OF THE ATTEMPTS TO ESTABLISH A THEORY IN CHEMISTRY.
Bacon, Lord Verulam, as early as the commencement of the 17th century,
had pointed out the importance of chemical investigations, and had
predicted the immense advantages which would result from the science,
when it came to be properly cultivated and extended; but he did not
himself attempt either to construct a theory of chemistry, or even
to extend it beyond the bounds which it had reached before he began
to write. Neither did Boyle, notwithstanding the importance of his
investigations, and his comparative freedom from the prejudices of the
alchymists, attempt any thing like a theory of chemistry; though the
observations which he made in his Sceptical Chemist, had considerable
effect in overturning, or at least in hastening the downfall of the
absurd chemical opinions which at that time prevailed, and the puerile
hypotheses respecting the animal functions, and the pathology and
treatment of diseases founded on these opinions. The first person who
can with propriety be said to have attempted to construct a theory of
chemistry, was Beccher.
John Joachim Beccher, one of the most extraordinary men of the age in
which he lived, was born at Spires, in Germany, in the year 1635. His
father, as Beccher himself informs us, was a very learned Lutheran
preacher. As he lost his father when he was very young, and as that
part of Germany where he lived had been ruined by the thirty years’
war, his family was reduced to great poverty. However, his passion
for information was so great, that he contrived to educate himself by
studying what books he could procure, and in this way acquired a great
deal of knowledge. Afterwards he travelled through the greatest part of
Germany, Italy, Sweden, and Holland.
In the year 1666 he was appointed public professor of medicine in the
University of Mentz, and soon after chief physician to the elector.
In that capacity he took up his residence in Munich, where he was
furnished by the elector with an excellent laboratory: but he soon fell
into difficulties, the nature of which does not appear, and was obliged
to leave the place. He took refuge in Vienna, where, from his knowledge
of finance, he was appointed chamberlain to Count Zinzendorf, and
through him acquired so much importance in the eyes of the court, that
he was named a member of the newly-erected College of Commerce, and
obtained the title of imperial commercial counsellor and chamberlain.
But here also he speedily raised up so many enemies against himself,
that he found it necessary to leave Vienna, and to carry with him his
wife and children. He repaired to Holland, and settled at Haerlem in
1678. Here he was likely to have been successful; but his enemies from
Vienna followed him, and obliged him to leave Holland. In 1680 we
find him in Great Britain, where he examined the Scottish lead-mines,
and smelting-works; and in 1681, and 1682, he traversed Cornwall, and
studied the mines and smelting-works of that great mining county; here
he suggested several improvements and ameliorations. Soon after this
an advantageous proposal was made to him by the Duke of Mecklenburg
Gustrow, by means of Count Zinzendorf; but all his projects were
arrested by his death, which took place in the year 1682. It is said
that he died in London, but I have not been able to find any evidence
of this.
It would be a difficult task to particularize his various discoveries,
which are scattered through a multiplicity of writings. He was
undoubtedly the first discoverer of boracic acid, though the credit of
the discovery has usually been given to Homberg.[179] But then he gives
no account of boracic acid, nor does he seem to have attended to its
qualities. The following is a list of Beccher’s writings:
[179] In the sixth chemical thesis, in the second supplement to the
Physica Subterranea (page 791, Stahl’s Edition. Lipsiæ, 1703), he says,
“ubi etiam, continuato igne, ipsum sal volatile acquires, quod eadem
methodo cum vitriolo seu spiritu aut oleo vitrioli, et oleo tartari,
vel _borace_ succedit.”
1. Metallurgia, or the Natural Science of Metals.
2. Institutiones Chymicæ.
3. Parnassus Medicinalis illustrata.
4. Œdipus Chymicus seu Institutiones Chymicæ.
5. Acta laboratorii Chymici Monacensis seu Physica Subterranea.--This,
which is the most important of all his works, is usually known by the
name of “Physica Subterranea.” This is the sole title affixed to it in
the edition published at Leipsic, in 1703, to which Stahl has prefixed
a long introduction. It is divided into seven sections. In the first he
treats of the creation of the world; in the second he gives a chemical
account of the motions and changes which are constantly going on in the
earth; in the third he treats of the three principles of all bodies,
which he calls _earths_. The first of these principles of metals and
stones is the _fusible_ or _stony earth_; the second principle of
minerals is the _fat earth_, improperly called _sulphur_; the third
principle is the _fluid earth_, improperly called _mercury_; in the
fourth section he treats of the action of subterraneous principles, or
the formation of _mixts_; in the fifth he treats of the solution of the
three classes of mixts, animals, vegetables, and metals; in the sixth
he treats of _mixts_, in which he gives their chemical constituents.
This section is very curious, because it gives Beccher’s views of the
constitution of compound bodies. It will be seen from it that he had
much more correct notions of the real objects of chemistry, than any of
his contemporaries. In the seventh and last section he treats of the
accidents and physical affections of subterraneous bodies.
6. Experimentum Chymicum novum quo artificialis et instantanea
metallorum generatio et transmutatio, ad oculum demonstratur.--This
constitutes the first supplement to the Physica Subterranea.
7. Supplementum secundum in Physicam subterraneam, demonstratio
philosophica seu Theses Chymicæ, veritatem et possibilitatem
transmutationis metallorum in aurum evincentes.
8. Trifolium Beccherianum Hollandicum.
9. Experimentum novum et curiosum de Minera arenaria perpetua, sive
prodromus historiæ seu propositionis Præp. D.D. Hollandiæ ordinibus ab
authore factæ, circa auri extractionem mediante arena littorali per
modum mineræ perpetuæ seu operationis magnæ fusoriæ cum emolumento.
Loco supplementi tertii in Physicam suam subterraneam.
10. Chemical Luckpot, or great chemical agreement; in a collection of
one thousand five hundred chemical processes.
11. Foolish Wisdom and wise Folly.
12. Magnalia Naturæ.
13. Tripus Hermeticus fatidicus pandens oracula chemica; seu I.
Laboratorium portatile, cum methodo vere spagyricæ seu juxta exigentiam
naturæ laborandi. Accessit pro praxi et exemplo; II. Centrum mundi
concatenatum seu Duumviratus hermeticus s. magnorum duorum productorum
nitri et salis textura et anatomia atque in omnium præcedentium
confirmationem adjunctum est; III. Alphabetum Minerale seu viginti
quatuor theses de subterraneorum mineralium genesi, textura et analysi;
his accessit concordantia mercurii lunæ et menstruorum.
14. Chemical Rose-garden.
15. Pantaleon delarvatus.
16. Beccheri, Lancelotti, etc. Epistolæ quatuor Chemicæ.
Beccher’s great merit was the contrivance of a chemical theory, by
which all the known facts were connected together and deduced from one
general principle. But as this theory was adopted and considerably
modified by Stahl, it will be better to lay a sketch of it before the
reader, after mentioning a few particulars of the life and labours of
one of the most extraordinary men whom Germany has produced; a man who,
in spite of the moroseness and haughtiness of his character, and in
spite of the barbarity of his style, raised himself to the very first
rank as a man of science; and had the rare or almost unique fortune of
giving laws at the same time to two different and important sciences,
which he cultivated together, without letting his opinions respecting
the one influence him with regard to the other. These sciences were
chemistry and medicine.
George Ernest Stahl was born at Anspach, in the year 1660. He studied
medicine at Jena under George Wolfgang Wedel; and got his doctor’s
degree at the age of twenty-three. Immediately after this he began
his career as a public lecturer. In 1687 the Duke of Weimar gave him
the title of physician to the court. In 1694 he was named, at the
solicitation of Frederick Hoffmann, second professor of medicine in
the University of Halle, which had just been established. Hoffmann and
he were at that time great friends, though they afterwards quarrelled.
Both of them were men of the very highest talents and both were the
founders of medical systems which, of course, each was anxious to
support. Hoffmann had greatly the superiority in elegance and clearness
of style, and in all the amenities of polite manners. But perhaps the
moroseness of Stahl, and the obscurity, or rather mysticism of his
style, contributed equally with the more amiable qualities of Hoffmann
to excite the attention and produce the veneration with which he was
viewed by his pupils, and, indeed, by the world at large.
At Halle he continued as a teacher of medicine for twenty-two years. In
1716 he was appointed physician to the King of Prussia. In consequence
of this appointment he left Halle, and resided in Berlin, where he died
in the year 1734, in the seventy-fifth year of his age. Notwithstanding
the great figure that Stahl made as a chemist, there is no evidence
that he ever taught that science in any public school. The Berlin
Academy had been founded under the superintendence of Leibnitz, who was
its first president; and therefore existed when Stahl was in Berlin:
but, till it was renovated in 1745 by Frederick the Great, this academy
possessed but little activity, and could scarcely, therefore, have
stimulated Stahl to attend to chemical science. However, his Chymia
rationalis et experimentalis was published in 1720, while he resided
in Berlin. The same date is appended to the preface of his Fundamenta
Chymiæ; but, from some expressions in that preface, it must, I should
think, have been written, not by Stahl, but by some other person.[180]
I suspect that the book had been written by some of his pupils, from
the lectures of the author while at Halle. If this was really the
case, it is obvious that Stahl must have taught chemistry as well as
medicine in the University of Halle.
[180] “Primus in his facem prætulit Beccherus; eumque magno cum artis
progressu sequentem videmus in ostendenda corporum analysi et synthesi
chymica versatissimum et acutissimum--_Stahlium_.”
Stahl’s medical theory is not less deserving of notice than his
chemical. But it is not the object of this work to enter into medical
speculations. Like Van Helmont, he resolved all diseases into the
actions of the _soul_, which was not merely the former of the body, but
its ruler and regulator. When any of the functions are deranged, the
soul exerts itself to restore them again to their healthy state; and
she accomplishes this by what in common language is called disease.
The business of a medical man, then, is not to prevent diseases, or to
stop them short when they appear; because they are the efforts of the
soul, the _vis medicatrix naturæ_, to restore the deranged state of the
functions: but he must watch these diseases, and prevent the symptoms
from becoming too violent. He must assist nature to produce the
intended effect, and check her exertions when they become abnormal. It
was a kind of modification of this theory, or rather a mixture of the
Stahlian and Hoffmannian theories, that Dr. Cullen afterwards taught
in Edinburgh with so much eclat. And these opinions, so far as medical
theories have any influence on practice, still continue in some measure
prevalent. Indeed, much of the vulgar practice followed by medical men,
chiefly in consequence of the education which they have received, is
deduced from these two theories. But it would be too great a digression
from the object of this work to enter into any details: suffice it
to say, that the rival theories of Hoffmann and Stahl for many years
divided the medical world in Germany, if not in the greater part of
Europe. It was no small matter of exultation to so young a medical
school as Halle, to have at once within its walls two such eminent
teachers as Hoffmann and Stahl.
Let us turn our attention to the chemical writings of Stahl. Of
these the most important is his Fundamenta Chymiæ dogmaticæ et
experimentalis. It is divided, like the chemistry of Boerhaave, into a
theoretical and practical part. The perusal of it is very disagreeable,
as it is full of German words and phrases, and symbols are almost
constantly substituted for words, as was at that time the custom.
