeared to me to be
almost arbitrary; and the only one I have observed was to class
together, in each of the chapters of which it is composed, those
operations which are most connected with one another. I need hardly
mention that this part could not be borrowed from any other work, and
that, in the principal articles it contains, I could not derive
assistance from any thing but the experiments which I have made myself.
I shall conclude this preface by transcribing, literally, some
observations of the Abbe de Condillac, which I think describe, with a
good deal of truth, the state of chemistry at a period not far distant
from our own. These observations were made on a different subject; but
they will not, on this account, have less force, if the application of
them be thought just.
'Instead of applying observation to the things we wished to know, we
have chosen rather to imagine them. Advancing from one ill founded
supposition to another, we have at last bewildered ourselves amidst a
multitude of errors. These errors becoming prejudices, are, of course,
adopted as principles, and we thus bewilder ourselves more and more. The
method, too, by which we conduct our reasonings is as absurd; we abuse
words which we do not understand, and call this the art of reasoning.
When matters have been brought this length, when errors have been thus
accumulated, there is but one remedy by which order can be restored to
the faculty of thinking; this is, to forget all that we have learned, to
trace back our ideas to their source, to follow the train in which they
rise, and, as my Lord Bacon says, to frame the human understanding anew.
'This remedy becomes the more difficult in proportion as we think
ourselves more learned. Might it not be thought that works which
treated of the sciences with the utmost perspicuity, with great
precision and order, must be understood by every body? The fact is,
those who have never studied any thing will understand them better than
those who have studied a great deal, and especially than those who have
written a great deal.'
At the end of the fifth chapter, the Abbe de Condillac adds: 'But, after
all, the sciences have made progress, because philosophers have applied
themselves with more attention to observe, and have communicated to
their language that precision and accuracy which they have employed in
their observations: In correcting their language they reason better.'
CONTENTS.
PART FIRST.
Of the Formation and Decomposition of
Aeriform Fluids,--of the Combustion
of Simple Bodies, and the Formation
of Acids, Page 1
CHAP. I.--Of the Combinations of Caloric, and
the Formation of Elastic Aeriform Fluids or
Gasses, ibid.
CHAP. II.--General Views relative to the Formation
and Composition of our Atmosphere, 26
CHAP. III.--Analysis of Atmospheric Air, and its
Division into two Elastic Fluids; one fit for
Respiration, the other incapable of being respired, 32
CHAP. IV.--Nomenclature of the several constituent
Parts of Atmospheric Air, 48
CHAP. V.--Of the Decomposition of Oxygen
Gas by Sulphur, Phosphorus, and Charcoal, and
of the Formation of Acids in general, 54
CHAP. VI.--Of the Nomenclature of Acids in general,
and particularly of those drawn from
Nitre and Sea Salt, 66
CHAP. VII.--Of the Decomposition of Oxygen
Gas by means of Metals, and the Formation of
Metallic Oxyds, 78
CHAP. VIII.--Of the Radical Principle of Water,
and of its Decomposition by Charcoal and
Iron, 83
CHAP. IX.--Of the Quantities of Caloric disengaged
from different Species of Combustion, 97
Combustion of Phosphorus, 100
SECT. I.--Combustion of Charcoal, 101
SECT. II.--Combustion of Hydrogen Gas, 102
SECT. III.--Formation of Nitric Acid, 102
SECT. IV.--Combustion of Wax, 105
SECT. V.--Combustion of Olive Oil, 106
CHAP. X.--Of the Combustion of Combustible
Substances with each other, 109
CHAP. XI.--Observations upon Oxyds and Acids
with several Bases, and upon the Composition
of Animal and Vegetable Substances, 115
CHAP. XII.--Of the Decomposition of Vegetable
and Animal Substances by the Action of Fire, 123
CHAP. XIII.--Of the Decomposition of Vegetable
Oxyds by the Vinous Fermentation, 129
CHAP. XIV.--Of the Putrefactive Fermentation, 141
CHAP. XV.--Of the Acetous Fermentation, 146
CHAP. XVI.--Of the Formation of Neutral Salts,
and of their Bases, 149
SECT. I.--Of Potash, 151
SECT. II.--Of Soda, 155
SECT. III.--Of Ammoniac, 156
SECT. IV.--Of Lime, Magnesia, Barytes, and Argill, 157
SECT. V.--Of Metallic Bodies, 159
CHAP. XVII.--Continuation of the Observations
upon Salifiable Bases, and the Formation
of Neutral Salts, 161
PART II.
Of the Combinations of Acids with Salifiable
Bases, and of the Formation
of Neutral Salts, 175
INTRODUCTION, ibid.
TABLE of Simple Substances, 175
SECT. I.--Observations upon simple Substances, 176
TABLE of Compound Oxydable and Acidifiable
Bases, 179
SECT. II.--Observations upon Compound Radicals, 180
SECT. III.--Observations upon the Combinations
of Light and Caloric with different Substances, 182
TABLE of the Combinations of Oxygen with the
Simple Substances, to face 185
SECT. IV.--Observations upon these Combinations, 185
TABLE of the Combinations of Oxygen with Compound
Radicals, 190
SECT. V.--Observations upon these Combinations, 191
TABLE of the Combinations of Azote with the
Simple Substances, 194
SECT VI.--Observations upon these Combinations
of Azote, 195
TABLE of the Combinations of Hydrogen with
Simple Substances, 198
SECT. VII.--Observations upon Hydrogen, and its
Combinations, 199
TABLE of the Binary Combinations of Sulphur
with the Simple Substances, 202
SECT. VIII.--Observations upon Sulphur, and its
Combinations, 203
TABLE of the Combinations of Phosphorus with
Simple Substances, 204
SECT. IX.--Observations upon Phosphorus and its
Combinations, 205
TABLE of the Binary Combinations of Charcoal, 207
SECT. X.--Observations upon Charcoal, and its
Combinations, 208
SECT. XI.--Observations upon the Muriatic, Fluoric,
and Boracic Radicals, and their Combinations, 209
SECT. XII.--Observations upon the Combinations
of Metals with each other, 219
TABLE of the Combinations of Azote, in the State
of Nitrous Acid, with the Salifiable Bases, 212
TABLE of the Combinations of Azote, in the State
of Nitric Acid, with the Salifiable Bases, 213
SECT. XIII.--Observations upon Nitrous and Nitric
Acids, and their Combinations with Salifiable
Bases, 214
TABLE of the Combinations of Sulphuric Acid
with the Salifiable Bases, 218
SECT. XIV.--Observations upon Sulphuric Acid,
and its Combinations, 219
TABLE of the Combinations of Sulphurous Acid, 222
SECT. XV.--Observations upon Sulphurous Acid,
and its Combinations with Salifiable Bases, 223
TABLE of the Combinations of Phosphorous and
Phosphoric Acids, 225
SECT. XVI.--Observations upon Phosphorous and
Phosphoric Acids, and their Combinations
with Salifiable Bases, 226
TABLE of the Combinations of Carbonic Acid, 228
SECT. XVII.--Observations upon Carbonic Acid,
and its Combinations with Salifiable Bases, 229
TABLE of the Combinations of Muriatic Acid, 231
TABLE of the Combinations of Oxygenated Muriatic
Acid, 232
SECT. XVIII.--Observations upon Muriatic and
Oxygenated Muriatic Acid, and their Combinations
with Salifiable Bases, 233
TABLE of the Combinations of Nitro-Muriatic Acid, 236
SECT. XIX.--Observations upon Nitro-muriatic
Acid, and its Combinations with Salifiable
Bases, 237
TABLE of the Combinations of Fluoric Acid, 239
SECT. XX.--Observations upon Fluoric Acid, and
its Combinations with Salifiable Bases, 240
TABLE of the Combinations of Boracic Acid, 242
SECT. XXI.--Observations upon Boracic Acid,
and its Combinations with Salifiable Bases, 243
TABLE of the Combinations of Arseniac Acid, 246
SECT. XXII.--Observations upon Arseniac Acid,
and its Combinations with Salifiable Bases, 247
SECT. XXIII.--Observations upon Molibdic Acid,
and its Combinations with Salifiable Bases, 249
SECT. XXIV.--Observations upon Tungstic Acid,
and its Combinations with Salifiable Bases, and
a Table of these in the order of their Affinity, 251
TABLE of the Combinations of Tartarous Acid, 253
SECT. XXV.--Observations upon Tartarous Acid,
and its Combinations with Salifiable Bases, 254
SECT. XXVI.--Observations upon Mallic Acid,
and its Combinations with Salifiable Bases, 256
TABLE of the Combinations of Citric Acid, 258
SECT. XXVII.--Observations upon Citric Acid,
and its Combinations with Salifiable Bases, 259
TABLE of the Combinations of Pyro-lignous Acid, 260
SECT. XXVIII.--Observations upon Pyro-lignous
Acid, and its Combinations with Salifiable Bases, 261
SECT. XXIX.--Observations upon Pyro-tartarous
Acid, and its Combinations with Salifiable
Bases, ibid.
TABLE of the Combinations of Pyro-mucous Acid, 263
SECT. XXX.--Observations upon Pyro-mucous
Acid, and its Combinations with Salifiable Bases, 264
TABLE of the Combinations of Oxalic Acid, 265
SECT. XXXI.--Observations upon Oxalic Acid,
and its Combinations with Salifiable Bases, 266
TABLE of the Combinations of Acetous Acid, to
face 267
SECT. XXXII.--Observations upon Acetous Acid,
and its Combinations with the Salifiable Bases, 267
TABLE of the Combinations of Acetic Acid, 271
SECT. XXXIII.--Observations upon Acetic Acid,
and its Combinations with Salifiable Bases, 272
TABLE of the Combinations of Succinic Acid, 273
SECT. XXXIV.--Observations upon Succinic Acid,
and its Combinations with Salifiable Bases, 274
SECT. XXXV.--Observations upon Benzoic Acid,
and its Combinations with Salifiable Bases, 275
SECT. XXXVI.--Observations upon Camphoric
Acid, and its Combinations with Salifiable
Bases, 276
SECT. XXXVII.--Observations upon Gallic Acid,
and its Combinations with Salifiable Bases, 277
SECT. XXXVIII.--Observations upon Lactic Acid,
and its Combinations with Salifiable Bases, 278
TABLE of the Combinations of Saccholactic Acid, 280
SECT. XXXIX.--Observations upon Saccholactic
Acid, and its Combination with Salifiable Bases, 281
TABLE of the Combinations of Formic Acid, 282
SECT. XL.--Observations upon Formic Acid, and
its Combinations with the Salifiable Bases, 283
SECT. XLI.--Observations upon the Bombic Acid,
and its Combinations with the Salifiable Bases, 284
TABLE of the Combinations of the Sebacic Acid, 285
SECT. XLII.--Observations upon the Sebacic Acid,
and its Combinations with the Salifiable Bases, 286
SECT. XLIII.--Observations upon the Lithic Acid,
and its Combinations with the Salifiable Bases, 287
TABLE of the Combinations of the Prussic Acid, 288
SECT. XLIV.--Observations upon the Prussic Acid,
and its Combinations with the Salifiable Bases, 289
PART III.
Description of the Instruments and Operations
of Chemistry, 291
INTRODUCTION, 291
CHAP. I.--Of the Instruments necessary for determining
the Absolute and Specific Gravities of
Solid and Liquid Bodies, 295
CHAP. II.--Of Gazometry, or the Measurement
of the Weight and Volume of Aeriform Substances, 304
SECT. I.--Of the Pneumato-chemical Apparatus, ibid.
SECT. II.--Of the Gazometer, 308
SECT. III.--Some other methods for Measuring
the Volume of Gasses, 319
SECT. IV.--Of the method of Separating the different
Gasses from each other, 323
SECT. V.--Of the necessary Corrections of the Volume
of Gasses, according to the Pressure of
the Atmosphere, 328
SECT. VI.--Of the Correction relative to the Degrees
of the Thermometer, 335
SECT. VII.--Example for Calculating the Corrections
relative to the Variations of Pressure and
Temperature, 337
SECT. VIII.--Method of determining the Weight
of the different Gasses, 340
CHAP. III.--Description of the Calorimeter, or
Apparatus for measuring Caloric, 343
CHAP. IV.--Of the Mechanical Operations for
Division of Bodies, 357
SECT. I.--Of Trituration, Levigation, and Pulverization, ibid.
SECT. II.--Of Sifting and Washing Powdered
Substances, 361
SECT. III.--Of Filtration, 363
SECT. IV.--Of Decantation, 365
CHAP. V.--Of Chemical means for Separating the
Particles of Bodies from each other without
Decomposition, and for Uniting them again, 367
SECT. I.--Of the Solution of Salts, 368
SECT. II.--Of Lixiviation, 373
SECT. III.--Of Evaporation, 375
SECT. IV.--Of Cristallization, 379
SECT. V.--Of Simple Distillation, 384
SECT. VI.--Of Sublimation, 388
CHAP. VI.--Of Pneumato-chemical Distillations,
Metallic Dissolutions, and some other operations
which require very complicated instruments, 390
SECT. I.--Of Compound and Pneumato-chemical
Distillations, ibid.
SECT. II.--Of Metallic Dissolutions, 398
SECT. III.--Apparatus necessary in Experiments
upon Vinous and Putrefactive Fermentations, 401
SECT. IV.--Apparatus for the Decomposition of
Water, 404
CHAP. VII.--Of the Composition and Use of
Lutes, 407
CHAP. VIII.--Of Operations upon Combustion
and Deflagration, 414
SECT. I.--Of Combustion in general, ibid.
SECT. II.--Of the Combustion of Phosphorus, 418
SECT. III.--Of the Combustion of Charcoal, 422
SECT. IV.--Of the Combustion of Oils, 426
SECT. V.--Of the Combustion of Alkohol, 433
SECT. VI.--Of the Combustion of Ether, 435
SECT. VII.--Of the Combustion of Hydrogen
Gas, and the Formation of Water, 437
SECT. VIII.--Of the Oxydation of Metals, 441
CHAP. IX.--Of Deflagration, 452
CHAP. X.--Of the Instruments necessary for Operating
upon Bodies in very high Temperatures, 460
SECT. I.--Of Fusion, ibid.
SECT. II.--Of Furnaces, 462
SECT. III.--Of increasing the Action of Fire, by
using Oxygen Gas instead of Atmospheric Air, 474
APPENDIX.
No. I.--TABLE for Converting Lines, or Twelfth
Parts of an Inch, and Fractions of Lines, into
Decimal Fractions of the Inch, 481
No. II.--TABLE for Converting the Observed
Heighth of Water in the Jars of the Pneumato-Chemical
Apparatus, expressed in Inches and
Decimals, into Corresponding Heighths of Mercury, 482
No. III.--TABLE for Converting the Ounce
Measures used by Dr Priestley into French and
English Cubical Inches, 483
No. IV.--TABLE for Reducing the Degrees of
Reaumeur's Thermometer into its corresponding
Degrees of Fahrenheit's Scale, 484
No. V.--ADDITIONAL.--RULES for Converting
French Weights and Measures into correspondent
English Denominations, 485
No. VI.--TABLE of the Weights of the different
Gasses, at 28 French inches, or 29.84 English
inches barometrical pressure, and at 10 deg. (54.5 deg.)
of temperature, expressed in English measure
and English Troy weight, 490
No. VII.--TABLES of the Specific Gravities of
different bodies, 491
No. VIII.--ADDITIONAL.--RULES for Calculating
the Absolute Gravity in English Troy
Weight of a Cubic Foot and Inch, English
Measure, of any Substance whose Specific Gravity
is known, 505
No. IX.--TABLES for Converting Ounces, Drams,
and Grains, Troy, into Decimals of the Troy
Pound of 12 Ounces, and for Converting Decimals
of the Pound Troy into Ounces, &c. 508
No. X.--TABLE of the English Cubical Inches and
Decimals corresponding to a determinate Troy
Weight of Distilled Water at the Temperature
of 55 deg., calculated from Everard's experiment, 511
ELEMENTS
OF
CHEMISTRY.
PART I.
Of the Formation and Decomposition of Aeriform Fluids--of the
Combustion of Simple Bodies--and the Formation of Acids.
CHAP. I.
_Of the Combinations of Caloric, and the Formation of Elastic Aeriform
Fluids._
That every body, whether solid or fluid, is augmented in all its
dimensions by any increase of its sensible heat, was long ago fully
established as a physical axiom, or universal proposition, by the
celebrated Boerhaave. Such facts as have been adduced for controverting
the generality of this principle offer only fallacious results, or, at
least, such as are so complicated with foreign circumstances as to
mislead the judgment: But, when we separately consider the effects, so
as to deduce each from the cause to which they separately belong, it is
easy to perceive that the separation of particles by heat is a constant
and general law of nature.
When we have heated a solid body to a certain degree, and have thereby
caused its particles to separate from each other, if we allow the body
to cool, its particles again approach each other in the same proportion
in which they were separated by the increased temperature; the body
returns through the same degrees of expansion which it before extended
through; and, if it be brought back to the same temperature from which
we set out at the commencement of the experiment, it recovers exactly
the same dimensions which it formerly occupied. But, as we are still
very far from being able to arrive at the degree of absolute cold, or
deprivation of all heat, being unacquainted with any degree of coldness
which we cannot suppose capable of still farther augmentation, it
follows, that we are still incapable of causing the ultimate particles
of bodies to approach each other as near as is possible; and,
consequently, that the particles of all bodies do not touch each other
in any state hitherto known, which, tho' a very singular conclusion, is
yet impossible to be denied.
It is supposed, that, since the particles of bodies are thus continually
impelled by heat to separate from each other, they would have no
connection between themselves; and, of consequence, that there could be
no solidity in nature, unless they were held together by some other
power which tends to unite them, and, so to speak, to chain them
together; which power, whatever be its cause, or manner of operation, we
name Attraction.
Thus the particles of all bodies may be considered as subjected to the
action of two opposite powers, the one repulsive, the other attractive,
between which they remain in equilibrio. So long as the attractive force
remains stronger, the body must continue in a state of solidity; but if,
on the contrary, heat has so far removed these particles from each
other, as to place them beyond the sphere of attraction, they lose the
adhesion they before had with each other, and the body ceases to be
solid.
Water gives us a regular and constant example of these facts; whilst
below Zero[2] of the French thermometer, or 32 deg. of Fahrenheit, it
remains solid, and is called ice. Above that degree of temperature, its
particles being no longer held together by reciprocal attraction, it
becomes liquid; and, when we raise its temperature above 80 deg., (212
deg.) its particles, giving way to the repulsion caused by the heat,
assume the state of vapour or gas, and the water is changed into an
aeriform fluid.
The same may be affirmed of all bodies in nature: They are either solid
or liquid, or in the state of elastic aeriform vapour, according to the
proportion which takes place between the attractive force inherent in
their particles, and the repulsive power of the heat acting upon these;
or, what amounts to the same thing, in proportion to the degree of heat
to which they are exposed.
It is difficult to comprehend these phenomena, without admitting them as
the effects of a real and material substance, or very subtile fluid,
which, insinuating itself between the particles of bodies, separates
them from each other; and, even allowing the existence of this fluid to
be hypothetical, we shall see in the sequel, that it explains the
phenomena of nature in a very satisfactory manner.
This substance, whatever it is, being the cause of heat, or, in other
words, the sensation which we call _warmth_ being caused by the
accumulation of this substance, we cannot, in strict language,
distinguish it by the term _heat_; because the same name would then very
improperly express both cause and effect. For this reason, in the memoir
which I published in 1777[3], I gave it the names of _igneous fluid_ and
_matter of heat_. And, since that time, in the work[4] published by Mr
de Morveau, Mr Berthollet, Mr de Fourcroy, and myself, upon the
reformation of chemical nomenclature, we thought it necessary to banish
all periphrastic expressions, which both lengthen physical language, and
render it more tedious and less distinct, and which even frequently does
not convey sufficiently just ideas of the subject intended. Wherefore,
we have distinguished the cause of heat, or that exquisitely elastic
fluid which produces it, by the term of _caloric_. Besides, that this
expression fulfils our object in the system which we have adopted, it
possesses this farther advantage, that it accords with every species of
opinion, since, strictly speaking, we are not obliged to suppose this to
be a real substance; it being sufficient, as will more clearly appear in
the sequel of this work, that it be considered as the repulsive cause,
whatever that may be, which separates the particles of matter from each
other; so that we are still at liberty to investigate its effects in an
abstract and mathematical manner.
In the present state of our knowledge, we are unable to determine
whether light be a modification of caloric, or if caloric be, on the
contrary, a modification of light. This, however, is indisputable, that,
in a system where only decided facts are admissible, and where we avoid,
as far as possible, to suppose any thing to be that is not really known
to exist, we ought provisionally to distinguish, by distinct terms, such
things as are known to produce different effects. We therefore
distinguish light from caloric; though we do not therefore deny that
these have certain qualities in common, and that, in certain
circumstances, they combine with other bodies almost in the same manner,
and produce, in part, the same effects.
What I have already said may suffice to determine the idea affixed to
the word _caloric_; but there remains a more difficult attempt, which
is, to give a just conception of the manner in which caloric acts upon
other bodies. Since this subtile matter penetrates through the pores of
all known substances; since there are no vessels through which it cannot
escape, and, consequently, as there are none which are capable of
retaining it, we can only come at the knowledge of its properties by
effects which are fleeting, and difficultly ascertainable. It is in
these things which we neither see nor feel, that it is especially
necessary to guard against the extravagancy of our imagination, which
forever inclines to step beyond the bounds of truth, and is very
difficultly restrained within the narrow line of facts.
We have already seen, that the same body becomes solid, or fluid, or
aeriform, according to the quantity of caloric by which it is
penetrated; or, to speak more strictly, according as the repulsive force
exerted by the caloric is equal to, stronger, or weaker, than the
attraction of the particles of the body it acts upon.
But, if these two powers only existed, bodies would become liquid at an
indivisible degree of the thermometer, and would almost instantaneously
pass from the solid state of aggregation to that of aeriform elasticity.
Thus water, for instance, at the very moment when it ceases to be ice,
would begin to boil, and would be transformed into an aeriform fluid,
having its particles scattered indefinitely through the surrounding
space. That this does not happen, must depend upon the action of some
third power. The pressure of the atmosphere prevents this separation,
and causes the water to remain in the liquid state till it be raised to
80 deg. of temperature (212 deg.) above zero of the French thermometer,
the quantity of caloric which it receives in the lowest temperature being
insufficient to overcome the pressure of the atmosphere.
Whence it appears that, without this atmospheric pressure, we should not
have any permanent liquid, and should only be able to see bodies in that
state of existence in the very instant of melting, as the smallest
additional caloric would instantly separate their particles, and
dissipate them through the surrounding medium. Besides, without this
atmospheric pressure, we should not even have any aeriform fluids,
strictly speaking, because the moment the force of attraction is
overcome by the repulsive power of the caloric, the particles would
separate themselves indefinitely, having nothing to give limits to their
expansion, unless their own gravity might collect them together, so as
to form an atmosphere.
Simple reflection upon the most common experiments is sufficient to
evince the truth of these positions. They are more particularly proved
by the following experiment, which I published in the Memoirs of the
French Academy for 1777, p. 426.
Having filled with sulphuric ether[5] a small narrow glass vessel, A,
(Plate VII. Fig. 17.), standing upon its stalk P, the vessel, which is
from twelve to fifteen lines diameter, is to be covered by a wet
bladder, tied round its neck with several turns of strong thread; for
greater security, fix a second bladder over the first. The vessel should
be filled in such a manner with the ether, as not to leave the smallest
portion of air between the liquor and the bladder. It is now to be
placed under the recipient BCD of an air-pump, of which the upper part B
ought to be fitted with a leathern lid, through which passes a wire EF,
having its point F very sharp; and in the same receiver there ought to
be placed the barometer GH. The whole being thus disposed, let the
recipient be exhausted, and then, by pushing down the wire EF, we make a
hole in the bladder. Immediately the ether begins to boil with great
violence, and is changed into an elastic aeriform fluid, which fills the
receiver. If the quantity of ether be sufficient to leave a few drops in
the phial after the evaporation is finished, the elastic fluid produced
will sustain the mercury in the barometer attached to the air-pump, at
eight or ten inches in winter, and from twenty to twenty-five in
summer[6]. To render this experiment more complete, we may introduce a
small thermometer into the phial A, containing the ether, which will
descend considerably during the evaporation.
The only effect produced in this experiment is, the taking away the
weight of the atmosphere, which, in its ordinary state, presses on the
surface of the ether; and the effects resulting from this removal
evidently prove, that, in the ordinary temperature of the earth, ether
would always exist in an aeriform state, but for the pressure of the
atmosphere, and that the passing of the ether from the liquid to the
aeriform state is accompanied by a considerable lessening of heat;
because, during the evaporation, a part of the caloric, which was before
in a free state, or at least in equilibrio in the surrounding bodies,
combines with the ether, and causes it to assume the aeriform state.
The same experiment succeeds with all evaporable fluids, such as
alkohol, water, and even mercury; with this difference, that the
atmosphere formed in the receiver by alkohol only supports the attached
barometer about one inch in winter, and about four or five inches in
summer; that formed by water, in the same situation, raises the mercury
only a few lines, and that by quicksilver but a few fractions of a line.
There is therefore less fluid evaporated from alkohol than from ether,
less from water than from alkohol, and still less from mercury than from
either; consequently there is less caloric employed, and less cold
produced, which quadrates exactly with the results of these experiments.
Another species of experiment proves very evidently that the aeriform
state is a modification of bodies dependent on the degree of
temperature, and on the pressure which these bodies undergo. In a Memoir
read by Mr de la Place and me to the Academy in 1777, which has not been
printed, we have shown, that, when ether is subjected to a pressure
equal to twenty-eight inches of the barometer, or about the medium
pressure of the atmosphere, it boils at the temperature of about 32 deg.
(104 deg.), or 33 deg. (106.25 deg.), of the thermometer. Mr de Luc, who
has made similar experiments with spirit of wine, finds it boils at 67
deg. (182.75 deg.). And all the world knows that water boils at 80 deg.
(212 deg.). Now, boiling being only the evaporation of a liquid, or the
moment of its passing from the fluid to the aeriform state, it is
evident that, if we keep ether continually at the temperature of 33 deg.
(106.25 deg.), and under the common pressure of the atmosphere, we shall
have it always in an elastic aeriform state; and that the same thing
will happen with alkohol when above 67 deg. (182.75 deg.), and with
water when above 80 deg. (212 deg.); all which are perfectly conformable
to the following experiment[7].
I filled a large vessel ABCD (Plate VII. Fig. 16.) with water, at 35 deg.