His definition of chemistry is much more exact than Boerhaave’s. It
is, according to him, the art of resolving compound bodies into their
constituents, and of again forming them by uniting these constituents
together.
He is inclined to believe with Beccher, that the simple principles are
four in number. The _mixts_ are compounds of these principles; and he
shows by the doctrine of permutations that if we suppose the simple
principles four, then the number of mixts will be 40,340. He treats in
the first place of _mixts_, _compounds_, and _aggregates_.
The first object of chemistry is _corruption_, the second _generation_.
Of these he treats at considerable length, giving an account of the
different chemical processes, and of the apparatus employed.
He next treats of _salts_, which he defines mixts composed of water
and earth, both simple and pure, and intimately united. The salts are
vitriol, alum, nitre, common salt, and sal ammoniac. He next treats of
more compound salts. These are sugar, tartar, salts from the animal and
salts from the mineral kingdom, and quicklime.
After this comes sulphur, cinnabar, antimony, the sulphur of vitriol,
the sulphur of nitre, resins, and distilled oils. Then he treats of
water, which he divides into aqua _humida_ or common water, and aqua
_sicca_ or mercury. Next he treats of earths, which are of two kinds,
viz., _friable earths_, such as _clay_, _loam_, sand, &c., and metallic
earths constituting the bases of the metals.
He next treats of the metals; and, as a preliminary, we have a
description of the method of smelting, and operating upon the different
metals. The metals are then described successively in the following
order: Gold, silver, copper, iron, tin, lead, bismuth, zinc, antimony.
To this part of the system are added three sections. The first treats
of mercuries, the second of the philosopher’s stone, and the third of
the universal medicine. We must not suppose that Stahl was a believer
in these ideal compositions; his object is merely to give a history of
the different processes which had been recommended by the alchymists.
The second part of his work is divided into two _tracts_. The first
tract contains three sections. The first of these treats of the nature
of solids and fluids, of solutions and menstrua, of the effects of heat
and fire, of effervescence and boiling, of volatilization, of fusion
and liquefaction, of distillation, of precipitation, of calcination
and incineration, of detonation, of amalgamation, of crystallization
and inspissation, and of the fixity and firmness of bodies. In the
second section we have an account of salts, and of their generation
and transmutation, of sulphur and inflammability, of phosphorus, of
colours, and of the nature of metals and minerals. In this article
he gives short definitions of these bodies, and shows how they may
be known. The bodies thus defined are gold, silver, iron, copper,
lead, tin, mercury, antimony, sulphur, arsenic, vitriol, common salt,
nitre, alum, sal ammoniac, alkalies, and salts; viz., muriatic acid,
sulphuric, nitric, and sulphurous.
In the third section he treats of the method of reducing metallic
calces, of the mode of separating metals from their scoriæ, of the mode
of making artificial gems, and finally of the mode of giving copper a
golden colour.
The second tract is divided into two parts. The first part is
subdivided into four sections. In the first section he treats of the
instruments of chemical motion, of fire, of air, of water, of the most
subtile earth or salt. In the second section he treats _de subjectis_,
under the several heads of dissolving aggregates, of triturations and
solutions, and of calcinations and combustions. In the third section
he treats of the object of chemistry under the following heads: Of
chemical corruption, consisting of compounds from liquids, of the
separation of solids and fluids, of mixts, of the solution of compounds
from solids. In the fourth section he treats of fermentation.
The second part of this second tract treats of chemical generation,
and is divided into two sections. In the first section he treats of
the aggregate collection of bodies into fluids and solids. The section
treats of compositions under the heads of volatile and solid bodies. He
gives in the last article an account of the combination of mixts.
The third and last part of this elaborate work discusses three
subjects; viz. _zymotechnia_ or _fermentation_, _halotechnia_, or the
production and properties of salts, and _pyrotechnia_, in which the
whole of the Stahlian doctrine of _phlogiston_ is developed. This
third part has all the appearance of having been notes written down by
some person during the lectures of Stahl: for it consists of alternate
sentences of Latin and German. It is not at all likely that Stahl
himself would have produced such a piebald work; but if he lectured in
Latin, as was at that time the universal custom, it was natural for a
person occupied in taking down the lectures, to write as far as was
possible in Latin, but when any of the Latin phrases were lost, or did
not immediately occur to memory, it were equally natural to write down
the meaning of what the professor stated in the language most familiar
to the writer, which was undoubtedly the German.
Another of Stahl’s works is entitled “Opusculum
Chymico-physico-medicum,” published at Halle in a thick quarto volume,
in the year 1715. It contains a great number of tracts, partly chemical
and partly medical, which it is needless to specify. Perhaps the most
curious of them all is his dissertation to show the way in which Moses
ground the golden calf to powder, dissolved it in water, and obliged
the children of Israel to drink it. He shows that a solution of hepar
sulphuris (_sulphuret of potassium_), has the property of dissolving
gold, and he draws as a conclusion from his experiments that this was
the artifice employed by Moses. We have in the same volume a pretty
detailed treatise on metallurgic pyrotechny and docimasy. This is the
more curious, because Stahl never appears to have frequented the mines
and smelting-houses of Germany. He must, therefore, have drawn his
information from books and from experiment.
Another of his books is entitled “Experimenta, Observationes,
Animadversiones, CCC. Numero.” An octavo volume, printed at Berlin
in 1731. Another of his books is entitled “Specimen Beccherianum.”
There are also two chemical books of Stahl, which I have seen only in
a French translation, viz., _Traité de Soufre_ and _Traité de Sels_.
These are the only chemical writings of Stahl that I have seen. There
are probably others; indeed I have seen the titles of several other
chemical works ascribed to him. But as it is doubtful whether he really
wrote them or not, I think it unnecessary to specify them here.
Stahl’s writings evince the great progress which chemistry had
made even since the time of Beccher. But it is difficult to say
what particular new facts, which appear first in his writings were
discovered by himself, and what by others. I shall not, therefore,
attempt any enumeration of them. His reasoning is more subtile, and his
views much more extensive and profound than those of his predecessors.
The great improvement which he introduced into chemistry was the
employment of _phlogiston_, to explain the phenomena of combustion
and calcination. This theory had been originally broached by Beccher,
from whom Stahl evidently borrowed it, but he improved and simplified
it so much that the whole credit of it was given to him. It was called
the Stahlian theory, and raised him to the highest rank among chemists.
The sole objects of chemists for thirty or forty years after his time
was to illucidate and extend his theory. It applied so happily to all
the known facts, and was supported by experiments, which appeared
so decisive that nobody thought of calling it in question, or of
interrogating nature in any other way than he had pointed out. It will
be requisite, therefore, before proceeding further with this historical
sketch, to lay the outlines of the phlogistic theory before the reader.
It was conceived by Beccher and Stahl that all _combustible_ bodies
are compounds. One of the constituents they supposed to be dissipated
during the combustion, while the other constituent remained behind.
Now when combustible bodies are subjected to combustion, some of them
leave an acid behind them; while others leave a fixed powdery matter,
possessing the properties of an _earth_, and called usually the _calx_
of the combustible body. The metals are the substances which leave
a calx behind them when burnt, and sulphur and phosphorus leave an
acid. With respect to those bodies that would not burn, chemists did
not speculate much at first; but afterwards they came to think that
they consisted of the fixed substance that remained after combustion.
Hence the conclusion was natural, that they had already undergone
combustion. Thus quicklime possessed properties very similar to the
calces of metals. It was natural, therefore, to consider it as a calx,
and to believe that if the matter dissipated during combustion could be
again restored, lime would be converted into a substance similar to the
metals.
Combustibility then, according to this view of the subject, depends
upon a principle or material substance, existing in every combustible
body, and dissipated during the combustion. This substance was
considered to be absolutely the same in all combustible bodies
whatever; hence the difference between combustible bodies proceeded
from the other principle or number of principles with which this common
substance is combined. In consequence of this identity Stahl invented
the term _phlogiston_, by which he denoted this common principle of
combustible bodies. Inflammation, with the several phenomena that
attend it, depended on the gradual separation of this principle,
which being once separated, what remained of the body could no
longer be an inflammable substance, but must be similar to the other
kinds of matter. It was this opinion that combustibility is owing
to the presence of phlogiston, and inflammation to its escape, that
constituted the peculiar theory of Beccher, and which was afterwards
illustrated by Stahl with so much clearness, and experiments to prove
its truth were advanced by him of so much force, that it came to be
distinguished by the name of the Stahlian theory.
The identity of phlogiston in all combustible bodies was founded upon
observations and experiments of so decisive a nature, that after the
existence of the principle itself was admitted, they could not fail
to be satisfactory. When phosphorus is made to burn it gives out a
strong flame, much heat is evolved, and the phosphorus is dissipated
in a white smoke: but if the combustion be conducted within a glass
vessel of a proper shape, this white smoke will be deposited on the
inside of the glass; it quickly absorbs moisture from the atmosphere,
and runs into an acid liquid, known by the name of phosphoric acid.
If this liquid be put into a platinum crucible, and gradually heated
to redness, the water is dissipated, and a substance remains which,
on cooling, congeals into a transparent colourless body like glass:
this is dry _phosphoric_ acid. If now we mix phosphoric acid with
a quantity of charcoal powder, and heat it sufficiently in a glass
retort, taking care to exclude the external air, a _portion_ or the
_whole_ of the charcoal will disappear, and phosphorus will be formed
possessed of the same properties that it had before it was subjected
to combustion. The conclusion deduced from this process appeared
irresistible; the charcoal, or a portion of it, had combined with the
phosphoric acid, and both together had constituted phosphorus.
Now, in changing phosphoric acid into phosphorus, we may employ almost
any kind of combustible substance that we please, provided it be
capable of bearing the requisite heat; they will all equally answer,
and will all convert the acid into phosphorus. Instead of charcoal we
may take lamp-black, or sugar, or resin, or even several of the metals.
Hence it was concluded that all of these bodies contain a common
principle which they communicate to the phosphoric acid; and since the
new body formed is in all cases identical, the principle communicated
must also be identical. Hence combustible bodies contain an identical
principle, and this principle is phlogiston.
Sulphur by burning is converted into sulphuric acid; and if sulphuric
acid be heated with charcoal, or phosphorus, or even sulphur, it is
again converted into sulphur. Several of the metals produce the same
effect. The reasoning here was the same as with regard to phosphoric
acid, and the conclusion was similar.
When lead is kept nearly at a red heat in the open air for some time,
being constantly stirred to expose new surfaces to the air, it is
converted into the beautiful pigment called _red lead_; this is a calx
of lead. To restore this calx again to the state of metallic lead, we
have only to heat it in contact with almost any combustible matter
whatever. Pit-coal, peat, charcoal, sugar, flour, iron, zinc, &c.,
all these bodies then must contain one common principle, which they
communicate to red lead, and by so doing convert it into lead. This
common principle is phlogiston.