(110.75 deg.), or 36 deg. (113 deg.); I suppose the vessel transparent,
that we may see what takes place in the experiment; and we can easily
hold the hands in water at that temperature without inconvenience. Into
it I plunged some narrow necked bottles F, G, which were filled with the
water, after which they were turned up, so as to rest on their mouths on
the bottom of the vessel. Having next put some ether into a very small
matrass, with its neck a b c, twice bent as in the Plate, I plunged this
matrass into the water, so as to have its neck inserted into the mouth
of one of the bottles F. Immediately upon feeling the effects of the
heat communicated to it by the water in the vessel ABCD it began to
boil; and the caloric entering into combination with it, changed it into
elastic aeriform fluid, with which I filled several bottles
successively, F, G, &c.
This is not the place to enter upon the examination of the nature and
properties of this aeriform fluid, which is extremely inflammable; but,
confining myself to the object at present in view, without anticipating
circumstances, which I am not to suppose the reader to know, I shall
only observe, that the ether, from this experiment, is almost only
capable of existing in the aeriform state in our world; for, if the
weight of our atmosphere was only equal to between 20 and 24 inches of
the barometer, instead of 28 inches, we should never be able to obtain
ether in the liquid state, at least in summer; and the formation of
ether would consequently be impossible upon mountains of a moderate
degree of elevation, as it would be converted into gas immediately upon
being produced, unless we employed recipients of extraordinary strength,
together with refrigeration and compression. And, lastly, the
temperature of the blood being nearly that at which ether passes from
the liquid to the aeriform state, it must evaporate in the primae viae,
and consequently it is very probable the medical properties of this
fluid depend chiefly upon its mechanical effect.
These experiments succeed better with nitrous ether, because it
evaporates in a lower temperature than sulphuric ether. It is more
difficult to obtain alkohol in the aeriform state; because, as it
requires 67 deg. (182.75 deg.) to reduce it to vapour, the water of the
bath must be almost boiling, and consequently it is impossible to plunge
the hands into it at that temperature.
It is evident that, if water were used in the foregoing experiment, it
would be changed into gas, when exposed to a temperature superior to
that at which it boils. Although thoroughly convinced of this, Mr de la
Place and myself judged it necessary to confirm it by the following
direct experiment. We filled a glass jar A, (Plate VII. Fig. 5.) with
mercury, and placed it with its mouth downwards in a dish B, likewise
filled with mercury, and having introduced about two gross of water into
the jar, which rose to the top of the mercury at CD; we then plunged the
whole apparatus into an iron boiler EFGH, full of boiling sea-water of
the temperature of 85 deg. (123.25 deg.), placed upon the furnace GHIK.
Immediately upon the water over the mercury attaining the temperature of
80 deg. (212 deg.), it began to boil; and, instead of only filling the
small space ACD, it was converted into an aeriform fluid, which filled
the whole jar; the mercury even descended below the surface of that in
the dish B; and the jar must have been overturned, if it had not been
very thick and heavy, and fixed to the dish by means of iron-wire.
Immediately after withdrawing the apparatus from the boiler, the vapour
in the jar began to condense, and the mercury rose to its former
station; but it returned again to the aeriform state a few seconds after
replacing the apparatus in the boiler.
We have thus a certain number of substances, which are convertible into
elastic aeriform fluids by degrees of temperature, not much superior to
that of our atmosphere. We shall afterwards find that there are several
others which undergo the same change in similar circumstances, such as
muriatic or marine acid, ammoniac or volatile alkali, the carbonic acid
or fixed air, the sulphurous acid, &c. All of these are permanently
elastic in or about the mean temperature of the atmosphere, and under
its common pressure.
All these facts, which could be easily multiplied if necessary, give me
full right to assume, as a general principle, that almost every body in
nature is susceptible of three several states of existence, solid,
liquid, and aeriform, and that these three states of existence depend
upon the quantity of caloric combined with the body. Henceforwards I
shall express these elastic aeriform fluids by the generic term _gas_;
and in each species of gas I shall distinguish between the caloric,
which in some measure serves the purpose of a solvent, and the
substance, which in combination with the caloric, forms the base of the
gas.
To these bases of the different gases, which are hitherto but little
known, we have been obliged to assign names; these I shall point out in
Chap. IV. of this work, when I have previously given an account of the
phenomena attendant upon the heating and cooling of bodies, and when I
have established precise ideas concerning the composition of our
atmosphere.
We have already shown, that the particles of every substance in nature
exist in a certain state of equilibrium, between that attraction which
tends to unite and keep the particles together, and the effects of the
caloric which tends to separate them. Hence the caloric not only
surrounds the particles of all bodies on every side, but fills up every
interval which the particles of bodies leave between each other. We may
form an idea of this, by supposing a vessel filled with small spherical
leaden bullets, into which a quantity of fine sand is poured, which,
insinuating into the intervals between the bullets, will fill up every
void. The balls, in this comparison, are to the sand which surrounds
them exactly in the same situation as the particles of bodies are with
respect to the caloric; with this difference only, that the balls are
supposed to touch each other, whereas the particles of bodies are not in
contact, being retained at a small distance from each other, by the
caloric.
If, instead of spherical balls, we substitute solid bodies of a
hexahedral, octohedral, or any other regular figure, the capacity of the
intervals between them will be lessened, and consequently will no longer
contain the same quantity of sand. The same thing takes place, with
respect to natural bodies; the intervals left between their particles
are not of equal capacity, but vary in consequence of the different
figures and magnitude of their particles, and of the distance at which
these particles are maintained, according to the existing proportion
between their inherent attraction, and the repulsive force exerted upon
them by the caloric.
In this manner we must understand the following expression, introduced
by the English philosophers, who have given us the first precise ideas
upon this subject; _the capacity of bodies for containing the matter of
heat_. As comparisons with sensible objects are of great use in
assisting us to form distinct notions of abstract ideas, we shall
endeavour to illustrate this, by instancing the phenomena which take
place between water and bodies which are wetted and penetrated by it,
with a few reflections.
If we immerge equal pieces of different kinds of wood, suppose cubes of
one foot each, into water, the fluid gradually insinuates itself into
their pores, and the pieces of wood are augmented both in weight and
magnitude: But each species of wood will imbibe a different quantity of
water; the lighter and more porous woods will admit a larger, the
compact and closer grained will admit of a lesser quantity; for the
proportional quantities of water imbibed by the pieces will depend upon
the nature of the constituent particles of the wood, and upon the
greater or lesser affinity subsisting between them and water. Very
resinous wood, for instance, though it may be at the same time very
porous, will admit but little water. We may therefore say, that the
different kinds of wood possess different capacities for receiving
water; we may even determine, by means of the augmentation of their
weights, what quantity of water they have actually absorbed; but, as we
are ignorant how much water they contained, previous to immersion, we
cannot determine the absolute quantity they contain, after being taken
out of the water.
The same circumstances undoubtedly take place, with bodies that are
immersed in caloric; taking into consideration, however, that water is
an incompressible fluid, whereas caloric is, on the contrary, endowed
with very great elasticity; or, in other words, the particles of caloric
have a great tendency to separate from each other, when forced by any
other power to approach; this difference must of necessity occasion
very considerable diversities in the results of experiments made upon
these two substances.
Having established these clear and simple propositions, it will be very
easy to explain the ideas which ought to be affixed to the following
expressions, which are by no means synonimous, but possess each a strict
and determinate meaning, as in the following definitions:
_Free caloric_, is that which is not combined in any manner with any
other body. But, as we live in a system to which caloric has a very
strong adhesion, it follows that we are never able to obtain it in the
state of absolute freedom.
_Combined caloric_, is that which is fixed in bodies by affinity or
elective attraction, so as to form part of the substance of the body,
even part of its solidity.
By the expression _specific caloric_ of bodies, we understand the
respective quantities of caloric requisite for raising a number of
bodies of the same weight to an equal degree of temperature. This
proportional quantity of caloric depends upon the distance between the
constituent particles of bodies, and their greater or lesser degrees of
cohesion; and this distance, or rather the space or void resulting from
it, is, as I have already observed, called the _capacity of bodies for
containing caloric_.
_Heat_, considered as a sensation, or, in other words, sensible heat, is
only the effect produced upon our sentient organs, by the motion or
passage of caloric, disengaged from the surrounding bodies. In general,
we receive impressions only in consequence of motion, and we might
establish it as an axiom, _That_, WITHOUT MOTION, THERE IS NO SENSATION.
This general principle applies very accurately to the sensations of heat
and cold: When we touch a cold body, the caloric which always tends to
become in equilibrio in all bodies, passes from our hand into the body
we touch, which gives us the feeling or sensation of cold. The direct
contrary happens, when we touch a warm body, the caloric then passing
from the body into our hand, produces the sensation of heat. If the hand
and the body touched be of the same temperature, or very nearly so, we
receive no impression, either of heat or cold, because there is no
motion or passage of caloric; and thus no sensation can take place,
without some correspondent motion to occasion it.
When the thermometer rises, it shows, that free caloric is entering into
the surrounding bodies: The thermometer, which is one of these, receives
its share in proportion to its mass, and to the capacity which it
possesses for containing caloric. The change therefore which takes place
upon the thermometer, only announces a change of place of the caloric
in those bodies, of which the thermometer forms one part; it only
indicates the portion of caloric received, without being a measure of
the whole quantity disengaged, displaced, or absorbed.
The most simple and most exact method for determining this latter point,
is that described by Mr de la Place, in the Memoirs of the Academy, No.
1780, p. 364; a summary explanation of which will be found towards the
conclusion of this work. This method consists in placing a body, or a
combination of bodies, from which caloric is disengaging, in the midst
of a hollow sphere of ice; and the quantity of ice melted becomes an
exact measure of the quantity of caloric disengaged. It is possible, by
means of the apparatus which we have caused to be constructed upon this
plan, to determine, not as has been pretended, the capacity of bodies
for containing heat, but the ratio of the increase or diminution of
capacity produced by determinate degrees of temperature. It is easy with
the same apparatus, by means of divers combinations of experiments, to
determine the quantity of caloric requisite for converting solid
substances into liquids, and liquids into elastic aeriform fluids; and,
_vice versa_, what quantity of caloric escapes from elastic vapours in
changing to liquids, and what quantity escapes from liquids during their
conversion into solids. Perhaps, when experiments have been made with
sufficient accuracy, we may one day be able to determine the
proportional quantity of caloric, necessary for producing the several
species of gasses. I shall hereafter, in a separate chapter, give an
account of the principal results of such experiments as have been made
upon this head.
It remains, before finishing this article, to say a few words relative
to the cause of the elasticity of gasses, and of fluids in the state of
vapour. It is by no means difficult to perceive that this elasticity
depends upon that of caloric, which seems to be the most eminently
elastic body in nature. Nothing is more readily conceived, than that one
body should become elastic by entering into combination with another
body possessed of that quality. We must allow that this is only an
explanation of elasticity, by an assumption of elasticity, and that we
thus only remove the difficulty one step farther, and that the nature of
elasticity, and the reason for caloric being elastic, remains still
unexplained. Elasticity in the abstract is nothing more than that
quality of the particles of bodies by which they recede from each other
when forced together. This tendency in the particles of caloric to
separate, takes place even at considerable distances. We shall be
satisfied of this, when we consider that air is susceptible of
undergoing great compression, which supposes that its particles were
previously very distant from each other; for the power of approaching
together certainly supposes a previous distance, at least equal to the
degree of approach. Consequently, those particles of the air, which are
already considerably distant from each other, tend to separate still
farther. In fact, if we produce Boyle's vacuum in a large receiver, the
very last portion of air which remains spreads itself uniformly through
the whole capacity of the vessel, however large, fills it completely
throughout, and presses every where against its sides: We cannot,
however, explain this effect, without supposing that the particles make
an effort to separate themselves on every side, and we are quite
ignorant at what distance, or what degree of rarefaction, this effort
ceases to act.
Here, therefore, exists a true repulsion between the particles of
elastic fluids; at least, circumstances take place exactly as if such a
repulsion actually existed; and we have very good right to conclude,
that the particles of caloric mutually repel each other. When we are
once permitted to suppose this repelling force, the _rationale_ of the
formation of gasses, or aeriform fluids, becomes perfectly simple; tho'
we must, at the same time, allow, that it is extremely difficult to form
an accurate conception of this repulsive force acting upon very minute
particles placed at great distances from each other.
It is, perhaps, more natural to suppose, that the particles of caloric
have a stronger mutual attraction than those of any other substance, and
that these latter particles are forced asunder in consequence of this
superior attraction between the particles of the caloric, which forces
them between the particles of other bodies, that they may be able to
reunite with each other. We have somewhat analogous to this idea in the
phenomena which occur when a dry sponge is dipt into water: The sponge
swells; its particles separate from each other; and all its intervals
are filled up by the water. It is evident, that the sponge, in the act
of swelling, has acquired a greater capacity for containing water than
it had when dry. But we cannot certainly maintain, that the introduction
of water between the particles of the sponge has endowed them with a
repulsive power, which tends to separate them from each other; on the
contrary, the whole phenomena are produced by means of attractive
powers; and these are, _first_, The gravity of the water, and the power
which it exerts on every side, in common with all other fluids; _2dly_,
The force of attraction which takes place between the particles of the
water, causing them to unite together; _3dly_, The mutual attraction of
the particles of the sponge with each other; and, _lastly_, The
reciprocal attraction which exists between the particles of the sponge
and those of the water. It is easy to understand, that the explanation
of this fact depends upon properly appreciating the intensity of, and
connection between, these several powers. It is probable, that the
separation of the particles of bodies, occasioned by caloric, depends in
a similar manner upon a certain combination of different attractive
powers, which, in conformity with the imperfection of our knowledge, we
endeavour to express by saying, that caloric communicates a power of
repulsion to the particles of bodies.
FOOTNOTES:
[2] Whenever the degree of heat occurs in this work, it is stated by the
author according to Reaumur's scale. The degrees within brackets are the
correspondent degrees of Fahrenheit's scale, added by the translator. E.
[3] Collections of the French Academy of Sciences for that year, p. 420.
[4] Chemical Nomenclature.
[5] As I shall afterwards give a definition, and explain the properties
of the liquor called _ether_, I shall only premise here, that it is a
very volatile inflammable liquor, having a considerably smaller specific
gravity than water, or even spirit of wine.--A.
[6] It would have been more satisfactory if the Author had specified the
degrees of the thermometer at which these heights of the mercury in the
barometer are produced.
[7] Vide Memoirs of the French Academy, anno 1780, p. 335.--A.
CHAP. II.
_General Views relative to the Formation and Composition of our
Atmosphere._
These views which I have taken of the formation of elastic aeriform
fluids or gasses, throw great light upon the original formation of the
atmospheres of the planets, and particularly that of our earth. We
readily conceive, that it must necessarily consist of a mixture of the
following substances: _First_, Of all bodies that are susceptible of
evaporation, or, more strictly speaking, which are capable of retaining
the state of aeriform elasticity in the temperature of our atmosphere,
and under a pressure equal to that of a column of twenty-eight inches of
quicksilver in the barometer; and, _secondly_, Of all substances,
whether liquid or solid, which are capable of being dissolved by this
mixture of different gasses.
The better to determine our ideas relating to this subject, which has
not hitherto been sufficiently considered, let us, for a moment,
conceive what change would take place in the various substances which
compose our earth, if its temperature were suddenly altered. If, for
instance, we were suddenly transported into the region of the planet
Mercury, where probably the common temperature is much superior to that
of boiling water, the water of the earth, and all the other fluids which
are susceptible of the gasseous state, at a temperature near to that of
boiling water, even quicksilver itself, would become rarified; and all
these substances would be changed into permanent aeriform fluids or
gasses, which would become part of the new atmosphere. These new species
of airs or gasses would mix with those already existing, and certain
reciprocal decompositions and new combinations would take place, until
such time as all the elective attractions or affinities subsisting
amongst all these new and old gasseous substances had operated fully;
after which, the elementary principles composing these gasses, being
saturated, would remain at rest. We must attend to this, however, that,
even in the above hypothetical situation, certain bounds would occur to
the evaporation of these substances, produced by that very evaporation
itself; for as, in proportion to the increase of elastic fluids, the
pressure of the atmosphere would be augmented, as every degree of
pressure tends, in some measure, to prevent evaporation, and as even the
most evaporable fluids can resist the operation of a very high
temperature without evaporating, if prevented by a proportionally
stronger compression, water and all other liquids being able to sustain
a red heat in Papin's digester; we must admit, that the new atmosphere
would at last arrive at such a degree of weight, that the water which
had not hitherto evaporated would cease to boil, and, of consequence,
would remain liquid; so that, even upon this supposition, as in all
others of the same nature, the increasing gravity of the atmosphere
would find certain limits which it could not exceed. We might even
extend these reflections greatly farther, and examine what change might
be produced in such situations upon stones, salts, and the greater part
of the fusible substances which compose the mass of our earth. These
would be softened, fused, and changed into fluids, &c.: But these
speculations carry me from my object, to which I hasten to return.
By a contrary supposition to the one we have been forming, if the earth
were suddenly transported into a very cold region, the water which at
present composes our seas, rivers, and springs, and probably the greater
number of the fluids we are acquainted with, would be converted into
solid mountains and hard rocks, at first diaphanous and homogeneous,
like rock crystal, but which, in time, becoming mixed with foreign and
heterogeneous substances, would become opake stones of various colours.
In this case, the air, or at least some part of the aeriform fluids
which now compose the mass of our atmosphere, would doubtless lose its
elasticity for want of a sufficient temperature to retain them in that
state: They would return to the liquid state of existence, and new
liquids would be formed, of whose properties we cannot, at present, form
the most distant idea.
These two opposite suppositions give a distinct proof of the following
corollaries: _First_, That _solidity_, _liquidity_, and _aeriform
elasticity_, are only three different states of existence of the same
matter, or three particular modifications which almost all substances
are susceptible of assuming successively, and which solely depend upon
the degree of temperature to which they are exposed; or, in other words,
upon the quantity of caloric with which they are penetrated[8]. _2dly_,
That it is extremely probable that air is a fluid naturally existing in
a state of vapour; or, as we may better express it, that our atmosphere
is a compound of all the fluids which are susceptible of the vaporous
or permanently elastic state, in the usual temperature, and under the
common pressure. _3dly_, That it is not impossible we may discover, in
our atmosphere, certain substances naturally very compact, even metals
themselves; as a metallic substance, for instance, only a little more
volatile than mercury, might exist in that situation.
Amongst the fluids with which we are acquainted, some, as water and
alkohol, are susceptible of mixing with each other in all proportions;
whereas others, on the contrary, as quicksilver, water, and oil, can
only form a momentary union; and, after being mixed together, separate
and arrange themselves according to their specific gravities. The same
thing ought to, or at least may, take place in the atmosphere. It is
possible, and even extremely probable, that, both at the first creation,
and every day, gasses are formed, which are difficultly miscible with
atmospheric air, and are continually separating from it. If these gasses
be specifically lighter than the general atmospheric mass, they must, of
course, gather in the higher regions, and form strata that float upon
the common air. The phenomena which accompany igneous meteors induce me
to believe, that there exists in the upper parts of our atmosphere a
stratum of inflammable fluid in contact with those strata of air which
produce the phenomena of the aurora borealis and other fiery meteors.--I
mean hereafter to pursue this subject in a separate treatise.
FOOTNOTES:
[8] The degree of pressure which they undergo must be taken into
account. E.
CHAP. III.
_Analysis of Atmospheric Air, and its Division into two Elastic Fluids;
the one fit for Respiration, the other incapable of being respired._
From what has been premised, it follows, that our atmosphere is composed
of a mixture of every substance capable of retaining the gasseous or
aeriform state in the common temperature, and under the usual pressure
which it experiences. These fluids constitute a mass, in some measure
homogeneous, extending from the surface of the earth to the greatest
height hitherto attained, of which the density continually decreases in
the inverse ratio of the superincumbent weight. But, as I have before
observed, it is possible that this first stratum is surmounted by
several others consisting of very different fluids.
Our business, in this place, is to endeavour to determine, by
experiments, the nature of the elastic fluids which compose the inferior
stratum of air which we inhabit. Modern chemistry has made great
advances in this research; and it will appear by the following details
that the analysis of atmospherical air has been more rigorously
determined than that of any other substance of the class. Chemistry
affords two general methods of determining the constituent principles of
bodies, the method of analysis, and that of synthesis. When, for
instance, by combining water with alkohol, we form the species of liquor
called, in commercial language, brandy or spirit of wine, we certainly
have a right to conclude, that brandy, or spirit of wine, is composed of
alkohol combined with water. We can produce the same result by the
analytical method; and in general it ought to be considered as a
principle in chemical science, never to rest satisfied without both
these species of proofs.
We have this advantage in the analysis of atmospherical air, being able
both to decompound it, and to form it a new in the most satisfactory
manner. I shall, however, at present confine myself to recount such
experiments as are most conclusive upon this head; and I may consider
most of these as my own, having either first invented them, or having
repeated those of others, with the intention of analysing atmospherical
air, in perfectly new points of view.
I took a matrass (A, fig. 14. plate II.) of about 36 cubical inches
capacity, having a long neck B C D E, of six or seven lines internal
diameter, and having bent the neck as in Plate IV. Fig. 2. so as to
allow of its being placed in the furnace M M N N, in such a manner that
the extremity of its neck E might be inserted under a bell-glass F G,
placed in a trough of quicksilver R R S S; I introduced four ounces of
pure mercury into the matrass, and, by means of a syphon, exhausted the
air in the receiver F G, so as to raise the quicksilver to L L, and I
carefully marked the height at which it stood by pasting on a slip of
paper. Having accurately noted the height of the thermometer and
barometer, I lighted a fire in the furnace M M N N, which I kept up
almost continually during twelve days, so as to keep the quicksilver
always almost at its boiling point. Nothing remarkable took place during
the first day: The Mercury, though not boiling, was continually
evaporating, and covered the interior surface of the vessels with small
drops, at first very minute, which gradually augmenting to a sufficient
size, fell back into the mass at the bottom of the vessel. On the second
day, small red particles began to appear on the surface of the mercury,
which, during the four or five following days, gradually increased in
size and number; after which they ceased to increase in either respect.
At the end of twelve days, seeing that the calcination of the mercury
did not at all increase, I extinguished the fire, and allowed the
vessels to cool. The bulk of air in the body and neck of the matrass,
and in the bell-glass, reduced to a medium of 28 inches of the
barometer and 10 deg. (54.5 deg.) of the thermometer, at the commencement
of the experiment was about 50 cubical inches. At the end of the
experiment the remaining air, reduced to the same medium pressure and
temperature, was only between 42 and 43 cubical inches; consequently it
had lost about 1/6 of its bulk. Afterwards, having collected all the
red particles, formed during the experiment, from the running mercury
in which they floated, I found these to amount to 45 grains.
I was obliged to repeat this experiment several times, as it is
difficult in one experiment both to preserve the whole air upon which we
operate, and to collect the whole of the red particles, or calx of
mercury, which is formed during the calcination. It will often happen in
the sequel, that I shall, in this manner, give in one detail the results
of two or three experiments of the same nature.
The air which remained after the calcination of the mercury in this
experiment, and which was reduced to 5/6 of its former bulk, was no
longer fit either for respiration or for combustion; animals being
introduced into it were suffocated in a few seconds, and when a taper
was plunged into it, it was extinguished as if it had been immersed into
water.
In the next place, I took the 45 grains of red matter formed during this
experiment, which I put into a small glass retort, having a proper
apparatus for receiving such liquid, or gasseous product, as might be
extracted: Having applied a fire to the retort in a furnace, I observed
that, in proportion as the red matter became heated, the intensity of
its colour augmented. When the retort was almost red hot, the red matter
began gradually to decrease in bulk, and in a few minutes after it
disappeared altogether; at the same time 41-1/2 grains of running
mercury were collected in the recipient, and 7 or 8 cubical inches of
elastic fluid, greatly more capable of supporting both respiration and
combustion than atmospherical air, were collected in the bell-glass.
A part of this air being put into a glass tube of about an inch
diameter, showed the following properties: A taper burned in it with a
dazzling splendour, and charcoal, instead of consuming quietly as it
does in common air, burnt with a flame, attended with a decrepitating
noise, like phosphorus, and threw out such a brilliant light that the
eyes could hardly endure it. This species of air was discovered almost
at the same time by Mr Priestley, Mr Scheele, and myself. Mr Priestley
gave it the name of _dephlogisticated air_, Mr Scheele called it
_empyreal air_. At first I named it _highly respirable air_, to which
has since been substituted the term of _vital air_. We shall presently
see what we ought to think of these denominations.
In reflecting upon the circumstances of this experiment, we readily
perceive, that the mercury, during its calcination, absorbs the
salubrious and respirable part of the air, or, to speak more strictly,
the base of this respirable part; that the remaining air is a species of
mephitis, incapable of supporting combustion or respiration; and
consequently that atmospheric air is composed of two elastic fluids of
different and opposite qualities. As a proof of this important truth, if
we recombine these two elastic fluids, which we have separately obtained
in the above experiment, viz. the 42 cubical inches of mephitis, with
the 8 cubical inches of respirable air, we reproduce an air precisely
similar to that of the atmosphere, and possessing nearly the same power
of supporting combustion and respiration, and of contributing to the
calcination of metals.
Although this experiment furnishes us with a very simple means of
obtaining the two principal elastic fluids which compose our atmosphere,
separate from each other, yet it does not give us an exact idea of the
proportion in which these two enter into its composition: For the
attraction of mercury to the respirable part of the air, or rather to
its base, is not sufficiently strong to overcome all the circumstances
which oppose this union. These obstacles are the mutual adhesion of the
two constituent parts of the atmosphere for each other, and the elective
attraction which unites the base of vital air with caloric; in
consequence of these, when the calcination ends, or is at least carried
as far as is possible, in a determinate quantity of atmospheric air,
there still remains a portion of respirable air united to the mephitis,
which the mercury cannot separate. I shall afterwards show, that, at
least in our climate, the atmospheric air is composed of respirable and
mephitic airs, in the proportion of 27 and 73; and I shall then discuss
the causes of the uncertainty which still exists with respect to the
exactness of that proportion.
Since, during the calcination of mercury, air is decomposed, and the
base of its respirable part is fixed and combined with the mercury, it
follows, from the principles already established, that caloric and light
must be disengaged during the process: But the two following causes
prevent us from being sensible of this taking place: As the calcination
lasts during several days, the disengagement of caloric and light,
spread out in a considerable space of time, becomes extremely small for
each particular moment of that time, so as not to be perceptible; and,
in the next place, the operation being carried on by means of fire in a
furnace, the heat produced by the calcination itself becomes confounded
with that proceeding from the furnace. I might add the respirable part
of the air, or rather its base, in entering into combination with the
mercury, does not part with all the caloric which it contained, but
still retains a part of it after forming the new compound; but the
discussion of this point, and its proofs from experiment, do not belong
to this part of our subject.