These examples are sufficient to show the reader the way in which
Stahl proved the identity of phlogiston in all combustible bodies. And
the demonstration was considered as so complete that the opinion was
adopted by every chemist without exception.
When we inquire further, and endeavour to learn what qualities
phlogiston was supposed to have in its separate state, we find this
part of the subject very unsatisfactory, and the opinions very
unsettled. Beccher and Stahl represented phlogiston as a dry substance,
or of an earthy nature, the particles of which are exquisitely
subtile, and very much disposed to be agitated and set in motion with
inconceivable velocity. This was called by Stahl _motus verticillaris_.
When the particles of any body are agitated with this kind of motion,
the body exhibits the phenomena of heat or ignition, or inflammation,
according to the violence and rapidity of the motion.
This very crude opinion of the earthy nature of phlogiston, appears to
have been deduced from the insolubility of most combustible substances
in water. If we except alcohol, and ether, and gums, very few of
them are capable of being dissolved in that liquid. Thus the metals,
sulphur, phosphorus, oils, resins, bitumens, charcoal, &c., are well
known to be insoluble. Now, at the time that Beccher and Stahl lived,
insolubility in water was considered as a character peculiar to earthy
bodies; and as those bodies which contain a great deal of phlogiston
are insoluble in water, though the other constituents be very soluble
in that liquid, it was natural enough to conclude that phlogiston
itself was of an earthy nature.
But though the opinions of chemists about the nature and properties
of phlogiston in a separate state were unsettled, no doubts were
entertained respecting its existence, and respecting its identity in
all combustible bodies. Its presence or its absence produced almost
all the changes which bodies undergo. Hence chemistry and combustion
came to be in some measure identified, and a theory of combustion was
considered as the same thing with a theory of chemistry.
Metals were compounds of _calces_ and phlogiston. The different
species of metals depend upon the different species of calx which each
contains; for there are as many _calces_ (each simple and peculiar) as
there are metals. These calces are capable of uniting with phlogiston
in indefinite proportions. The calx united to a little phlogiston still
retains its earthy appearance--a certain additional portion restores
the calx to the state of a metal. An enormous quantity of phlogiston
with which some calces, as calx of manganese, are capable of combining,
destroys the metallic appearance of the body, and renders it incapable
of dissolving in acids.
The affinity between a metallic calx and phlogiston is strong; but the
facility of union is greatly promoted when the calx still retains a
little phlogiston. If we drive off the whole phlogiston we can scarcely
unite the calx with phlogiston again, or bring it back to the state of
a metal: hence the extreme difficulty of reducing the calx of zinc, and
even the red calx of iron.
The various colours of bodies are owing to phlogiston, and these
colours vary with every alteration in the proportion of phlogiston
present.
It was observed very early that when a metal was converted into a calx
its weight was increased. But this, though known to Beecher and Stahl,
does not seem to have had any effect on their opinions. Boyle, who does
not seem to have been aware of the phlogistic theory, though it had
been broached before his death, relates an experiment on tin which he
made. He put a given weight of it into an open glass vessel, and kept
it melted on the fire till a certain portion of it was converted into
a calx: it was now found to have increased considerably in weight. This
experiment he relates in order to prove the materiality of heat: in his
opinion a certain quantity of heat had united to the tin and occasioned
the increase of weight. This opinion of Boyle was incompatible with
the Stahlian theory: for the tin had not only increased in weight, but
had been converted into a calx. It was therefore the opinion of Boyle
that calx of tin was a combination of _tin_ and _heat_. It could not
consequently be true that calx of tin was tin deprived of phlogiston.
When this difficulty struck the phlogistians, which was not till long
after the time of Stahl, they endeavoured to evade it by assigning new
properties to phlogiston. According to them it is not only destitute
of weight, but endowed with a principle of levity. In consequence of
this property, a body containing phlogiston is always lighter than it
would otherwise be, and it becomes heavier when the phlogiston makes
its escape: hence the reason why calx of tin is heavier than the same
tin in the metallic state. The increase of weight is not owing, as
Boyle believed, to the fixation of heat in the tin, but to the escape
of phlogiston from it.
Those philosophic chemists, who thus refined upon the properties of
phlogiston, did not perceive that by endowing it with a principle of
levity, they destroyed all the other characters which they had assigned
to it. What is gravity? Is it not an attraction by means of which
bodies are drawn towards each other, and remain united? And is there
any reason for supposing that chemical attraction differs in its nature
from the other kinds of attraction which matter possesses? If, then,
phlogiston be destitute of gravity, it cannot possess any attraction
for other bodies; if it be endowed with a principle of levity, it must
have the property of repelling other bodies, for that is the only
meaning that can be attached to the term. But if phlogiston has the
property of repelling all other substances, how comes it to be fixed
in combustible bodies? It must be united to the calces or the acids,
which constitute the other principle of these bodies; and it could not
be united, and remain united, unless a principle of attraction existed
between it and these bases; that is to say, unless it possessed a
principle the very opposite of levity.
Thus the fact, that calces are heavier than the metals from which they
are formed, in reality overturned the whole doctrine of phlogiston;
and the only reason why the doctrine continued to be admitted after
the fact was known is, that in these early days of chemistry, the
balance was scarcely ever employed in experimenting: hence alterations
in weight were little attended to or entirely overlooked. We shall
see afterwards, that when Lavoisier introduced a more accurate mode
of experimenting, and rendered it necessary to compare the original
weights of the substances employed, with the weights of the products,
he made use of this very experiment of Boyle, and a similar one made
with mercury, to overturn the whole doctrine of phlogiston.
The phlogistic school being thus founded by Stahl, in Berlin, a race
of chemists succeeded him in that capital, who contributed in no
ordinary degree to the improvement of the science. The most deservedly
celebrated of these were Neumann, Pott, Margraaf, and Eller.
Caspar Neumann was born at Zullichau, in Germany, in 1682. He was
early received into favour by the King of Prussia, and travelled
at the expense of that monarch into Holland, England, France, and
Italy. During these travels he had an opportunity of making a
personal acquaintance with the most eminent men of science in all
the different countries which he visited. On his return home, in
1724, he was appointed professor of chemistry in the Royal College of
Physic and Surgery at Berlin, where he delivered a course of lectures
annually. During the remainder of his life he enjoyed the situation of
superintendent of the Royal Laboratory, and apothecary to the King of
Prussia. He died in 1737. He was a Fellow of the Royal Society, and
several papers of his appeared in the Transactions of that learned
body. The following is a list of these papers, all of which were
written in Latin:
1. Disquisitio de camphora.
2. De experimento probandi spiritum vini Gallici, per quam usitato, sed
revera falso et fallaci.
Some merchants in Holland, England, Hamburg, and Dantzic, were in
possession of what they considered an infallible test to distinguish
French brandy from every other kind of spirit. It was a dusky yellowish
liquid. When one or two drops of it were let fall into a glass of
French brandy, a beautiful blue colour appeared at the bottom of
the glass, and when the brandy is stirred, the whole liquid becomes
azure. But if the spirit tried be malt spirit, no such colour appears
in the glass. Neumann ascertained that the test liquid was merely a
solution of sulphate of iron in water, and that the blue colour was
the consequence of the brandy having been kept in oak casks, and thus
having dissolved a portion of tannin. Every spirit will exhibit the
same colour, if it has been kept in oak casks.
3. De salibus alkalino-fixis.
4. De camphora thymi.
5. De ambragrysea.
His other papers, published in Germany, are the following:
In the Ephemerides.
1. De oleo distillato formicorum æthereo.
2. De albumine ovi succino simili.
In the Miscellania Berolinensia.
1. Meditationes in binas observationes de aqua per putrefactionem
rubra, vulgo pro tali in sanguinem versa habita.
2. Succincta relatio exactis Pomeraniis de prodigio sanguinis in palude
viso.
3. De prodigio sanguinis ex Pomeranio nunciato.
4. Disquisitio de camphora.
5. De experimento probandi spiritum vini Gallicum.
6. De spiritu urinoso caustico.
7. Demonstratio syrupum violarum ad probanda liquida non sufficere.
8. Examen correctionis olei raparum.
9. De vi caustica et conversione salium alkalino-fixorum aëri
expositorum in salia neutra.
He published separately,
1. De salibus alkalino-fixis et camphora.
2. De succino, opio, caryophyllis aromaticis et castoreo.
3. On saltpetre, sulphur, antimony, and iron.
4. On tea, coffee, beer, and wine.
5. Disquisitio de ambragrysea.
6. On common salt, tartar, sal ammoniac and ants.
After Neumann’s death, two copies of his chemical lectures were
published. The first consisting of notes taken by one of his pupils,
intermixed with incoherent compilations from other authors, was printed
at Berlin in 1740. The other was printed by the booksellers of the
Orphan Hospital of Zullichau (the place of Neumann’s birth), and is
said to have been taken from the original papers in the author’s
handwriting. Of this last an excellent translation, with many additions
and corrections, was published by Dr. Lewis, in London, in the year
1759; it was entitled, “The Chemical Works of Caspar Neumann, M.D.,
Professor of Chemistry at Berlin, F.R.S., &c. Abridged and methodized;
with large additions, containing the later discoveries and improvements
made in Chemistry, and the arts depending thereon. By William
Lewis, M.B., F.R.S. London, 1759.” This is an excellent book, and
contains many things that still retain their value, notwithstanding
the improvements which have been made since in every department of
chemistry.
I have reason to believe that the laborious part of this translation
and compilation was made by Mr. Chicholm, whom Dr. Lewis employed as
his assistant. Mr. Chicholm, when a young man, went to London from
Aberdeen, where he had studied at the university, and acquired a
competent knowledge of Greek and Latin, but no means of supporting
himself. On his arrival in London, one of the first things that
struck his attention was a Greek book, placed open against the pane
of a bookseller’s window. Chicholm went up to the window, at which
he continued standing till he had perused the whole Greek page thus
exposed to his view. Dr. Lewis happened to be in the shop: he had
been looking out for a young man whom he could employ to take charge
of his laboratory, and manage his processes, and who should possess
sufficient intelligence to read chemical works for him, and collect
out of each whatever deserved to be known, either from its novelty
or ingenuity. The appearance and manners of Chicholm struck him, and
made him think of him as a man likely to answer the purposes which he
had in view. He called him into the shop, and after some conversation
with him, took him home, and kept him all his life as his assistant
and operator. Chicholm was a laborious and painstaking man, and by
continually working in Lewis’s laboratory, soon acquired a competent
knowledge of chemistry. He compiled several manuscript volumes, partly
consisting of his own experiments, and partly of collections from other
authors. At Dr. Lewis’s death, all his books were sold by auction, and
these manuscript volumes among the rest. They were purchased by Mr.
Wedgewood, senior, who at the same time took Mr. Chicholm into his
service, and gave him the charge of his own laboratory. It was Mr.
Chicholm that was the constructor of the well-known piece of apparatus
known by the name of Wedgewood’s pyrometer. After his death the
instrument continued still to be constructed for some time; but so many
complaints were made of the unequal contraction of the pieces, that
Mr. Wedgewood, junior, who had succeeded to the pottery in consequence
of the death of his father, put an end to the manufacture of them
altogether.