It is, however, easy to render this disengagement of caloric and light
evident to the senses, by causing the decomposition of air to take place
in a more rapid manner. And for this purpose, iron is excellently
adapted, as it possesses a much stronger affinity for the base of
respirable air than mercury. The elegant experiment of Mr Ingenhouz,
upon the combustion of iron, is well known. Take a piece of fine iron
wire, twisted into a spiral, (BC, Plate IV. Fig. 17.) fix one of its
extremities B into the cork A, adapted to the neck of the bottle DEFG,
and fix to the other extremity of the wire C, a small morsel of tinder.
Matters being thus prepared, fill the bottle DEFG with air deprived of
its mephitic part; then light the tinder, and introduce it quickly with
the wire upon which it is fixed, into the bottle which you stop up with
the cork A, as is shown in the figure (17 Plate IV.) The instant the
tinder comes into contact with the vital air it begins to burn with
great intensity; and, communicating the inflammation to the iron-wire,
it too takes fire, and burns rapidly, throwing out brilliant sparks,
which fall to the bottom of the vessel in rounded globules, which become
black in cooling, but retain a degree of metallic splendour. The iron
thus burnt is more brittle even than glass, and is easily reduced into
powder, and is still attractable by the magnet, though not so powerfully
as it was before combustion. As Mr Ingenhouz has neither examined the
change produced on iron, nor upon the air by this operation, I have
repeated the experiment under different circumstances, in an apparatus
adapted to answer my particular views, as follows.
Having filled a bell-glass (A, Plate IV. Fig. 3.) of about six pints
measure, with pure air, or the highly respirable part of air, I
transported this jar by means of a very flat vessel, into a quicksilver
bath in the bason BC, and I took care to render the surface of the
mercury perfectly dry both within and without the jar with blotting
paper. I then provided a small capsule of china-ware D, very flat and
open, in which I placed some small pieces of iron, turned spirally, and
arranged in such a way as seemed most favourable for the combustion
being communicated to every part. To the end of one of these pieces of
iron was fixed a small morsel of tinder, to which was added about the
sixteenth part of a grain of phosphorus, and, by raising the bell-glass
a little, the china capsule, with its contents, were introduced into the
pure air. I know that, by this means, some common air must mix with the
pure air in the glass; but this, when it is done dexterously, is so very
trifling, as not to injure the success of the experiment. This being
done, a part of the air is sucked out from the bell-glass, by means of a
syphon GHI, so as to raise the mercury within the glass to EF; and, to
prevent the mercury from getting into the syphon, a small piece of paper
is twisted round its extremity. In sucking out the air, if the motion of
the lungs only be used, we cannot make the mercury rise above an inch or
an inch and a half; but, by properly using the muscles of the mouth, we
can, without difficulty, cause it to rise six or seven inches.
I next took an iron wire, (MN, Plate IV. Fig. 16.) properly bent for the
purpose, and making it red hot in the fire, passed it through the
mercury into the receiver, and brought it in contact with the small
piece of phosphorus attached to the tinder. The phosphorus instantly
takes fire, which communicates to the tinder, and from that to the iron.
When the pieces have been properly arranged, the whole iron burns, even
to the last particle, throwing out a white brilliant light similar to
that of Chinese fireworks. The great heat produced by this combustion
melts the iron into round globules of different sizes, most of which
fall into the China cup; but some are thrown out of it, and swim upon
the surface of the mercury. At the beginning of the combustion, there is
a slight augmentation in the volume of the air in the bell-glass, from
the dilatation caused by the heat; but, presently afterwards, a rapid
diminution of the air takes place, and the mercury rises in the glass;
insomuch that, when the quantity of iron is sufficient, and the air
operated upon is very pure, almost the whole air employed is absorbed.
It is proper to remark in this place, that, unless in making experiments
for the purpose of discovery, it is better to be contented with burning
a moderate quantity of iron; for, when this experiment is pushed too
far, so as to absorb much of the air, the cup D, which floats upon the
quicksilver, approaches too near the bottom of the bell-glass; and the
great heat produced, which is followed by a very sudden cooling,
occasioned by the contact of the cold mercury, is apt to break the
glass. In which case, the sudden fall of the column of mercury, which
happens the moment the least flaw is produced in the glass, causes such
a wave, as throws a great part of the quicksilver from the bason. To
avoid this inconvenience, and to ensure success to the experiment, one
gross and a half of iron is sufficient to burn in a bell-glass, which
holds about eight pints of air. The glass ought likewise to be strong,
that it may be able to bear the weight of the column of mercury which it
has to support.
By this experiment, it is not possible to determine, at one time, both
the additional weight acquired by the iron, and the changes which have
taken place in the air. If it is wished to ascertain what additional
weight has been gained by the iron, and the proportion between that and
the air absorbed, we must carefully mark upon the bell-glass, with a
diamond, the height of the mercury, both before and after the
experiment[9]. After this, the syphon (GH, Pl. IV. fig. 3.) guarded, as
before, with a bit of paper, to prevent its filling with mercury, is to
be introduced under the bell-glass, having the thumb placed upon the
extremity, G, of the syphon, to regulate the passage of the air; and by
this means the air is gradually admitted, so as to let the mercury fall
to its level. This being done, the bell-glass is to be carefully
removed, the globules of melted iron contained in the cup, and those
which have been scattered about, and swim upon the mercury, are to be
accurately collected, and the whole is to be weighed. The iron will be
found in that state called _martial ethiops_ by the old chemists,
possessing a degree of metallic brilliancy, very friable, and readily
reducible into powder, under the hammer, or with a pestle and mortar. If
the experiment has succeeded well, from 100 grains of iron will be
obtained 135 or 136 grains of ethiops, which is an augmentation of 35
per cent.
If all the attention has been paid to this experiment which it deserves,
the air will be found diminished in weight exactly equal to what the
iron has gained. Having therefore burnt 100 grains of iron, which has
acquired an additional weight of 35 grains, the diminution of air will
be found exactly 70 cubical inches; and it will be found, in the sequel,
that the weight of vital air is pretty nearly half a grain for each
cubical inch; so that, in effect, the augmentation of weight in the one
exactly coincides with the loss of it in the other.
I shall observe here, once for all, that, in every experiment of this
kind, the pressure and temperature of the air, both before and after the
experiment, must be reduced, by calculation, to a common standard of 10
deg. (54.5 deg.) of the thermometer, and 28 inches of the barometer.
Towards the end of this work, the manner of performing this very
necessary reduction will be found accurately detailed.
If it be required to examine the nature of the air which remains after
this experiment, we must operate in a somewhat different manner. After
the combustion is finished, and the vessels have cooled, we first take
out the cup, and the burnt iron, by introducing the hand through the
quicksilver, under the bell-glass; we next introduce some solution of
potash, or caustic alkali, or of the sulphuret of potash, or such other
substance as is judged proper for examining their action upon the
residuum of air. I shall, in the sequel, give an account of these
methods of analysing air, when I have explained the nature of these
different substances, which are only here in a manner accidentally
mentioned. After this examination, so much water must be let into the
glass as will displace the quicksilver, and then, by means of a shallow
dish placed below the bell-glass, it is to be removed into the common
water pneumato-chemical apparatus, where the air remaining may be
examined at large, and with great facility.
When very soft and very pure iron has been employed in this experiment,
and, if the combustion has been performed in the purest respirable or
vital air, free from all admixture of the noxious or mephitic part, the
air which remains after the combustion will be found as pure as it was
before; but it is difficult to find iron entirely free from a small
portion of charry matter, which is chiefly abundant in steel. It is
likewise exceedingly difficult to procure the pure air perfectly free
from some admixture of mephitis, with which it is almost always
contaminated; but this species of noxious air does not, in the smallest
degree, disturb the result of the experiment, as it is always found at
the end exactly in the same proportion as at the beginning.
I mentioned before, that we have two ways of determining the constituent
parts of atmospheric air, the method of analysis, and that by synthesis.
The calcination of mercury has furnished us with an example of each of
these methods, since, after having robbed the respirable part of its
base, by means of the mercury, we have restored it, so as to recompose
an air precisely similar to that of the atmosphere. But we can equally
accomplish this synthetic composition of atmospheric air, by borrowing
the materials of which it is composed from different kingdoms of nature.
We shall see hereafter that, when animal substances are dissolved in the
nitric acid, a great quantity of gas is disengaged, which extinguishes
light, and is unfit for animal respiration, being exactly similar to the
noxious or mephitic part of atmospheric air. And, if we take 73 parts,
by weight, of this elastic fluid, and mix it with 27 parts of highly
respirable air, procured from calcined mercury, we will form an elastic
fluid precisely similar to atmospheric air in all its properties.
There are many other methods of separating the respirable from the
noxious part of the atmospheric air, which cannot be taken notice of in
this part, without anticipating information, which properly belongs to
the subsequent chapters. The experiments already adduced may suffice for
an elementary treatise; and, in matters of this nature, the choice of
our evidences is of far greater consequence than their number.
I shall close this article, by pointing out the property which
atmospheric air, and all the known gasses, possess of dissolving water,
which is of great consequence to be attended to in all experiments of
this nature. Mr Saussure found, by experiment, that a cubical foot of
atmospheric air is capable of holding 12 grains of water in solution:
Other gasses, as the carbonic acid, appear capable of dissolving a
greater quantity; but experiments are still wanting by which to
determine their several proportions. This water, held in solution by
gasses, gives rise to particular phenomena in many experiments, which
require great attention, and which has frequently proved the source of
great errors to chemists in determining the results of their
experiments.
FOOTNOTES:
[9] It will likewise be necessary to take care that the air contained in
the glass, both before and after the experiment, be reduced to a common
temperature and pressure, otherwise the results of the following
calculations will be fallacious.--E.
CHAP. IV.
_Nomenclature of the several Constituent Parts of Atmospheric Air._
Hitherto I have been obliged to make use of circumlocution, to express
the nature of the several substances which constitute our atmosphere,
having provisionally used the terms of _respirable_ and _noxious_, or
_non-respirable parts of the air_. But the investigations I mean to
undertake require a more direct mode of expression; and, having now
endeavoured to give simple and distinct ideas of the different
substances which enter into the composition of the atmosphere, I shall
henceforth express these ideas by words equally simple.
The temperature of our earth being very near to that at which water
becomes solid, and reciprocally changes from solid to fluid, and as this
phenomenon takes place frequently under our observation, it has very
naturally followed, that, in the languages of at least every climate
subjected to any degree of winter, a term has been used for signifying
water in the state of solidity, when deprived of its caloric. The same,
however, has not been found necessary with respect to water reduced to
the state of vapour by an additional dose of caloric; since those
persons who do not make a particular study of objects of this kind, are
still ignorant that water, when in a temperature only a little above the
boiling heat, is changed into an elastic aeriform fluid, susceptible,
like all other gasses, of being received and contained in vessels, and
preserving its gasseous form so long as it remains at the temperature of
80 deg. (212 deg.), and under a pressure not exceeding 28 inches of the
mercurial barometer. As this phenomenon has not been generally observed,
no language has used a particular term for expressing water in this
state[10]; and the same thing occurs with all fluids, and all
substances, which do not evaporate in the common temperature, and under
the usual pressure of our atmosphere.
For similar reasons, names have not been given to the liquid or concrete
states of most of the aeriform fluids: These were not known to arise
from the combination of caloric with certain bases; and, as they had not
been seen either in the liquid or solid states, their existence, under
these forms, was even unknown to natural philosophers.
We have not pretended to make any alteration upon such terms as are
sanctified by ancient custom; and, therefore, continue to use the words
_water_ and _ice_ in their common acceptation: We likewise retain the
word _air_, to express that collection of elastic fluids which composes
our atmosphere; but we have not thought it necessary to preserve the
same respect for modern terms, adopted by latter philosophers, having
considered ourselves as at liberty to reject such as appeared liable to
occasion erroneous ideas of the substances they are meant to express,
and either to substitute new terms, or to employ the old ones, after
modifying them in such a manner as to convey more determinate ideas. New
words have been drawn, chiefly from the Greek language, in such a manner
as to make their etymology convey some idea of what was meant to be
represented; and these we have always endeavoured to make short, and of
such a nature as to be changeable into adjectives and verbs.
Following these principles, we have, after Mr Macquer's example,
retained the term _gas_, employed by Vanhelmont, having arranged the
numerous class of elastic aeriform fluids under that name, excepting
only atmospheric air. _Gas_, therefore, in our nomenclature, becomes a
generic term, expressing the fullest degree of saturation in any body
with caloric; being, in fact, a term expressive of a mode of existence.
To distinguish each species of gas, we employ a second term from the
name of the base, which, saturated with caloric, forms each particular
gas. Thus, we name water combined to saturation with caloric, so as to
form an elastic fluid, _aqueous gas_; ether, combined in the same
manner, _etherial gas_; the combination of alkohol with caloric, becomes
_alkoholic gas_; and, following the same principles, we have _muriatic
acid gas_, _ammoniacal gas_, and so on of every substance susceptible of
being combined with caloric, in such a manner as to assume the gasseous
or elastic aeriform state.