John Henry Pott was born at Halberstadt, in the year 1692. He was a
scholar of Hoffmann and Stahl, and from this last he seems to have
imbibed his taste for chemistry. He settled at Berlin, where he became
assessor of the Royal College of Medicine and Surgery, inspector of
medicines, superintendent of the Royal Laboratory, and dean of the
Academy of Sciences of Berlin. He was chosen professor of theoretical
chemistry at Berlin; and on the death of Neumann, in 1737, he succeeded
him as professor of practical chemistry. He was beyond question the
most learned and laborious chemist of his day. His erudition, indeed,
was very great; and his historical introductions to his dissertation
displays the extent of his reading on every subject of which he
had occasion to treat. It has often struck me that the historical
introductions which Bergmann has prefixed to his papers, are several
of them borrowed from Pott. The Lithogeognosia of Pott is one of the
most extraordinary productions of the age in which he lived. It was the
result of a request of the King of Prussia, to discover the ingredients
of which Saxon porcelain was made. Mr. Pott, not being able to procure
any satisfactory information relative to the nature of the substances
employed at Dresden, resolved to undertake a chemical examination
of all the substances that were likely to be employed in such a
manufacture. He tried the effect of fire upon all the stones, earths,
and minerals, that he could procure, both separately and mixed together
in various proportions. He made at least thirty thousand experiments
in six years, and laid the foundation for a chemical knowledge of these
bodies.[181] It is to this work of Pott that we are indebted for our
knowledge of the effects of heat upon various earthy bodies, and upon
mixtures of them. Thus he found that pure white clay, or mixtures of
pure clay and quartz-sand, would not fuse at any temperature which he
could produce; but clay, mixed with lime or with oxide of iron, enters
speedily into fusion. Clay also fuses with its own weight of borax; it
forms a compact mass with half its weight, and does not concrete into
a hard body when mixed with a third of its weight of that salt. Clay
fuses easily with fluor spar; it fuses, also, with twice its weight of
protoxide of lead, and with its own weight of sulphate of lime, but
with no other proportion tried. It was a knowledge of these mutual
actions of bodies on each other, when exposed to heat, that gradually
led to the methods of examining minerals by the blowpipe. These methods
were brought to the present state of perfection by Assessor Gahn, of
Fahlun, the result of whose labours has been published by Berzelius, in
his treatise on the blowpipe. Pott died in 1777, in the eighty-fifth
year of his age.
[181] There is a French translation of this work, entitled
“Litheognosie, ou Examen Chymique des Pierres et des Terres en
général, et du Talc de la Topaz, et de la Steatite en particulier;
avec une Dissertation sur le Feu et sur la Lumière.” Paris, 1753.
With a continuation, constituting a second volume, in which all the
experiments in the first volume are exhibited in the form of tables.
His different chemical works (his Lithogeognosia excepted) were
collected and translated into French by M. Demachy, in the year 1759,
and published in four small octavo volumes. The chemical papers
contained in these volumes are thirty-two in number. Some of these
papers cannot but appear somewhat extraordinary to a modern chemist:
for example, M. Duhamel had published in the memoirs of the French
Academy, in the year 1737, a set of experiments on common salt, from
which he deduced that its basis was a fixed alkali, which possessed
properties different from those of potash, and which of course required
to be distinguished by a peculiar name. It is sufficiently known that
the term _soda_ was afterwards applied to this alkali; by which name it
is known at present. Pott, in a very elaborate and long dissertation
on the base of common salt, endeavours to refute these opinions
of Duhamel. The subject was afterwards taken up by Margraaf, who
demonstrated, by decisive experiments, that the base of common salt is
_soda_; and that soda differs essentially in its properties from potash.
Pott’s dissertation on _bismuth_ is of considerable value. He collects
in it the statements and opinions of all preceding writers on this
metal, and describes its properties with considerable accuracy and
minuteness. The same observations apply to his dissertation on zinc.
John Theodore Eller, of Brockuser, was born on the 29th of November,
1689, at Pletzkau, in the principality of Anhalt Bernburg. He was
the fourth son of Jobst Hermann Eller, a man of a respectable
family, whose ancestors were proprietors of considerable estates in
Westphalia and the Netherlands. Young Eller received the rudiments
of his education in his father’s house, from which he went to the
University of Quedlinburg; and from thence to the University of Jena,
in 1709. He was sent thither to study law; but his passion was for
natural philosophy, which led him to devote himself to the study of
medicine. From Jena he went to Halle, and finally to Leyden, attracted
by the reputation of the older Albinus, of Professor Sengerd and the
celebrated Boerhaave, at that time in the height of his reputation.
The only practical anatomist then in Leyden, was M. Bidloo, an old man
of eighty, and of course unfit for teaching. This induced Eller to
repair to Amsterdam, to study under Rau, and to inspect the anatomical
museum of Ruysch. Bidloo soon dying, Rau was appointed his successor
at Leyden, whither Eller followed him, and dissected under him till
the year 1716. After taking his degree at Leyden, Eller returned to
Germany, and devoted a considerable time to the study and examination
of the mines of Saxony and the Hartz, and of the metallurgic processes
connected with these mines. From these mines he repaired to France, and
resumed his anatomical studies under Du Verney and Winslow. Chemistry
also attracted a good deal of his attention, and he frequented the
laboratories of Grosse, Lemery, Bolduc, and Homberg, at that time the
most eminent chemists in Paris.
From Paris he repaired to London, where he formed an acquaintance with
the numerous medical men of eminence who at that time adorned this
capital. On returning to Germany in 1721, he was appointed physician
to Prince Victor Frederick of Anhalt Bernburg. From Bernburg he
went to Magdeburg; and the King of Prussia called him to Berlin in
1724, to teach anatomy in the great anatomic theatre which had been
just erected. Soon after he was appointed physician to the king, a
counsellor and professor in the Royal Medico-Chirurgical College,
which had been just founded in Berlin. He was also appointed dean of
the Superior College of Medicine, and physician to the army and to
the great Hospital of Frederick. In the year 1755 Frederick the Great
made him a privy-counsellor, which is the highest rank that a medical
man can attain in Prussia. The same year he was made director of the
Royal Academy of Sciences of Berlin. He died in the year 1760, in the
seventy-first year of his age. He was twice married, and his second
wife survived him.
Many chemical papers of Eller are to be found in the memoirs of the
Berlin Academy. They were of sufficient importance, at the time when
he published them, to add considerably to his reputation, though not
sufficiently so to induce me to give a catalogue of them here. I am
not aware of any chemical discovery for which we are indebted to him;
but have been induced to give this brief notice of him, because he is
usually associated with Pott and Margraaf, making with them the three
celebrated chemists who adorned Berlin, during the splendid reign of
Frederick the Great.
Andrew Sigismund Margraaf was born in Berlin, in the year 1709, and
acquired the first principles of chemistry from his father, who was
an apothecary in that city. He afterwards studied under Neumann, and
travelling in quest of information to Frankfort, Strasburg, Halle, and
Freyburg, he returned to Berlin enriched with all the knowledge of his
favourite science which at that time existed. In 1760, on the death
of Eller, he was made director of the physical class of the Berlin
Academy of Sciences. He died in the year 1782, in the seventy-third
year of his age. He gradually acquired a brilliant reputation in
consequence of the numerous chemical papers which he successively
published, each of which usually contained a new chemical fact, of
more or less importance, deduced from a set of experiments generally
satisfactory and convincing. His papers have a greater resemblance
to those of Scheele than of any other chemist to whom we can compare
them. He may be considered as in some measure the beginner of chemical
analysis; for, before his time, the chemical analysis of bodies had
hardly been attempted. His methods, as might have been expected,
were not very perfect; nor did he attempt numerical results. His
experiments on phosphorus and on the method of extracting it from urine
are valuable; they communicated the first accurate notions relative
to this substance and to phosphoric acid. He first determined the
properties of the earth of alum, now known by the name of _alumina_;
showed that it differed from every other, and that it existed in clay,
and gave to that substance its peculiar properties. He demonstrated
the peculiar nature of soda, the base of common salt, which Pott had
called in question, and thus verified the conclusions of Duhamel. He
gives an easy process for obtaining pure silver from the chloride of
that metal: his method is to dissolve the pure chloride of silver in a
solution of caustic ammonia, and to put into the liquid a sufficient
quantity of pure mercury; the silver is speedily reduced and converted
into an amalgam, and when this amalgam is exposed to a red heat the
mercury is driven off and pure silver remains. The usual method of
reducing the chloride of silver is to heat it in a crucible with a
sufficient quantity of carbonate of potash, a process which was first
recommended by Kunkel. But it is scarcely possible to prevent the loss
of a portion of the silver when the chloride is reduced in this way.
The modern process is undoubtedly the simplest and the best, to reduce
it by means of hydrogen. If a few pieces of zinc be put into the bottom
of a beer-glass and some dilute sulphuric acid be poured over it an
effervescence takes place, and hydrogen gas is disengaged. Chloride of
silver, placed above the zinc in the same glass, is speedily reduced by
this hydrogen and converted into metallic silver.
Margraaf’s chemical papers, down to the time of publication, were
collected together, translated into French and published at Paris
in the year 1762, in two very small octavo volumes, they consist of
twenty-six different papers: some of the most curious and important
of which are those that have been just particularized. Several other
papers written by him appeared in the memoirs of the Berlin Academy,
after this collection of his works was published, particularly “A
demonstration of the possibility of drawing fixed alkaline salts
from tartar by means of acids, without employing the action of a
violent fire.” It was this paper, probably, that led Scheele, a few
years after, to his well-known method of obtaining tartaric acid, a
modification of which is still followed by manufacturers.
“Observations concerning a remarkable volatilization of a portion of
a kind of stone known by the names of flosse, flusse, fluor spar, and
likewise by that of hesperos: which volatilization was effectuated by
means of acids.” Pott had already shown the value of fluor spar as a
flux. Three years after the appearance of Margraaf’s paper, Scheele
discovered the nature of fluor spar, and first drew the attention of
chemists to the peculiar properties of fluoric acid.
In France, in consequence chiefly of the regulations established in
the Academy of Sciences, in the year 1699, a race of chemists always
existed, whose specific object was to cultivate chemistry, and extend
and improve it. The most eminent of these chemical labourers, after the
Stahlian theory was fully admitted in France till its credit began to
be shaken, were Reaumur, Hellot, Duhamel, Rouelle, and Macquer. Besides
these, who were the chief chemists in the academy, there were a few
others to whom we are indebted for chemical discoveries that deserve to
be recorded.
René Antoine Ferchault, Esq., Seigneur de Reaumur, certainly one of the
most extraordinary men of his age, was born at Rochelle, in 1683. He
went to the school of Rochelle, and afterwards studied philosophy under
the Jesuits at Poitiers. Hence he went to Bourges, to which one of his
uncles, canon of the holy chapel in that city, had invited him. At this
time he was only seventeen years of age, yet his parents ventured to
intrust a younger brother to his care, and this care he discharged
with all the fidelity and sagacity of a much older man. Here he devoted
himself to mathematics and physics, and he soon after went to Paris to
improve the happy talents which he had received from nature. He was
fortunate enough to meet with a friend and relation in the president,
Henault, equally devoted to study with himself, equally eager for
information, and possessed of equal honour and integrity, and equally
promising talents.
He came to Paris in 1703. In 1708 he was admitted into the Academy of
Sciences, in the situation of _élève_ of M. Varignon, vacant by the
promotion of M. Saurin to the rank of associate.
The first papers of his which were inserted in the Memoirs of the
Academy were geometrical: he gave a general method of finding an
infinity of curves, described by the extremity of a straight line,
the other extremity of which, passing along the surface of a given
curve, is always obliged to pass through the same point. Next year he
gave a geometrical work on Developes; but this was the last of his
mathematical tracts. He was charged by the academy with the task of
giving a description of the arts, and his taste for natural history
began to draw to that study the greatest part of his attention. His
first work as a naturalist was his observations on the formation of
shells. It was unknown whether shells increase by intussusception, like
animal bodies, or by the exterior and successive addition of new parts.
By a set of delicate observations he showed that shells are formed by
the addition of new parts, and that this was the cause of the variety
of colour, shape, and size which they usually affect. His observations
on snails, with a view to the way in which their shells are formed,
led him to the discovery of a singular insect, which not only lives on
snails, but in the inside of their bodies, from which it never stirs
till driven out by the snail.
During the same year, he wrote his curious paper on the silk of
spiders. The experiments of M. Bohn had shown that spiders could spin
a silk that might be usefully employed. But it remained to be seen
whether these creatures could be fed with profit, and in sufficiently
great numbers to produce a sufficient quantity of silk to be of use.
Reaumur undertook this disagreeable task, and showed that spiders could
not be fed together without attacking and destroying one another.
The next research which he undertook, was to discover in what way
certain sea-animals are capable of attaching themselves to fixed
bodies, and again disengaging themselves at pleasure. He discovered the
various threads and pinnæ which some of them possess for this purpose,
and the prodigious number of limbs by which the sea-star is enabled to
attach itself to solid bodies. Other animals employ a kind of cement
to glue themselves to those substances to which they are attached,
while some fix themselves by forming a vacuum in the interval between
themselves and the solid substances to which they are attached.
It was at this period that he found great quantities of the buccinum,
which yielded the purple dye of the ancients, upon the coast of Poitou.
He observed, also, that the stones and little sandy ridges round which
the shellfish had collected were covered with a kind of oval grains,
some of which were white, and others of a yellowish colour, and having
collected and squeezed some of these upon the sleeve of his shirt, so
as to wet it with the liquid which they contained, he was agreeably
surprised in about half an hour to find the wetted spot assume a
beautiful purple colour, which was not discharged by washing. He
collected a number of these grains, and carrying them to his apartment,
bruised and squeezed different parcels of them upon bits of linen; but
to his great surprise, after two or three hours, no colour appeared
on the wetted part; but, at the same time, two or three spots of the
plaster at the window, on which drops of the liquid had fallen, had
become purple; though the day was cloudy. On carrying the pieces
of linen to the window, and leaving them there, they also acquired
a purple colour. It was the action of light, then, on the liquor,
that caused it to tinge the linen. He found, likewise, that when the
colouring matter was put into a phial, which filled it completely, it
remained unchanged; but when the phial was not full, and was badly
corked, it acquired colour. From these facts it is evident, that the
purple colour is owing to the joint action of the light and the oxygen
of the atmosphere upon the liquor of the shellfish.
About this time, likewise, he made experiments upon a subject which
attracted the attention of mechanicians--to determine whether the
strength of a cord was greater, or less, or equal to the joint strength
of all the fibres which compose it. The result of Reaumur’s experiments
was, that the strength of the cord is less than that of all the fibres
of which it is composed. Hence it follows, that the less that a cord
differs from an assemblage of straight fibres, the stronger it is.
This, at that time considered as a singular mechanical paradox, was
afterwards elucidated by M. Duhamel.
It was a popular opinion of all the inhabitants of the sea-shore, that
when the claws of crabs, lobsters, &c., are lost by any means, they are
gradually replaced by others, and the animal in a short time becomes as
perfect as at first. This opinion was ridiculed by men of science as
inconsistent with all our notions of true philosophy. Reaumur subjected
it to the test of experiment, by removing the claws of these animals,
and keeping them alone for the requisite time in sea-water: new claws
soon sprang out, and perfectly replaced those that had been removed.
Thus the common opinion was verified,and the contemptuous smile of the
half-learned man of science was shown to be the result of ignorance,
not of knowledge.
Reaumur was not so fortunate in his attempts to explain the nature of
the shock given by the torpedo; which we now know to be an electric
shock produced by a peculiar apparatus within the animal. Reaumur
endeavoured to prove, from dissection, that the shock was owing to the
prodigious rapidity of the blow given by the animal in consequence of a
peculiar structure of its muscles.
The turquoise was at that time, as it still is, considerably admired in
consequence of the beauty of its colour. Persia was the country from
which this precious stone came, and it was at that time considered as
the only country in the universe where it occurred. Reaumur made a set
of experiments on the subject and showed that the fossil bones found in
Languedoc, when exposed to a certain heat, assume the same beautiful
green colour, and become turquoises equally beautiful with the Persian.
It is now known, that the true Persian turquoise, the _calamite_
of mineralogists, is quite different from fossil bones coloured
with copper. So far, therefore, Reaumur deceived himself by these
experiments; but at that time chemical knowledge was too imperfect to
enable him to subject Persian turquoise to an analysis, and determine
its constitution.
About the same period, he undertook an investigation of the nature
of imitation pearls, which resemble the true pearls so closely, that
it is very difficult, from appearances, to distinguish the true from
the false. He showed that the substance which gave the false pearls
their colour and lustre, was taken from a small fish called by the
French _able_, or _ablette_. He likewise undertook an investigation
of the origin of true pearls, and showed that they were indebted for
their production to a disease of the animal. It is now known, that
the introduction of any solid body, as a grain of sand, within the
shell of the living pearl-shellfish, gives occasion to the formation
of pearl. Linnæus boasted that he knew a method of forming artificial
pearls; and doubtless his process was merely introducing some solid
particle of matter into the living shell. Pearls consist of alternate
layers of carbonate of lime and animal membrane; and the colour and
lustre to which they owe their value depends upon the thinness of the
alternate coats.
The next paper of Reaumur was an account of the rivers in France
whose sand yielded gold-dust, and the method employed to extract the
gold. This paper will well repay the labour of a perusal; it owes its
interest in a great measure to the way in which the facts are laid
before the reader.
His paper on the prodigious bank of fossil shells at Touraine, from
which the inhabitants draw manure in such quantities for their fields,
deserves attention in a geological point of view. But his paper on
flints and stones is not so valuable; it consists in speculations,
which, from the infant state of chemical analysis when he wrote, could
not be expected to lead to correct conclusions.
I pass over many of the papers of this most indefatigable man, because
they are not connected with chemistry; but his history of insects
constitutes a charming book, and contains a prodigious number of facts
of the most curious and important nature. This book alone, supposing
Reaumur had done nothing else, would have been sufficient to have
immortalized the author.
In the year 1722 he published his work on the _art of converting iron
into steel, and of softening cast-iron_. At that time no steel whatever
was made in France; the nation was supplied with that indispensable
article from foreign countries, chiefly from Germany. The object of
Reaumur’s book was to teach his countrymen the art of making steel,
and, if possible, to explain the nature of the process by which iron
is changed into steel. Reaumur concluded from his experiments, that
steel is iron impregnated with _sulphureous_ and _saline_ matters. The
word _sulphureous_, as at that time used, was nearly synonymous with
our present term _combustible_. The process which he found to answer,
and which he recommends to be followed, was to mix together
4 parts of soot
2 parts of charcoal-powder
2 parts of wood-ashes
1½ parts of common salt.
The iron bars to be converted into steel were surrounded with this
mixture, and kept red-hot till converted into steel. Reaumur’s notion
of the difference between iron and steel was an approximation to
the truth. The saline matters which he added do not enter into the
composition of steel; and if they did, so far from improving, they
would injure its qualities. But the charcoal and soot, which consist
chiefly of carbon, really produce the desired effect; for steel is a
combination of _iron_ and _carbon_.
In consequence of these experiments of Reaumur, it came to be an
opinion entertained by chemists, that steel differed from iron merely
by containing a greater proportion of phlogiston; for the charcoal
and soot with which the iron bars were surrounded was considered as
consisting almost entirely of phlogiston; and the only useful purpose
which they could serve, was supposed to be to furnish phlogiston. This
opinion continued prevalent till it was overturned towards the end of
the last century, first by the experiments of Bergmann, and afterwards
by those of Berthollet, Vandermond, and Monge, published in the Memoirs
of the French Academy for 1786 (page 132). In this elaborate memoir the
authors take a view of all the different processes followed in bringing
iron from the ore to the state of steel: they then give an account of
the researches of Reaumur and of Bergmann; and lastly relate their own
experiments, from which they finally draw, as a conclusion, that steel
is a compound of iron and carbon.
The regent Orleans, who at that time administered the affairs of
France, thought that this work of Reaumur was deserving a reward, and
accordingly offered him a pension of 12,000 livres. Reaumur requested
of the regent that this pension should be given in the name of the
academy, and that after his death it should continue, and be devoted to
defray the necessary expenses towards bringing the arts into a state of
perfection. The request was granted, and the letters patent made out on
the 22d of December, 1722.
At that time tin-plate, as well as steel, was not made in France;
but all the tin-plates wanted were brought from Germany, where the
processes followed were kept profoundly secret. Reaumur undertook to
discover a method of tinning iron sufficiently cheap to admit the
article to be manufactured in France--and he succeeded. The difficulty
consisted in removing the scales with which the iron plates, as
prepared, were always covered. These scales consist of a vitrified
oxide of iron, to which the tin will not unite. Reaumur found, that
when these plates are steeped in water acidulated by means of bran,
and then allowed to rust in stoves, the scales become loose, and are
easily detached by rubbing the plates with sand. If after being thus
cleansed they are plunged into melted tin, covered with a little tallow
to prevent oxidizement, they are easily tinned. In consequence of this
explanation of the process by Reaumur, tin-plate manufactories were
speedily established in different parts of France. It was about the
same time, or only a little before it, that tin-plate manufactories
were first started in England. The English tin-plate was much more
beautiful than the German, and therefore immediately preferred to it;
because in Germany the iron was converted into plates by hammering,
whereas in England it was rolled out. This made it much smoother, and
consequently more beautiful.