We have already seen, that the atmospheric air is composed of two
gasses, or aeriform fluids, one of which is capable, by respiration, of
contributing to animal life, and in which metals are calcinable, and
combustible bodies may burn; the other, on the contrary, is endowed with
directly opposite qualities; it cannot be breathed by animals, neither
will it admit of the combustion of inflammable bodies, nor of the
calcination of metals. We have given to the base of the former, or
respirable portion of the air, the name of _oxygen_, from [Greek: oxys]
_acidum_, and [Greek: geinomas], _gignor_; because, in reality, one of
the most general properties of this base is to form acids, by combining
with many different substances. The union of this base with caloric we
term _oxygen gas_, which is the same with what was formerly called
_pure_, or _vital air_. The weight of this gas, at the temperature of
10 deg. (54.50), and under a pressure equal to 28 inches of the barometer,
is half a grain for each cubical inch, or one ounce and a half to each
cubical foot.
The chemical properties of the noxious portion of atmospheric air being
hitherto but little known, we have been satisfied to derive the name of
its base from its known quality of killing such animals as are forced to
breathe it, giving it the name of _azote_, from the Greek privitive
particle [Greek: a] and [Greek: xae], vita; hence the name of the
noxious part of atmospheric air is _azotic gas_; the weight of which, in
the same temperature, and under the same pressure, is 1 oz. 2 gros
and 48 grs. to the cubical foot, or 0.4444 of a grain to the cubical
inch. We cannot deny that this name appears somewhat extraordinary; but
this must be the case with all new terms, which cannot be expected to
become familiar until they have been some time in use. We long
endeavoured to find a more proper designation without success; it was at
first proposed to call it _alkaligen gas_, as, from the experiments of
Mr Berthollet, it appears to enter into the composition of ammoniac, or
volatile alkali; but then, we have as yet no proof of its making one of
the constituent elements of the other alkalies; beside, it is proved to
compose a part of the nitric acid, which gives as good reason to have
called it _nitrigen_. For these reasons, finding it necessary to reject
any name upon systematic principles, we have considered that we run no
risk of mistake in adopting the terms of _azote_, and _azotic gas_,
which only express a matter of fact, or that property which it
possesses, of depriving such animals as breathe it of their lives.
I should anticipate subjects more properly reserved for the subsequent
chapters, were I in this place to enter upon the nomenclature of the
several species of gasses: It is sufficient, in this part of the work,
to establish the principles upon which their denominations are founded.
The principal merit of the nomenclature we have adopted is, that, when
once the simple elementary substance is distinguished by an appropriate
term, the names of all its compounds derive readily, and necessarily,
from this first denomination.
FOOTNOTES:
[10] In English, the word _steam_ is exclusively appropriated to water
in the state of vapour. E.
CHAP. V.
_Of the Decomposition of Oxygen Gas by Sulphur, Phosphorus, and
Charcoal--and of the Formation of Acids in general._
In performing experiments, it is a necessary principle, which ought
never to be deviated from, that they be simplified as much as possible,
and that every circumstance capable of rendering their results
complicated be carefully removed. Wherefore, in the experiments which
form the object of this chapter, we have never employed atmospheric air,
which is not a simple substance. It is true, that the azotic gas, which
forms a part of its mixture, appears to be merely passive during
combustion and calcination; but, besides that it retards these
operations very considerably, we are not certain but it may even alter
their results in some circumstances; for which reason, I have thought it
necessary to remove even this possible cause of doubt, by only making
use of pure oxygen gas in the following experiments, which show the
effects produced by combustion in that gas; and I shall advert to such
differences as take place in the results of these, when the oxygen gas,
or pure vital air, is mixed, in different proportions, with azotic gas.
Having filled a bell-glass (A. Pl. iv. fig. 3), of between five and six
pints measure, with oxygen gas, I removed it from the water trough,
where it was filled, into the quicksilver bath, by means of a shallow
glass dish slipped underneath, and having dried the mercury, I
introduced 61-1/4 grains of Kunkel's phosphorus in two little China
cups, like that represented at D, fig. 3. under the glass A; and that I
might set fire to each of the portions of phosphorus separately, and to
prevent the one from catching fire from the other, one of the dishes was
covered with a piece of flat glass. I next raised the quicksilver in the
bell-glass up to E F, by sucking out a sufficient portion of the gas by
means of the syphon G H I. After this, by means of the crooked iron wire
(fig. 16.), made red hot, I set fire to the two portions of phosphorus
successively, first burning that portion which was not covered with the
piece of glass. The combustion was extremely rapid, attended with a very
brilliant flame, and considerable disengagement of light and heat. In
consequence of the great heat induced, the gas was at first much
dilated, but soon after the mercury returned to its level, and a
considerable absorption of gas took place; at the same time, the whole
inside of the glass became covered with white light flakes of concrete
phosphoric acid.
At the beginning of the experiment, the quantity of oxygen gas, reduced,
as above directed, to a common standard, amounted to 162 cubical inches;
and, after the combustion was finished, only 23-1/4 cubical inches,
likewise reduced to the standard, remained; so that the quantity of
oxygen gas absorbed during the combustion was 138-3/4 cubical inches,
equal to 69.375 grains.
A part of the phosphorus remained unconsumed in the bottom of the cups,
which being washed on purpose to separate the acid, weighed about 16-1/4
grains; so that about 45 grains of phosphorus had been burned: But, as
it is hardly possible to avoid an error of one or two grains, I leave
the quantity so far qualified. Hence, as nearly 45 grains of phosphorus
had, in this experiment, united with 69.375 grains of oxygen, and as no
gravitating matter could have escaped through the glass, we have a right
to conclude, that the weight of the substance resulting from the
combustion in form of white flakes, must equal that of the phosphorus
and oxygen employed, which amounts to 114.375 grains. And we shall
presently find, that these flakes consisted entirely of a solid or
concrete acid. When we reduce these weights to hundredth parts, it will
be found, that 100 parts of phosphorus require 154 parts of oxygen for
saturation, and that this combination will produce 254 parts of concrete
phosphoric acid, in form of white fleecy flakes.
This experiment proves, in the most convincing manner, that, at a
certain degree of temperature, oxygen possesses a stronger elective
attraction, or affinity, for phosphorus than for caloric; that, in
consequence of this, the phosphorus attracts the base of oxygen gas from
the caloric, which, being set free, spreads itself over the surrounding
bodies. But, though this experiment be so far perfectly conclusive, it
is not sufficiently rigorous, as, in the apparatus described, it is
impossible to ascertain the weight of the flakes of concrete acid which
are formed; we can therefore only determine this by calculating the
weights of oxygen and phosphorus employed; but as, in physics, and in
chemistry, it is not allowable to suppose what is capable of being
ascertained by direct experiment, I thought it necessary to rep at this
experiment, as follows, upon a larger scale, and by means of a different
apparatus.
I took a large glass baloon (A. Pl. iv. fig. 4.) with an opening three
inches diameter, to which was fitted a crystal stopper ground with
emery, and pierced with two holes for the tubes yyy, xxx. Before
shutting the baloon with its stopper, I introduced the support BC,
surmounted by the china cup D, containing 150 grs. of phosphorus; the
stopper was then fitted to the opening of the baloon, luted with fat
lute, and covered with slips of linen spread with quick-lime and white
of eggs: When the lute was perfectly dry, the weight of the whole
apparatus was determined to within a grain, or a grain and a half. I
next exhausted the baloon, by means of an air pump applied to the tube
XXX, and then introduced oxygen gas by means of the tube yyy, having a
stop cock adapted to it. This kind of experiment is most readily and
most exactly performed by means of the hydro-pneumatic machine described
by Mr Meusnier and me in the Memoirs of the Academy for 1782, pag. 466.
and explained in the latter part of this work, with several important
additions and corrections since made to it by Mr Meusnier. With this
instrument we can readily ascertain, in the most exact manner, both the
quantity of oxygen gas introduced into the baloon, and the quantity
consumed during the course of the experiment.
When all things were properly disposed, I set fire to the phosphorus
with a burning glass. The combustion was extremely rapid, accompanied
with a bright flame, and much heat; as the operation went on, large
quantities of white flakes attached themselves to the inner surface of
the baloon, so that at last it was rendered quite opake. The quantity
of these flakes at last became so abundant, that, although fresh oxygen
gas was continually supplied, which ought to have supported the
combustion, yet the phosphorus was soon extinguished. Having allowed the
apparatus to cool completely, I first ascertained the quantity of oxygen
gas employed, and weighed the baloon accurately, before it was opened. I
next washed, dried, and weighed the small quantity of phosphorus
remaining in the cup, on purpose to determine the whole quantity of
phosphorus consumed in the experiment; this residuum of the phosphorus
was of a yellow ochrey colour. It is evident, that by these several
precautions, I could easily determine, 1st, the weight of the phosphorus
consumed; 2d, the weight of the flakes produced by the combustion; and,
3d, the weight of the oxygen which had combined with the phosphorus.
This experiment gave very nearly the same results with the former, as it
proved that the phosphorus, during its combustion, had absorbed a little
more than one and a half its weight of oxygen; and I learned with more
certainty, that the weight of the new substance, produced in the
experiment, exactly equalled the sum of the weights of the phosphorus
consumed, and oxygen absorbed, which indeed was easily determinable _a
priori_. If the oxygen gas employed be pure, the residuum after
combustion is as pure as the gas employed; this proves that nothing
escapes from the phosphorus, capable of altering the purity of the
oxygen gas, and that the only action of the phosphorus is to separate
the oxygen from the caloric, with which it was before united.
I mentioned above, that when any combustible body is burnt in a hollow
sphere of ice, or in an apparatus properly constructed upon that
principle, the quantity of ice melted during the combustion is an exact
measure of the quantity of caloric disengaged. Upon this head, the
memoir given by M. de la Place and me, A(masculine ordinal). 1780, p. 355,
may be consulted. Having submitted the combustion of phosphorus to this
trial, we found that one pound of phosphorus melted a little more than
100 pounds of ice during its combustion.
The combustion of phosphorus succeeds equally well in atmospheric air as
in oxygen gas, with this difference, that the combustion is vastly
slower, being retarded by the large proportion of azotic gas mixed with
the oxygen gas, and that only about one-fifth part of the air employed
is absorbed, because as the oxygen gas only is absorbed, the proportion
of the azotic gas becomes so great toward the close of the experiment,
as to put an end to the combustion.
I have already shown, that phosphorus is changed by combustion into an
extremely light, white, flakey matter; and its properties are entirely
altered by this transformation: From being insoluble in water, it
becomes not only soluble, but so greedy of moisture, as to attract the
humidity of the air with astonishing rapidity; by this means it is
converted into a liquid, considerably more dense, and of more specific
gravity than water. In the state of phosphorus before combustion, it had
scarcely any sensible taste, by its union with oxygen it acquires an
extremely sharp and sour taste: in a word, from one of the class of
combustible bodies, it is changed into an incombustible substance, and
becomes one of those bodies called acids.
This property of a combustible substance to be converted into an acid,
by the addition of oxygen, we shall presently find belongs to a great
number of bodies: Wherefore, strict logic requires that we should adopt
a common term for indicating all these operations which produce
analogous results; this is the true way to simplify the study of
science, as it would be quite impossible to bear all its specifical
details in the memory, if they were not classically arranged. For this
reason, we shall distinguish this conversion of phosphorus into an acid,
by its union with oxygen, and in general every combination of oxygen
with a combustible substance, by the term of _oxygenation_: from which
I shall adopt the verb to _oxygenate_, and of consequence shall say,
that in _oxygenating_ phosphorus we convert it into an acid.
Sulphur is likewise a combustible body, or, in other words, it is a body
which possesses the power of decomposing oxygen gas, by attracting the
oxygen from the caloric with which it was combined. This can very easily
be proved, by means of experiments quite similar to those we have given
with phosphorus; but it is necessary to premise, that in these
operations with sulphur, the same accuracy of result is not to be
expected as with phosphorus; because the acid which is formed by the
combustion of sulphur is difficultly condensible, and because sulphur
burns with more difficulty, and is soluble in the different gasses. But
I can safely assert, from my own experiments, that sulphur in burning
absorbs oxygen gas; that the resulting acid is considerably heavier than
the sulphur burnt; that its weight is equal to the sum of the weights of
the sulphur which has been burnt, and of the oxygen absorbed; and,
lastly that this acid is weighty, incombustible, and miscible with water
in all proportions: The only uncertainty remaining upon this head, is
with regard to the proportions of sulphur and of oxygen which enter into
the composition of the acid.
Charcoal, which, from all our present knowledge regarding it, must be
considered as a simple combustible body, has likewise the property of
decomposing oxygen gas, by absorbing its base from the caloric: But the
acid resulting from this combustion does not condense in the common
temperature; under the pressure of our atmosphere, it remains in the
state of gas, and requires a large proportion of water to combine with
or be dissolved in. This acid has, however, all the known properties of
other acids, though in a weaker degree, and combines, like them, with
all the bases which are susceptible of forming neutral salts.
The combustion of charcoal in oxygen gas, may be effected like that of
phosphorus in the bell-glass, (A. Pl. IV. fig. 3.) placed over mercury:
but, as the heat of red hot iron is not sufficient to set fire to the
charcoal, we must add a small morsel of tinder, with a minute particle
of phosphorus, in the same manner as directed in the experiment for the
combustion of iron. A detailed account of this experiment will be found
in the memoirs of the academy for 1781, p. 448. By that experiment it
appears, that 28 parts by weight of charcoal require 72 parts of oxygen
for saturation, and that the aeriform acid produced is precisely equal
in weight to the sum of the weights of the charcoal and oxygen gas
employed. This aeriform acid was called fixed or fixable air by the
chemists who first discovered it; they did not then know whether it was
air resembling that of the atmosphere, or some other elastic fluid,
vitiated and corrupted by combustion; but since it is now ascertained to
be an acid, formed like all others by the oxygenation of its peculiar
base, it is obvious that the name of fixed air is quite ineligible[11].