Another art, at that time unknown in France, and indeed in every part
of Europe except Saxony, was the art of making porcelain, a name given
to the beautiful translucent stoneware which is brought from China and
Japan. Reaumur undertook to discover the process employed in making
it. He procured specimens of porcelain from China and Japan, and also
of the imitations of those vessels at that time made in various parts
of France and other European countries. The true porcelain remained
unaltered, though exposed to the most violent heat which he was capable
of producing; but the imitations, in a furnace heated by no means
violently, melted into a perfect glass. Hence he concluded, that the
imitation-porcelains were merely glass, not heated sufficiently to be
brought into fusion; but true porcelain he conceived to be composed
of two different ingredients, one of which is capable of resisting
the most violent heat which can be raised, but the other, when heated
sufficiently, melts into a glass. It is this last ingredient that gives
porcelain its translucency, while the other makes it refractory in
the fire. This opinion of Reaumur was soon after confirmed by Father
d’Entrecolles, a French missionary in China, who sent some time after
a memoir to the academy, describing the mode followed by the Chinese
in the manufactory of their porcelain. Two substances are employed
by them, the one called _kaolin_ and the other _petunse_. It is now
known that _kaolin_ is what we call porcelain-clay, and that _petunse_
is a fine white felspar. Felspar is fusible in a violent heat, but
porcelain-clay is refractory in the highest temperatures that we have
it in our power to produce in furnaces.
Reaumur made another curious observation on glass, which has been,
since his time, employed very successfully to explain the appearances
of many of our trap-rocks. If a glass vessel, properly secured in
sand, be raised to a red heat, and then allowed to cool very slowly,
it puts off the appearance of glass and assumes that of stoneware, or
porcelain. Vessels thus altered have received the name of _Reaumur’s
porcelain_. They are much more refractory than glass, and therefore
may be exposed to a pretty strong red heat without any danger of
softening or losing their shape. This change is occasioned by the
glass being kept long in a soft state: the various substances of
which it is composed are at liberty to exercise their affinities
and to crystallize. This makes the vessel lose its glassy structure
altogether. In like manner it was found by Sir James Hall and Mr.
Gregory Watt, that when common greenstone was heated sufficiently,
and then rapidly cooled, it melted and concreted into a glass; but if
after having been melted it was allowed to cool exceedingly slowly, the
constituents again crystallized and arranged themselves as at first--so
that a true greenstone was again formed. In the same way lavas from a
volcano either assume the appearance of slag or of stone, according as
they have cooled rapidly or slowly. Many of the lavas from Vesuvius
cannot be distinguished from our _greenstones_.
Reaumur’s labours upon the thermometer must not be omitted here;
because he gave his name to a thermometer, which was long used in
France and in other parts of Europe. The first person that brought
thermometers into a state capable of being compared with each other
was Sir Isaac Newton, in a paper published in the Philosophical
Transactions for 1701. Fahrenheit, of Amsterdam, was the first person
that put Newton’s method in practice, by fixing two points on his
scale, the freezing-water point and the boiling-water point, and
dividing the interval between them into one hundred and eighty degrees.
But no fixed point existed in the thermometers employed in France,
every one graduating them according to his fancy; so that no two
thermometers could be compared together. Reaumur graduated his
thermometers by plunging them into freezing water or a mixture of
snow and water. This point was marked zero, and was called the
freezing-water point. The liquid used in his thermometers was spirit
of wine: he took care that it should be always of the same strength,
and the interval between the point of freezing and boiling water
was divided into eighty degrees. Deluc afterwards rectified this
thermometer, by substituting mercury for spirit of wine. This not only
enabled the thermometer to be used to measure higher temperatures,
but corrected an obvious error which existed in all the thermometers
constructed upon Reaumur’s principle: for spirit of wine cannot bear
a temperature of eighty degrees Reaumur without being dissipated
into vapour--absolute alcohol boiling at a hundred and sixty-two
degrees two-thirds. It is obvious from this, that the boiling point in
Reaumur’s thermometer could not be accurate, and that it would vary,
according to the quantity of empty space left above the alcohol.
Finally, he contrived a method of hatching chickens by means of
artificial heat, as is practised in Egypt.
We are indebted to him also for a set of important observations on the
organs of digestion in birds. He showed, that in birds of prey, which
live wholly upon animal food, digestion is performed by solvents in
the stomach, as is the case with digestion in man: while those birds
that live upon vegetable food have a very powerful stomach or gizzard,
capable of triturating the seeds which they swallow. To facilitate this
triturating process, these fowls are in the habit of swallowing small
pebbles.
The moral qualities of M. Reaumur seem not to have been inferior to the
extent and variety of his acquirements. He was kind and benevolent, and
remarkably disinterested. He performed the duties of intendant of the
order of St. Louis from the year 1735 till his death, without accepting
any of the emoluments of the office, all of which were most religiously
given to the person to whom they belonged, had she been capable of
performing the duties of the place. M. Reaumur died on the 17th of
October, 1756, after having lived very nearly seventy-five years.
John Hellot was born in Paris in the year 1685, on the 20th of
November. His father, Michael Hellot, was of a respectable family, and
the early part of his son’s education was at home: it seems to have
been excellent, as young Hellot acquired the difficult art of writing
on all manner of subjects in a precise, clear, and elegant style. His
father intended him for the church; but his own taste led him decidedly
to the study of chemistry. He had an uncle a physician, some of whose
papers on chemical subjects fell into his hands. This circumstance
kindled his natural taste into a flame: he formed an acquaintance with
M. Geoffroy, whose reputation as a chemist was at that time high, and
this friendship was afterwards cemented by Geoffroy marrying the niece
of M. Hellot.
His circumstances being easy, he went over to England, to form a
personal acquaintance with the many eminent philosophers who at that
time adorned that country. His fortune was considerably deranged by
Law’s celebrated scheme during the regency of the Duke of Orleans. This
obliged him to look out for some resource: he became editor of the
Gazette de France, and continued in this employment from 1718 to 1732.
During these fourteen years, however, he did not neglect chemistry,
though his progress was not so rapid as it would have been, could he
have devoted to that science his undivided attention. In 1732 he was
put forward by his friends as a candidate for a place in the Academy of
Sciences; and in the year 1735 he was chosen adjunct chemist, vacant by
the promotion of M. de la Condamine to the place of associate. Three
years after he was declared a supernumerary pensioner, without passing
through the step of associate. His reputation as a chemist was already
considerable, and after he became a member of the academy, he devoted
himself to the investigations connected with his favourite science.
His first labours were on zinc; in two successive papers he endeavoured
to decompose this metal, and to ascertain the nature of its
constituents. Though his labour was unsuccessful, yet he pointed out
many new properties of this metal, and various new compounds into which
it enters. Neither was he more successful in his attempt to account for
the origin of the red vapours which are exhaled from nitre in certain
circumstances. He ascribed them to the presence of ferruginous matters
in the nitre; whereas they are owing to the expulsion and partial
decomposition of the nitric acid of the nitre, in consequence of the
action of some more powerful acid.
His paper on sympathetic ink is of more importance. A German chemist
had shown him a saline solution of a red colour which became blue when
heated: this led him to form a sympathetic ink, which was pale red,
while the paper was moist, but became blue upon drying it by holding it
to the fire. This sympathetic ink was a solution of cobalt in muriatic
acid. It does not appear from Hellot’s paper that he was exactly aware
of the chemical constitution of the liquid which constituted his
sympathetic ink; though it is clear he knew that cobalt constitutes an
essential part of it.
Kunkel’s phosphorus, though it had been originally discovered in
Germany, could not be prepared by any of the processes which had been
given to the public. Boyle had taught his operator, Godfrey Hankwitz,
the method of making it. This man had, after Boyle’s death, opened a
chemist’s shop in London, and it was he that supplied all Europe with
this curious article: on that account it was usually distinguished
by the name of _English phosphorus_. But in the year 1737 a stranger
appeared in Paris, who offered for a stipulated reward to communicate
the method of manufacturing this substance to the Academy of Sciences.
The offer was accepted by the French government, and a committee of
the academy, at the head of which was Hellot, was appointed to witness
the process, and ascertain all its steps. The process was repeated
with success; and Hellot drew up a minute detail of the whole, which
was inserted in the Memoirs of the Academy, for the year 1737. The
publication of this paper constitutes an era in the preparation of
phosphorus: it was henceforward in the power of every chemist to
prepare it for himself. A few years after the process was much improved
by Margraaf; and, within little more than twenty years after, the very
convenient process still in use was suggested by Scheele. Hellot’s
experiments on the comparative merits of the salts of Peyrac, and of
Pecais were of importance, because they decided a dispute--they may
also perhaps be considered as curiosities in an historical point of
view; because we see from them the methods which Hellot had recourse to
at that early period in order to determine the purity of common salt.
They are not entitled, however, to a more particular notice here.
In the year 1740 M. Hellot was charged with the general inspection of
dyeing; a situation which M. du Foy had held till the time of his death
in 1739. It was this appointment, doubtless, which turned his attention
to the theory of dyeing, which he tried to explain in two memoirs read
to the academy in 1740 and 1741. The subject was afterwards prosecuted
by him in subsequent memoirs which were published by the academy.
In 1745 he was named to go to Lyons in order to examine with care the
processes followed for refining gold and silver. Before his return
he took care to give to these processes the requisite precision and
exactness. Immediately after his return to Paris he was appointed to
examine the different mines and assay the different ores in France;
this appointment led him to turn his thoughts to the subject. The
result of this was the publication of an excellent work on assaying
and metallurgy, entitled “De la Fonte des Mines, des Fonderies, &c.
Traduit de l’Allemand de Christophe-André Schlutter.” The first volume
of this book appeared in 1750, and the second in 1753. Though this book
is called by Hellot a translation, it contains in fact a great deal
of original matter; the arrangement is quite altered; many processes
not noticed by Schlutter are given, and many essential articles are
introduced, which had been totally omitted in the original work. He
begins with an introduction, in which he gives a short sketch of all
the mines existing in every part of France, together with some notice
of the present state of each. The first volume treats entirely of
docimasy, or the art of assaying the different metallic ores. Though
this art has been much improved since Hellot’s time, yet the processes
given in this volume are not without their value. The second volume
treats of the various metallurgic processes followed in order to
extract metals from their ores. This volume is furnished with no fewer
than fifty-five plates, in which all the various furnaces, &c. used in
these processes are exhibited to the eye.
While occupied in preparing this work for the press he was chosen to
endeavour to bring the porcelain manufactory at Sevre to a greater
state of perfection than it had yet reached. In this he was successful.
He even discovered various new colours proper for painting upon
porcelain; which contributed to give to this manufactory the celebrity
which it acquired.
In the year 1763 a phenomenon at that time quite new to France took
place in the coal-mine of Briançon. A quantity of carburetted hydrogen
gas had collected in the bottom of the mine, and being kindled by
the lights employed by the miners, it exploded with great violence,
and killed or wounded every person in the mine. This destructive gas,
distinguished in this country by the name of _fire-damp_, had been
long known in Great Britain and in the Low Countries, though it had
not before been known in France. The Duke de Choiseul, informed of
this event, had recourse to the academy for assistance, who appointed
Messrs. de Montigny, Duhamel, and Hellot, a committee to endeavour
to discover the remedies proper to prevent any such accident from
happening for the future. The report of these gentlemen was published
in the Memoirs of the Academy;[182] they give an account both of the
fire-damp, and _choke-damp_, or _carbonic acid gas_, which sometimes
also makes its appearance in coal-mines. They very justly observe
that the proper way to obviate the inconveniency of these gases is to
ventilate the mine properly; and they give various methods by which
this ventilation may be promoted by means of fires lighted at the
bottom of the shaft, &c.
[182] 1763, p. 235.
In 1763 M. Hellot was appointed, conjointly with M. Tillet, to examine
the process followed for assaying gold and silver. They showed that the
cupels always retained a small portion of the silver assayed, and that
this loss, ascribed to the presence of a foreign metal, made the purity
of the silver be always reckoned under the truth, which occasioned a
loss to the proprietor.
His health continued tolerably good till he reached his eightieth year:
he was then struck with palsy, but partially recovered from the first
attack; but a second attack, on the 13th of February, 1765, refused
to yield to every medical treatment, and he died on the 15th of that
month, at an age a little beyond eighty.
Henry Louis Duhamel du Monceau was born at Paris in the year 1700.
He was descended from Loth Duhamel, a Dutch gentleman, who came to
France in the suite of the infamous Duke of Burgundy, about the year
1400. Young Duhamel was educated in the College of Harcourt; but the
course of study did not suit his taste. He left it with only one fact
engraven on his memory--that men, by observing nature, had created a
science called _physics_; and he resolved to profit by his freedom
from restraint and turn the whole of his attention to that subject. He
lodged near the Jardin du Roi, where alone, at that time, physics were
attended to in Paris. Dufoy, Geoffroy, Lemery, Jussieu, and Vaillant,
were the friends with whom he associated on coming to Paris. His
industry was stimulated solely by a love of study, and by the pleasure
which he derived from the increase of knowledge; love of fame does not
appear to have entered into his account.
In the year 1718 saffron, which is much cultivated in that part of
France formerly distinguished by the name of Gâtinois, where Duhamel’s
property lay, was attacked by a malady which appeared contagious.
Healthy bulbs, when placed in the neighbourhood of those that were
diseased, soon became affected with the same malady. Government
consulted the academy on the subject; and this learned body thought
they could not do better than request M. Duhamel to investigate the
cause of the disease; though he was only eighteen years of age, and
not even a member of the academy. He ascertained that the malady was
owing to a parasitical plant, which attached itself to the bulb of the
saffron, and drew nourishment from it. This plant extended under the
earth, from one bulb to another, and thus infected the whole saffron
plantations.
M. Duhamel formed the resolution at the commencement of his scientific
career to devote himself to public utility, and to prosecute those
subjects which were likely to contribute most effectually to the
comfort of the lower ranks of men. Much of his time was spent in
endeavouring to promote the culture of vegetables, and in rendering
that culture more useful to society. This naturally led to a careful
study of the physiology of trees. The fruit of this study he gave to
the world in the year 1758, when his Physique des Arbres was published.
This constitutes one of the most important works on the subject which
has ever appeared. It contains a great number of new and original
facts; and contributed very much indeed to advance this difficult, but
most important branch of science: nor is it less remarkable for modesty
than for value. The facts gathered from other sources, even those
which make against his own opinions, are most carefully and accurately
stated: the experiments that preceded his are repeated and verified
with much care; and the reader is left to discover the new facts and
new views of the author, without any attempt on his part to claim them
as his own.
M. Duhamel had been attached to the department of the marine by M. de
Maurepas, who had given him the title of _inspector-general_. This led
him to turn his attention to naval science in general. The construction
of vessels, the weaving of sailcloths, the construction of ropes and
cables, the method of preserving the wood, occupied his attention
successively, and gave birth to several treatises, which, like all
his works, contain immense collections of facts and experiments. He
endeavours always to discover which is the best practice, to reduce
it to fixed rules, and to support it by philosophical principles; but
abstains from all theory when it can be supported only by hypothesis.
From the year 1740, when he became an academician, till his death
in 1781, he made a regular set of meteorological observations at
Pithiviers, with details relative to the direction of the needle, to
agriculture, to the medical constitution of the year, and to the time
of nest-building, and of the passage of birds.
Above sixty memoirs of his were published in the Transactions of the
French Academy of Sciences. They are so multifarious in their nature,
and embrace such a variety of subjects, that I shall not attempt even
to give their titles, but satisfy myself with stating such only as bear
more immediately upon the science of chemistry.
It will be proper in conducting this review to notice the result of
his labours connected with the ossification of bones; because, though
not strictly chemical, they throw light upon some branches of the
animal economy, more closely connected with chemistry than with any
other of the sciences. He examined, in the first place, whether the
ossification of bones, and their formation and reparation, did not
follow the same law that he had assigned to the increments of trees,
and he established, by a set of experiments, that bones increase by
the ossification of layers of the periosteum, as trees do by the
hardening of their cortical layers. Bones in a soft state increase in
every direction, like the young branches of plants; but after their
induration they increase only like trees, by successive additions of
successive layers. This organization was incompatible with the opinion
of those who thought that bones increased by the addition of an earthy
matter deposited in the meshes of the organized network which forms
the texture of bones. M. Duhamel combated this opinion by an ingenious
experiment. He had been informed by Sir Hans Sloane that the bones
of young animals fed upon madder were tinged red. He conceived the
plan of feeding them alternately with food mingled with madder, and
with ordinary food. The bones of animals thus treated were found to
present alternate concentric layers of red and white, corresponding
to the different periods in which the animal had been fed with
food containing or not containing madder. When these bones are sawn
longitudinally we see the thickness of the coloured layers, greater or
less, according to the number of plates of the periosteum that have
ossified. As for the portions still soft, or susceptible of extending
themselves in every direction, such as the plates in the neighbourhood
of the marrow, the reservoir of which increases during a part of the
time that the animal continues to grow, the red colour marks equally
the progress of their ossification by coloured points more or less
extended.
This opinion was attacked by Haller, and defended by M. Fougeroux,
nephew of M. Duhamel; but it is not our business here to inquire how
far correct.
One of the most important of M. Duhamel’s papers, which will secure
his name a proud station in the annals of chemistry, is that which was
inserted in the Memoirs of the Academy for 1737, in which he shows
that the base of common salt is a true fixed alkali, different in some
respects from the alkali extracted from land plants, and known by the
name of _potash_, but similar to that obtained by the incineration of
marine plants. We are surprised that a fact so simple and elementary
was disputed by the French chemists, and rather indicated than proved
by Stahl and his followers. The conclusions of Duhamel were disputed
by Pott; but finally confirmed by Margraaf. M. Duhamel carried his
researches further, he wished to know if the difference between potash
and soda depends on the plants that produce them, or on the nature
of the soil in which they grow. He sowed kali at Denainvilliers, and
continued his experiments during a great number of years. M. Cadet, at
his request, examined the salts contained in the ashes of the kali of
Denainvilliers. He found that during the first year soda predominated
in these ashes. During the successive years the potash increased
rapidly, and at last the soda almost entirely disappeared. It was
obvious from this, that the alkalies in plants are drawn at least
chiefly from the soil in which they vegetate.
The memoirs of M. Duhamel on ether, at that time almost unknown, on
soluble tartars, and on lime, contain many facts both curious and
accurately stated; though our present knowledge of these bodies is
so much greater than his--the new facts ascertained respecting them
are so numerous and important, that the contributions of this early
experimenter, which probably had a considerable share in the success
of subsequent investigations, are now almost forgotten. Nor would many
readers bear patiently with an attempt to enumerate them.
There is a curious paper of his in the Memoirs of the Academy for
1757. In this he gives the details of a spontaneous combustion of
large pieces of cloth soaked in oil and strongly pressed. Cloth thus
prepared had often produced similar accidents. Those who were fortunate
enough to prevent them, took care to conceal the facts, partly from
ignorance of the real cause of the combustion, and partly from a fear
that if they were to state what they saw, their testimony would not
gain credit. If the combustion had not been prevented, then the public
voice would have charged those who had the care of the cloths with
culpable negligence, or even with criminal conduct. The observation
of M. Duhamel, therefore, was useful, in order to prevent such unjust
suspicions from hindering those concerned from taking the requisite
precautions. Yet, twenty years after the publication of his paper,
two accidental spontaneous combustions, in Russia, were ascribed to
treason. The empress Catharine II. alone suspected that the combustion
was spontaneous, and experiments made by her orders fully confirmed the
evidence previously advanced by the French philosopher.
One man alone would have been insufficient for all the labours
undertaken by M. Duhamel; but he had a brother who lived upon his
estate at Denainvilliers (the name of which he bore), and divided his
time between the performance of benevolent actions and studying the
operations of nature. M. Denainvilliers prosecuted in his retreat the
observations and experiments intrusted by his brother to his charge.
Thus in fact the memoirs of Duhamel exhibit the assiduous labours
of two individuals, one of whom contentedly remained unknown to the
world, satisfied with the good which he did, and the favours which he
conferred upon his country and the human race.
The works of M. Duhamel are very voluminous, and are all written with
the utmost plainness. Every thing is elementary, no previous knowledge
is taken for granted. His writings are not addressed to philosophers,
but to all those who are in quest of practical knowledge. He has been
accused of diffuseness of style, and of want of correctness; but
his style is simple and clear; and as his object was to inform, not
philosophers, but the common people, greater conciseness would have
been highly injudicious.
Neither he nor his brother ever married, but thought it better to
devote their undivided attention to study. Both were assiduous in no
ordinary degree, but the ardour of Duhamel himself continued nearly
undiminished till within a year of his death; when, though he still
attended the meetings of the academy, he no longer took the same
interest in its proceedings. On the 22d of July, 1781, just after
leaving the academy, he was struck with apoplexy, and died after
lingering twenty-two days in a state of coma.
He was without doubt one of the most eminent men of the age in which
he lived; but his merits as a chemist will chiefly be remembered
in consequence of his being the first person who demonstrated
by satisfactory evidence the peculiar nature of soda, which had
been previously confounded with potash. His merits as a vegetable
physiologist and agriculturist were of a very high order.
Peter Joseph Macquer was born at Paris, in 1718. His father, Joseph
Macquer, was descended from a noble Scottish family, which had
sacrificed its property and its country, out of attachment to the
family of the Stuarts.[183] Young Macquer made choice of medicine as
a profession, and devoted himself chiefly to chemistry, for which
he showed early a decided taste. He was admitted a member of the
Academy of Sciences in the year 1745, when he was twenty-seven years
of age. Original researches in chemistry, the composition of chemical
elementary works, and the study of the arts connected with chemistry,
occupied the whole remainder of his life.
[183] I do not know what the true name was of which Macquer is a
corruption. Ker is a Scottish name belonging to two noble families,
the Duke of Roxburgh and the Marquis of Lothian; but I am not aware of
M’Ker being a Scottish name: besides, neither of these families was
attached to the house of Stuart.