By burning charcoal in the apparatus mentioned p. 60, Mr de la Place and
I found that one lib. of charcoal melted 96 libs. 6 oz. of ice;
that, during the combustion, 2 libs. 9 oz. 1 gros. 10 grs. of
oxygen were absorbed, and that 3 libs. 9 oz. 1 gros. 10 grs. of
acid gas were formed. This gas weighs 0.695 parts of a grain for each
cubical inch, in the common standard temperature and pressure mentioned
above, so that 34,242 cubical inches of acid gas are produced by the
combustion of one pound of charcoal.
I might multiply these experiments, and show by a numerous succession of
facts, that all acids are formed by the combustion of certain
substances; but I am prevented from doing so in place, by the plan
which I have laid down, of proceeding only from facts already
ascertained, to such as are unknown, and of drawing my examples only
from circumstances already explained. In the mean time, however, the
three examples above cited may suffice for giving a clear and accurate
conception of the manner in which acids are formed. By these it may be
clearly seen, that oxygen is an element common to them all, which
constitutes their acidity; and that they differ from each other,
according to the nature of the oxygenated or acidified substance. We
must therefore, in every acid, carefully distinguish between the
acidifiable, base, which Mr de Morveau calls the radical, and the
acidifiing principle or oxygen.
FOOTNOTES:
[11] It may be proper to remark, though here omitted by the author,
that, in conformity with the general principles of the new nomenclature,
this acid is by Mr Lavoisier and his coleagues called the carbonic acid,
and when in the aeriform state carbonic acid gas. E.
CHAP. VI.
_Of the Nomenclature of Acids in general, and particularly of those
drawn from Nitre and Sea-Salt._
It becomes extremely easy, from the principles laid down in the
preceding chapter, to establish a systematic nomenclature for the acids:
The word _acid_, being used as a generic term, each acid falls to be
distinguished in language, as in nature, by the name of its base or
radical. Thus, we give the generic name of acids to the products of the
combustion or oxygenation of phosphorus, of sulphur, and of charcoal;
and these products are respectively named, the _phosphoric acid_, the
_sulphuric acid_, and the _carbonic acid_.
There is however, a remarkable circumstance in the oxygenation of
combustible bodies, and of a part of such bodies as are convertible into
acids, that they are susceptible of different degrees of saturation with
oxygen, and that the resulting acids, though formed by the union of the
same elements, are possessed of different properties, depending upon
that difference of proportion. Of this, the phosphoric acid, and more
especially the sulphuric, furnishes us with examples. When sulphur is
combined with a small proportion of oxygen, it forms, in this first or
lower degree of oxygenation, a volatile acid, having a penetrating
odour, and possessed of very particular qualities. By a larger
proportion of oxygen, it is changed into a fixed, heavy acid, without
any odour, and which, by combination with other bodies, gives products
quite different from those furnished by the former. In this instance,
the principles of our nomenclature seem to fail; and it seems difficult
to derive such terms from the name of the acidifiable base, as shall
distinctly express these two degrees of saturation, or oxygenation,
without circumlocution. By reflection, however, upon the subject, or
perhaps rather from the necessity of the case, we have thought it
allowable to express these varieties in the oxygenation of the acids, by
simply varying the termination of their specific names. The volatile
acid produced from sulphur was anciently known to Stahl under the name
of _sulphurous_ acid[12]. We have preserved that term for this acid
from sulphur under-saturated with oxygen; and distinguish the other, or
completely saturated or oxygenated acid, by the name of _sulphuric_
acid. We shall therefore say, in this new chemical language, that
sulphur, in combining with oxygen, is susceptible of two degrees of
saturation; that the first, or lesser degree, constitutes sulphurous
acid, which is volatile and penetrating; whilst the second, or higher
degree of saturation, produces sulphuric acid, which is fixed and
inodorous. We shall adopt this difference of termination for all the
acids which assume several degrees of saturation. Hence we have a
phosphorous and a phosphoric acid, an acetous and an acetic acid; and so
on, for others in similar circumstances.
This part of chemical science would have been extremely simple, and the
nomenclature of the acids would not have been at all perplexed, as it is
now in the old nomenclature, if the base or radical of each acid had
been known when the acid itself was discovered. Thus, for instance,
phosphorus being a known substance before the discovery of its acid,
this latter was rightly distinguished by a term drawn from the name of
its acidifiable base. But when, on the contrary, an acid happened to be
discovered before its base, or rather, when the acidifiable base from
which it was formed remained unknown, names were adopted for the two,
which have not the smallest connection; and thus, not only the memory
became burthened with useless appellations, but even the minds of
students, nay even of experienced chemists, became filled with false
ideas, which time and reflection alone is capable of eradicating. We may
give an instance of this confusion with respect to the acid sulphur: The
former chemists having procured this acid from the vitriol of iron, gave
it the name of the vitriolic acid from the name of the substance which
produced it; and they were then ignorant that the acid procured from
sulphur by combustion was exactly the same.
The same thing happened with the aeriform acid formerly called _fixed
air_; it not being known that this acid was the result of combining
charcoal with oxygen, a variety of denominations have been given to it,
not one of which conveys just ideas of its nature or origin. We have
found it extremely easy to correct and modify the ancient language with
respect to these acids proceeding from known bases, having converted the
name of _vitriolic acid_ into that of _sulphuric_, and the name of
_fixed air_ into that of _carbonic acid_; but it is impossible to follow
this plan with the acids whose bases are still unknown; with these we
have been obliged to use a contrary plan, and, instead of forming the
name of the acid from that of its base, have been forced to denominate
the unknown base from the name of the known acid, as happens in the case
of the acid which is procured from sea salt.
To disengage this acid from the alkaline base with which it is combined,
we have only to pour sulphuric acid upon sea-salt, immediately a brisk
effervescence takes place, white vapours arise, of a very penetrating
odour, and, by only gently heating the mixture, all the acid is driven
off. As, in the common temperature and pressure of our atmosphere, this
acid is naturally in the state of gas, we must use particular
precautions for retaining it in proper vessels. For small experiments,
the most simple and most commodious apparatus consists of a small retort
G, (Pl. V. Fig. 5.), into which the sea-salt is introduced, well
dried[13], we then pour on some concentrated sulphuric acid, and
immediately introduce the beak of the retort under little jars or
bell-glasses A, (same Plate and Fig.), previously filled with
quicksilver. In proportion as the acid gas is disengaged, it passes into
the jar, and gets to the top of the quicksilver, which it displaces.
When the disengagement of the gas slackens, a gentle heat is applied to
the retort, and gradually increased till nothing more passes over. This
acid gas has a very strong affinity with water, which absorbs an
enormous quantity of it, as is proved by introducing a very thin layer
of water into the glass which contains the gas; for, in an instant, the
whole acid gas disappears, and combines with the water.
This latter circumstance is taken advantage of in laboratories and
manufactures, on purpose to obtain the acid of sea-salt in a liquid
form; and for this purpose the apparatus (Pl. IV. Fig. 1.) is employed.
It consists, 1st, of a tubulated retort A, into which the sea-salt, and
after it the sulphuric acid, are introduced through the opening H; 2d,
of the baloon or recipient c, b, intended for containing the small
quantity of liquid which passes over during the process; and, 3d, of a
set of bottles, with two mouths, L, L, L, L, half filled with water,
intended for absorbing the gas disengaged by the distillation. This
apparatus will be more amply described in the latter part of this work.
Although we have not yet been able, either to compose or to decompound
this acid of sea-salt, we cannot have the smallest doubt that it, like
all other acids, is composed by the union of oxygen with an acidifiable
base. We have therefore called this unknown substance the _muriatic
base_, or _muriatic radical_, deriving this name, after the example of
Mr Bergman and Mr de Morveau, from the Latin word _muria_, which was
anciently used to signify sea-salt. Thus, without being able exactly to
determine the component parts of _muriatic acid_, we design, by that
term, a volatile acid, which retains the form of gas in the common
temperature and pressure of our atmosphere, which combines with great
facility, and in great quantity, with water, and whose acidifiable base
adheres so very intimately with oxygen, that no method has hitherto been
devised for separating them. If ever this acidifiable base of the
muriatic acid is discovered to be a known substance, though now unknown
in that capacity, it will be requisite to change its present
denomination for one analogous with that of its base.
In common with sulphuric acid, and several other acids, the muriatic is
capable of different degrees of oxygenation; but the excess of oxygen
produces quite contrary effects upon it from what the same circumstance
produces upon the acid of sulphur. The lower degree of oxygenation
converts sulphur into a volatile gasseous acid, which only mixes in
small proportions with water, whilst a higher oxygenation forms an acid
possessing much stronger acid properties, which is very fixed and cannot
remain in the state of gas but in a very high temperature, which has no
smell, and which mixes in large proportion with water. With muriatic
acid, the direct reverse takes place; an additional saturation with
oxygen renders it more volatile, of a more penetrating odour, less
miscible with water, and diminishes its acid properties. We were at
first inclined to have denominated these two degrees of saturation in
the same manner as we had done with the acid of sulphur, calling the
less oxygenated _muriatous acid_, and that which is more saturated with
oxygen _muriatic acid_: But, as this latter gives very particular
results in its combinations, and as nothing analogous to it is yet known
in chemistry, we have left the name of muriatic acid to the less
saturated, and give the latter the more compounded appellation of
_oxygenated muriatic acid_.
Although the base or radical of the acid which is extracted from nitre
or saltpetre be better known, we have judged proper only to modify its
name in the same manner with that of the muriatic acid. It is drawn from
nitre, by the intervention of sulphuric acid, by a process similar to
that described for extracting the muriatic acid, and by means of the
same apparatus (Pl. IV. Fig. 1.). In proportion as the acid passes over,
it is in part condensed in the baloon or recipient, and the rest is
absorbed by the water contained in the bottles L,L,L,L; the water
becomes first green, then blue, and at last yellow, in proportion to
the concentration of the acid. During this operation, a large quantity
of oxygen gas, mixed with a small proportion of azotic gas, is
disengaged.
This acid, like all others, is composed of oxygen, united to an
acidifiable base, and is even the first acid in which the existence of
oxygen was well ascertained. Its two constituent elements are but weakly
united, and are easily separated, by presenting any substance with which
oxygen has a stronger affinity than with the acidifiable base peculiar
to this acid. By some experiments of this kind, it was first discovered
that azote, or the base of mephitis or azotic gas, constituted its
acidifiable base or radical; and consequently that the acid of nitre was
really an azotic acid, having azote for its base, combined with oxygen.
For these reasons, that we might be consistent with our principles, it
appeared necessary, either to call the acid by the name of _azotic_, or
to name the base _nitric radical_; but from either of these we were
dissuaded, by the following considerations. In the _first_ place, it
seemed difficult to change the name of nitre or saltpetre, which has
been universally adopted in society, in manufactures, and in chemistry;
and, on the other hand, azote having been discovered by Mr Berthollet to
be the base of volatile alkali, or ammoniac, as well as of this acid,
we thought it improper to call it nitric radical. We have therefore
continued the term of azote to the base of that part of atmospheric air
which is likewise the nitric and ammoniacal radical; and we have named
the acid of nitre, in its lower and higher degrees of oxygenation,
_nitrous acid_ in the former, and _nitric acid_ in the latter state;
thus preserving its former appellation properly modified.
Several very respectable chemists have disapproved of this deference for
the old terms, and wished us to have persevered in perfecting a new
chemical language, without paying any respect for ancient usage; so
that, by thus steering a kind of middle course, we have exposed
ourselves to the censures of one sect of chemists, and to the
expostulations of the opposite party.
The acid of nitre is susceptible of assuming a great number of separate
states, depending upon its degree of oxygenation, or upon the
proportions in which azote and oxygen enter into its composition. By a
first or lowest degree of oxygenation, it forms a particular species of
gas, which we shall continue to name _nitrous gas_; this is composed
nearly of two parts, by weight, of oxygen combined with one part of
azote; and in this state it is not miscible with water. In this gas, the
azote is by no means saturated with oxygen, but, on the contrary, has
still a very great affinity for that element, and even attracts it from
atmospheric air, immediately upon getting into contact with it. This
combination of nitrous gas with atmospheric air has even become one of
the methods for determining the quantity of oxygen contained in air, and
consequently for ascertaining its degree of salubrity.
This addition of oxygen converts the nitrous gas into a powerful acid,
which has a strong affinity with water, and which is itself susceptible
of various additional degrees of oxygenation. When the proportions of
oxygen and azote is below three parts, by weight, of the former, to one
of the latter, the acid is red coloured, and emits copious fumes. In
this state, by the application of a gentle heat, it gives out nitrous
gas; and we term it, in this degree of oxygenation, _nitrous acid_. When
four parts, by weight, of oxygen, are combined with one part of azote,
the acid is clear and colourless, more fixed in the fire than the
nitrous acid, has less odour, and its constituent elements are more
firmly united. This species of acid, in conformity with our principles
of nomenclature, is called _nitric acid_.
Thus, nitric acid is the acid of nitre, surcharged with oxygen; nitrous
acid is the acid of nitre surcharged with azote; or, what is the same
thing, with nitrous gas; and this latter is azote not sufficiently
saturated with oxygen to possess the properties of an acid. To this
degree of oxygenation, we have afterwards, in the course of this work,
given the generical name of _oxyd_[14].