His first paper treated of the effect produced by heating a mixture of
saltpetre and white arsenic. It was previously known, that when such a
mixture is distilled nitric acid comes over tinged with a blue colour;
but nobody had thought of examining the residue of this distillation.
Macquer found it soluble in water and capable of crystallizing into a
neutral salt composed of potash (the base of saltpetre), and an acid
into which the arsenic was changed by the nitric acid communicating
oxygen to it.
Macquer found that a similar salt might be obtained with soda or
ammonia for its base. Thus he was the first person who pointed out
the existence of arsenic acid, and ascertained the properties of some
of the salts which it forms. But he made no attempt to obtain arsenic
acid in a separate state, or to determine its properties. That very
important step was reserved for Scheele, for Macquer seems to have had
no suspicion of the true nature of the salt which he had formed.
His next set of experiments was on Prussian blue. He made the first
step towards the discovery of the nature of the principle to which
that pigment owes its colour. Prussian blue had been accidentally
discovered by Diesbach, an operative chemist of Berlin, in 1710, but
the mode of producing it was kept secret till it was published in
1724, by Dr. Woodward in the Philosophical Transactions. It consisted
in mixing potash and blood together, and heating the mixture in a
covered crucible, having a small hole in the lid, till it ceased to
give out smoke. The solution of this mixture in water, when mixed with
a solution of sulphate of iron, threw down a green powder, which became
blue when treated with muriatic acid: this blue matter was _Prussian
blue_. Macquer ascertained that when Prussian blue is exposed to a
red heat its blue colour disappears, and it is converted into common
peroxide of iron. Hence he concluded that Prussian blue is a compound
of oxide of iron, and of something which is destroyed or driven off
by a red heat. He showed that this something possessed the characters
of an acid; for when Prussian blue is boiled with caustic potash it
loses its blue colour, and if the potash be boiled with successive
portions of Prussian blue, as long as it is capable of discolouring
them, it loses the characters of an acid and assumes those of a neutral
salt, and at the same time acquires the property of precipitating iron
from the solutions of the sulphate at once of a blue colour. Macquer
ascribed the green colour thrown down, by mixing the blood-lie and
sulphate of iron to the potash in the blood-lie, not being saturated
with the colouring matter of Prussian blue. Hence a portion of the iron
is thrown down in the state of Prussian blue, and another portion in
that of yellow oxide of iron: these two being mixed form a green. The
muriatic acid dissolves the yellow oxide and leaves the Prussian blue
untouched. Macquer, however, did not succeed in determining the nature
of the colouring matter; a task reserved for Scheele, whose lot it was
to take up the half-finished investigations of Macquer, and throw upon
them a new and brilliant light. Macquer thought that this colouring
matter was _phlogiston_. On that account the potash saturated with
it, which was employed by chemists to detect the presence of iron by
forming with it Prussian blue, was called _phlogisticated alkali_.
Macquer, conjointly with Baumé, subjected the grains of crude platinum,
to which the attention of chemists had been newly drawn, to experiment.
Their principle object was to examine its fusibility and ductility.
They succeeded in fusing it imperfectly, by means of a burning
mirror, and found that the grains thus treated were not destitute of
ductility. But upon the whole the experiments of these chemists threw
but little light upon the subject. Many years elapsed before chemists
were able to work this refractory metal, and to make it into vessels
fitted for the uses of the laboratory. For this important improvement,
which constitutes an era in chemistry, the chemical world was chiefly
indebted to Dr. Wollaston.
In the year 1750 M. Macquer was charged with a commission by the court.
There existed at that time in Brittany a man, the Count de la Garaie,
who, yielding to a passion for benevolence, had for forty years devoted
himself to the service of suffering humanity. He had built an hospital
by the side of a chemical laboratory: he took care of the patients in
the hospital himself; and treated them with medicines prepared in his
laboratory. Some of these were new, and, in his opinion, excellent
medicines; and he offered to sell them to government for the service of
his hospital. Macquer was charged by government with the examination of
these medicines. The project of the Count de la Garaie was to extract
the salutary parts of minerals, by a long maceration with neutral
salts. Among other things he had prepared a mercurial tincture, by a
process which lasted several months: but this tincture was merely a
solution of corrosive sublimate in spirit of wine. Such is the history
of most of those boasted secrets; sometimes they are chimerical, and
sometimes known to all the world, except to those who purchase them.
M. Macquer had the fortune to live at a time when chemistry began to
be freed from the reveries of alchymists; but methodical arrangement
was a merit still unknown to the elementary chemical books, especially
in France, where a residue of Cartesianism added to the natural
obscurity of the science, by surcharging it with pretended mechanical
explanations. Macquer was the first French chemist who gave to an
elementary treatise the same clearness, simplicity, and method,
which is to be found in the other branches of science. This was no
small merit, and undoubtedly contributed considerably to the rapid
improvement of the science which so speedily followed. His elements
of chemistry were translated into different languages, especially
into English; and long constituted the textbook employed in the
different European universities. Dr. Black recommended it for many
years in the University of Edinburgh. Indeed, it was only superseded in
consequence of the new views introduced into chemistry by Lavoisier,
which, requiring a new language to render them intelligible, naturally
superseded all the elementary chemical books which had preceded the
introduction of that language.
Macquer, during a number of years, delivered regular courses of
chemical lectures, conjointly with Baumé. In these courses he preferred
that arrangement which appeared to him to require the least preliminary
knowledge of chemistry. He described the experiments, stated the facts
with clearness and precision, and explained them in the way which
appeared to him most plausible, according to the opinions generally
received; but without placing much confidence in the accuracy of these
explanations. He thought it necessary to theorize a little, to enable
his pupils the better to connect the facts and to remember them; and to
put an end to that painful state of uncertainty which always results
from a collection of facts without any theoretical links to bind
them together. When the discoveries of Lavoisier began to shake the
foundation of the Stahlian theory, Macquer was old; and it appears from
a letter of his, published by Delametherie in the Journal de Physique,
that he was alarmed at the prophetic announcements of Lavoisier in
the academy that the reign of Phlogiston was drawing towards an end.
M. Condorcet assures us that his attachment to theory, by which he
means phlogiston, was by no means strong;[184] but his own letter to
Delametherie rather shows that this statement was not quite correct.
How, indeed, could he fail to experience an attachment to opinions
which it had been the business of his whole life to inculcate?
[184] Hist. de l’Acad. R. des Sciences, 1784, p. 24.
Macquer also published a dictionary of chemistry, which was very
successful, and which was translated into most of the European
languages. This mode of treating chemistry was well suited to a science
still in its infancy, and which did not yet constitute a complete
whole. It enabled him to discuss the different topics in succession,
and independent of each other: and thus to introduce much important
matter which could not easily have been introduced into a systematic
work on chemistry. The second edition of this dictionary was published
just at the time when the gases began to attract the attention of
scientific men; when facts began to multiply with prodigious rapidity,
and to shake the confidence of chemists in all received theories. He
acquitted himself of the difficult task of collecting and stating
these new facts with considerable success; and doubtless communicated
much new information to his countrymen: for the discoveries connected
with the gases originated, and were chiefly made, in England, from
which, on account of the revolutionary American war, there was some
difficulty of obtaining early information.
M. Hellot, who was commissioner of the counsel for dyeing, and chemist
to the porcelain manufacture, requested to have M. Macquer for an
associate. This request did much honour to Hellot, as he was conscious
that the reputation of Macquer as a chemist was superior to his
own. Macquer endeavoured, in the first place, to lay down the true
principles of the art of dyeing, as the best method of dissipating the
obscurity which still hung over it. A great part of his treatise on
the art of dyeing silk, published in the collection of the Academy of
Sciences, has these principles for its object. He gave processes also
for dyeing silk with Prussian blue, and for giving to silk, by means
of cochineal, as brilliant a scarlet colour as can be given to woollen
cloth by the same dye-stuff. He published nothing on the porcelain
manufacture, though he attended particularly to the processes, and
introduced several ameliorations. The beautiful porcelain earth at
present used at Sevre, was discovered in consequence of a premium which
he offered to any person who could point out a clay in every respect
proper for making porcelain.
Macquer passed a great part of his life with a brother, whom he
affectionately loved: after his death he devoted himself entirely to
his wife and two children, whose education he superintended. He was
rather averse to society, but conducted himself while in it with much
sweetness and affability. He was fond of tranquillity and independence.
Though his health had been injured a good many years before his death,
the calmness and serenity of his temper prevented strangers from being
aware that he was afflicted with any malady. He himself was sensible
that his strength was gradually sinking; he predicted his approaching
end to his wife, whom he thanked for the happiness which she had spread
over his life. He left orders that his body should be opened after his
decease, that the cause of his death might be discovered. He died on
the 15th of February, 1784. An ossification of the aorta, and several
calculous concretions found in the cavities of the heart, had been the
cause of the disease under which he had suffered for several years
before his death.
These four chemists, of whose lives a sketch has just been given, were
the most eminent that France ever produced belonging to the Stahlian
school of chemistry. Baron, Malouin, Rouelle senior, Tillet, Cadet,
Baumé, Sage, and several others whose names I purposely omit, likewise
cultivated chemistry, during that period, with assiduity and success;
and were each of them the authors of papers which deserve attention,
but which it would be impossible to particularize without swelling this
work into a size greatly beyond its proper limits.
Hilaire-Marin Rouelle, who was born at Caen in 1718, was, however, too
eminent a chemist to be passed over in silence. His elder brother,
William Francis, was a member of the Academy of Sciences, and
demonstrator to Macquer, who gave lectures in the Jardin du Roi. At
the death of Macquer, in 1770, Hilaire-Marin Rouelle succeeded him. He
devoted the whole of his time and money to this situation, and quite
altered the nature of the experimental course of chemistry given in the
Jardin du Roi. He was in some measure the author of the chemistry of
animal bodies, at least in France. When he published his experiments
on the salts of urine, and of blood, he had scarcely any model; and
though he committed some considerable mistakes, he ascertained several
essential and important facts, which have been since fully confirmed
by more modern experimenters. He died on the 7th of April, 1779, aged
sixty-one years. His temper was peculiar, and he was too honest and
too open for the situation in which he was placed, and for a state of
society in which every thing was carried by intrigue and finesse. This
is the reason why, in France, his reputation was lower than it ought
to have been. It accounts, too, for his never becoming a member of
the Academy of Sciences, nor of any of the other numerous academies
which at that time swarmed in France. Nothing is more common than to
find these unjust decisions raise or depress men of science far above
or far below their true standard. Romé de Lisle, the first person who
commenced the study of crystals, and placed that study in a proper
point of view, was a man of the same stamp with the younger Rouelle,
and never on that account, became a member of any academy, or acquired
that reputation during his lifetime, to which his laborious career
justly entitled him. It would be an easy, though an invidious task, to
point out various individuals, especially in France, whose reputation,
in consequence of accidental and adventitious circumstances, rose just
as much above their deserts, as those of Rouelle, and Romé de Lisle
were sunk below.