FOOTNOTES:
[12] The term formerly used by the English chemists for this acid was
written _sulphureous_; but we have thought proper to spell it as above,
that it may better conform with the similar terminations of nitrous,
carbonous, &c. to be used hereafter. In general, we have used the
English terminations _ic_ and _ous_ to translate the terms of the Author
which end with _ique_ and _cux_, with hardly any other alterations.--E.
[13] For this purpose, the operation called _decrepitation_ is used,
which consists in subjecting it to nearly a red heat, in a proper
vessel, so as to evaporate all its water of crystallization.--E.
[14] In strict conformity with the principles of the new nomenclature,
but which the Author has given his reasons for deviating from in this
instance, the following ought to have been the terms for azote, in its
several degrees of oxygenation: Azote, azotic gas, (azote combined with
caloric), azotic oxyd gas, nitrous acid, and nitric acid.--E.
CHAP. VII.
_Of the Decomposition of Oxygen Gas by means of Metals, and the
Formation of Metallic Oxyds._
Oxygen has a stronger affinity with metals heated to a certain degree
than with caloric; in consequence of which, all metallic bodies,
excepting gold, silver, and platina, have the property of decomposing
oxygen gas, by attracting its base from the caloric with which it was
combined. We have already shown in what manner this decomposition takes
place, by means of mercury and iron; having observed, that, in the case
of the first, it must be considered as a kind of gradual combustion,
whilst, in the latter, the combustion is extremely rapid, and attended
with a brilliant flame. The use of the heat employed in these operations
is to separate the particles of the metal from each other, and to
diminish their attraction of cohesion or aggregation, or, what is the
same thing, their mutual attraction for each other.
The absolute weight of metallic substances is augmented in proportion to
the quantity of oxygen they absorb; they, at the same time, lose their
metallic splendour, and are reduced into an earthy pulverulent matter.
In this state metals must not be considered as entirely saturated with
oxygen, because their action upon this element is counterbalanced by the
power of affinity between it and caloric. During the calcination of
metals, the oxygen is therefore acted upon by two separate and opposite
powers, that of its attraction for caloric, and that exerted by the
metal, and only tends to unite with the latter in consequence of the
excess of the latter over the former, which is, in general, very
inconsiderable. Wherefore, when metallic substances are oxygenated in
atmospheric air, or in oxygen gas, they are not converted into acids
like sulphur, phosphorus, and charcoal, but are only changed into
intermediate substances, which, though approaching to the nature of
salts, have not acquired all the saline properties. The old chemists
have affixed the name of _calx_ not only to metals in this state, but to
every body which has been long exposed to the action of fire without
being melted. They have converted this word _calx_ into a generical
term, under which they confound calcareous earth, which, from a neutral
salt, which it really was before calcination, has been changed by fire
into an earthy alkali, by _losing_ half of its weight, with metals
which, by the same means, have joined themselves to a new substance,
whose quantity often _exceeds_ half their weight, and by which they
have been changed almost into the nature of acids. This mode of
classifying substances of so very opposite natures, under the same
generic name, would have been quite contrary to our principles of
nomenclature, especially as, by retaining the above term for this state
of metallic substances, we must have conveyed very false ideas of its
nature. We have, therefore, laid aside the expression _metallic calx_
altogether, and have substituted in its place the term _oxyd_, from the
Greek word [Greek: oxys].
By this may be seen, that the language we have adopted is both copious
and expressive. The first or lowest degree of oxygenation in bodies,
converts them into _oxyds_; a second degree of additional oxygenation
constitutes the class of acids, of which the specific names, drawn from
their particular bases, terminate in _ous_, as the _nitrous_ and
_sulphurous_ acids; the third degree of oxygenation changes these into
the species of acids distinguished by the termination in ic, as the
_nitric_ and _sulphuric_ acids; and, lastly, we can express a fourth, or
highest degree of oxygenation, by adding the word _oxygenated_ to the
name of the acid, as has been already done with the _oxygenated
muriatic_ acid.
We have not confined the term _oxyd_ to expressing the combinations of
metals with oxygen, but have extended it to signify that first degree of
oxygenation in all bodies, which, without converting them into acids,
causes them to approach to the nature of salts. Thus, we give the name
of _oxyd of sulphur_ to that soft substance into which sulphur is
converted by incipient combustion; and we call the yellow matter left by
phosphorus, after combustion, by the name of _oxyd of phosphorus_. In
the same manner, nitrous gas, which is azote in its first degree of
oxygenation, is the _oxyd of azote_. We have likewise oxyds in great
numbers from the vegetable and animal kingdoms; and I shall show, in the
sequel, that this new language throws great light upon all the
operations of art and nature.
We have already observed, that almost all the metallic oxyds have
peculiar and permanent colours. These vary not only in the different
species of metals, but even according to the various degrees of
oxygenation in the same metal. Hence we are under the necessity of
adding two epithets to each oxyd, one of which indicates the metal
_oxydated_[15], while the other indicates the peculiar colour of the
oxyd. Thus, we have the black oxyd of iron, the red oxyd of iron, and
the yellow oxyd of iron; which expressions respectively answer to the
old unmeaning terms of martial ethiops, colcothar, and rust of iron, or
ochre. We have likewise the gray, yellow, and red oxyds of lead, which
answer to the equally false or insignificant terms, ashes of lead,
massicot, and minium.
These denominations sometimes become rather long, especially when we
mean to indicate whether the metal has been oxydated in the air, by
detonation with nitre, or by means of acids; but then they always convey
just and accurate ideas of the corresponding object which we wish to
express by their use. All this will be rendered perfectly clear and
distinct by means of the tables which are added to this work.
FOOTNOTES:
[15] Here we see the word oxyd converted into the verb _to oxydate_,
_oxydated_, _oxydating_, after the same manner with the derivation of
the verb _to oxygenate_, _oxygenated_, _oxygenating_, from the word
_oxygen_. I am not clear of the absolute necessity of this second verb
here first introduced, but think, in a work of this nature, that it is
the duty of the translator to neglect every other consideration for the
sake of strict fidelity to the ideas of his author.--E.
CHAP. VIII.
_Of the Radical Principle of Water, and of its Decomposition by Charcoal
and Iron._
Until very lately, water has always been thought a simple substance,
insomuch that the older chemists considered it as an element. Such it
undoubtedly was to them, as they were unable to decompose it; or, at
least, since the decomposition which took place daily before their eyes
was entirely unnoticed. But we mean to prove, that water is by no means
a simple or elementary substance. I shall not here pretend to give the
history of this recent, and hitherto contested discovery, which is
detailed in the Memoirs of the Academy for 1781, but shall only bring
forwards the principal proofs of the decomposition and composition of
water; and, I may venture to say, that these will be convincing to such
as consider them impartially.
_Experiment First._
Having fixed the glass tube EF, (Pl. vii. fig. 11.) of from 8 to 12
lines diameter, across a furnace, with a small inclination from E to F,
lute the superior extremity E to the glass retort A, containing a
determinate quantity of distilled water, and to the inferior extremity
F, the worm SS fixed into the neck of the doubly tubulated bottle H,
which has the bent tube KK adapted to one of its openings, in such a
manner as to convey such aeriform fluids or gasses as may be disengaged,
during the experiment, into a proper apparatus for determining their
quantity and nature.
To render the success of this experiment certain, it is necessary that
the tube EF be made of well annealed and difficultly fusible glass, and
that it be coated with a lute composed of clay mixed with powdered
stone-ware; besides which, it must be supported about its middle by
means of an iron bar passed through the furnace, lest it should soften
and bend during the experiment. A tube of China-ware, or porcellain,
would answer better than one of glass for this experiment, were it not
difficult to procure one so entirely free from pores as to prevent the
passage of air or of vapours.
When things are thus arranged, a fire is lighted in the furnace EFCD,
which is supported of such a strength as to keep the tube EF red hot,
but not to make it melt; and, at the same time, such a fire is kept up
in the furnace VVXX, as to keep the water in the retort A continually
boiling.
In proportion as the water in the retort A is evaporated, it fills the
tube EF, and drives out the air it contained by the tube KK; the aqueous
gas formed by evaporation is condensed by cooling in the worm SS, and
falls, drop by drop, into the tubulated bottle H. Having continued this
operation until all the water be evaporated from the retort, and having
carefully emptied all the vessels employed, we find that a quantity of
water has passed over into the bottle H, exactly equal to what was
before contained in the retort A, without any disengagement of gas
whatsoever: So that this experiment turns out to be a simple
distillation; and the result would have been exactly the same, if the
water had been run from one vessel into the other, through the tube EF,
without having undergone the intermediate incandescence.
_Experiment Second._
The apparatus being disposed, as in the former experiment, 28 grs. of
charcoal, broken into moderately small parts, and which has previously
been exposed for a long time to a red heat in close vessels, are
introduced into the tube EF. Every thing else is managed as in the
preceding experiment.
The water contained in the retort A is distilled, as in the former
experiment, and, being condensed in the worm, falls into the bottle H;
but, at the same time, a considerable quantity of gas is disengaged,
which, escaping by the tube KK, is received in a convenient apparatus
for that purpose. After the operation is finished, we find nothing but a
few atoms of ashes remaining in the tube EF; the 28 grs. of charcoal
having entirely disappeared.
When the disengaged gasses are carefully examined, they are sound to
weigh 113.7 grs.[16]; these are of two kinds, viz. 144 cubical inches
of carbonic acid gas, weighing 100 grs. and 380 cubical inches of a
very light gas, weighing only 13.7 grs. which takes fire when in
contact with air, by the approach of a lighted body; and, when the water
which has passed over into the bottle H is carefully examined, it is
found to have lost 85.7 grs. of its weight. Thus, in this experiment,
85.7 grs. of water, joined to 28 grs. of charcoal, have combined in
such a way as to form 100 grs. of carbonic acid, and 13.7 grs. of a
particular gas capable of being burnt.
I have already shown, that 100 grs. of carbonic acid gas consists of
72 grs. of oxygen, combined with 28 grs. of charcoal; hence the 28
grs. of charcoal placed in the glass tube have acquired 72 grs. of
oxygen from the water; and it follows, that 85.7 grs. of water are
composed of 72 grs. of oxygen, combined with 13.7 grs. of a gas
susceptible of combustion. We shall see presently that this gas cannot
possibly have been disengaged from the charcoal, and must, consequently,
have been produced from the water.
I have suppressed some circumstances in the above account of this
experiment, which would only have complicated and obscured its results
in the minds of the reader. For instance, the inflammable gas dissolves
a very small part of the charcoal, by which means its weight is somewhat
augmented, and that of the carbonic gas proportionally diminished.
Altho' the alteration produced by this circumstance is very
inconsiderable; yet I have thought it necessary to determine its effects
by rigid calculation, and to report, as above, the results of the
experiment in its simplified state, as if this circumstance had not
happened. At any rate, should any doubts remain respecting the
consequences I have drawn from this experiment, they will be fully
dissipated by the following experiments, which I am going to adduce in
support of my opinion.
_Experiment Third._
The apparatus being disposed exactly as in the former experiment, with
this difference, that instead of the 28 grs. of charcoal, the tube EF
is filled with 274 grs. of soft iron in thin plates, rolled up
spirally. The tube is made red hot by means of its furnace, and the
water in the retort A is kept constantly boiling till it be all
evaporated, and has passed through the tube EF, so as to be condensed in
the bottle H.
No carbonic acid gas is disengaged in this experiment, instead of which
we obtain 416 cubical inches, or 15 grs. of inflammable gas, thirteen
times lighter than atmospheric air. By examining the water which has
been distilled, it is found to have lost 100 grs. and the 274 grs.
of iron confined in the tube are found to have acquired 85 grs.
additional weight, and its magnitude is considerably augmented. The iron
is now hardly at all attractable by the magnet; it dissolves in acids
without effervescence; and, in short, it is converted into a black oxyd,
precisely similar to that which has been burnt in oxygen gas.
In this experiment we have a true _oxydation_ of iron, by means of
water, exactly similar to that produced in air by the assistance of
heat. One hundred grains of water having been decomposed, 85 grs. of
oxygen have combined with the iron, so as to convert it into the state
of black oxyd, and 15 grs. of a peculiar inflammable gas are
disengaged: From all this it clearly follows, that water is composed of
oxygen combined with the base of an inflammable gas, in the respective
proportions of 85 parts, by weight of the former, to 15 parts of the
latter.
Thus water, besides the oxygen, which is one of its elements in common
with many other substances, contains another element as its constituent
base or radical, and for which we must find an appropriate term. None
that we could think of seemed better adapted than the word _hydrogen_,
which signifies the _generative principle of water_, from [Greek: ydor]
_aqua_, and [Greek: geinomas] _gignor_[17]. We call the combination of
this element with caloric _hydrogen gas_; and the term hydrogen
expresses the base of that gas, or the radical of water.
This experiment furnishes us with a new combustible body, or, in other
words, a body which has so much affinity with oxygen as to draw it from
its connection with caloric, and to decompose air or oxygen gas. This
combustible body has itself so great affinity with caloric, that, unless
when engaged in a combination with some other body, it always subsists
in the aeriform or gasseous state, in the usual temperature and pressure
of our atmosphere. In this state of gas it is about 1/13 of the weight
of an equal bulk of atmospheric air; it is not absorbed by water, though
it is capable of holding a small quantity of that fluid in solution, and
it is incapable of being used for respiration.