SUMMARY OF THE ALCHEMICAL DOCTRINE.--THE REPLACEMENT OF THE THREE
PRINCIPLES OF THE ALCHEMISTS BY THE SINGLE PRINCIPLE OF PHLOGISTON.
The _Sacred Art_, which had its origin and home in Egypt, was very
definitely associated with the religious rites, and the theological
teaching, recognised by the state. The Egyptian priests were initiated
into the mysteries of the divine art: and as the initiated claimed to
imitate the work of the deity, the priest was regarded by the ordinary
people as something more than a representative, as a mirror, of the
divinity. The sacred art of Egypt was transmuted into alchemy by
contact with European thought and handicrafts, and the tenets and
mysticism of the Catholic Church; and the conception of nature, which
was the result of this blending, prevailed from about the 9th until
towards the end of the 18th century.
Like its predecessor, alchemy postulated an orderly universe; but
alchemy was richer in fantastic details, more picturesquely
embroidered, more prodigal of strange fancies, than the sacred art of
Egypt.
The alchemist constructed his ordered scheme of nature on the basis of
the supposed universality of life. For him, everything lived, and the
life of things was threefold. The alchemist thought he recognised the
manifestation of life in the form, or body, of a thing, in its soul,
and in its spirit. Things might differ much in appearance, in size,
taste, smell, and other outward properties, and yet be intimately
related, because, according to the alchemist, they were produced from
the same principles, they were animated by the same soul. Things might
resemble one another closely in their outward properties and yet
differ widely in essential features, because, according to the
alchemist, they were formed from different elements, in their
spiritual properties they were unlike. The alchemists taught that the
true transformation, in alchemical language the transmutation, of one
thing into another could be effected only by spiritual means acting on
the spirit of the thing, because the transmutation consisted
essentially in raising the substance to the highest perfection whereof
it was capable; the result of this spiritual action might become
apparent in the material form of the substance. In attempting to apply
such vague conceptions as these, alchemy was obliged to use the
language which had been developed for the expression of human emotions
and desires, not only for the explanation of the facts it observed,
but also for the bare recital of these facts.
The outlook of alchemy on the world outside human beings was
essentially anthropomorphic. In the image of man, the alchemist
created his universe.
In the times when alchemy was dominant, the divine scheme of creation,
and the place given to man in that scheme, were supposed to be
thoroughly understood. Everything had its place, designed for it from
the beginning, and in that place it remained unless it were forced
from it by violent means. A great part of the business of experimental
alchemy was to discover the natural position, or condition, of each
substance; and the discovery was to be made by interpreting the facts
brought to light by observation and experiment by the aid of
hypotheses deduced from the general scheme of things which had been
formed independently of observation or experiment. Alchemy was a part
of magic; for magic interprets and corrects the knowledge gained by
the senses by the touchstone of generalisations which have been
supplied, partly by the emotions, and partly by extra-human authority,
and accepted as necessarily true.
The conception of natural order which regulates the life of the savage
is closely related to that which guided the alchemists. The essential
features of both are the notion that everything is alive, and the
persuasion that things can be radically acted on only by using life as
a factor. There is also an intimate connexion between alchemy and
witchcraft. Witches were people who were supposed to make an unlawful
use of the powers of life; alchemists were often thought to pass
beyond what is permitted to the creature, and to encroach on the
prerogative of the Creator.
The long duration of alchemy shows that it appealed to some
deep-seated want of human beings. Was not that want the necessity for
the realisation of order in the universe? Men were unwilling to wait
until patient examination of the facts of their own nature, and the
facts of nature outside themselves, might lead them to the realisation
of the interdependence of all things. They found it easier to evolve a
scheme of things from a superficial glance at themselves and their
surroundings; naturally they adopted the easier plan. Alchemy was a
part of the plan of nature produced by this method. The extraordinary
dominancy of such a scheme is testified to by the continued belief in
alchemy, although the one experiment, which seems to us to be the
crucial experiment of the system, was never accomplished. But it is
also to be remembered that the alchemists were acquainted with, and
practised, many processes which we should now describe as operations
of manufacturing and technical chemistry; and the practical usefulness
of these processes bore testimony, of the kind which convinces the
plain man, to the justness of their theories.
I have always regarded two facts as most interesting and instructive:
that the doctrine of the essential unity of all things, and the
simplicity of natural order, was accepted for centuries by many, I
think one may say, by most men, as undoubtedly a true presentation of
the divine scheme of things; and, secondly, that in more recent times
people were quite as certain of the necessary truth of the doctrine,
the exact opposite of the alchemical, that the Creator had divided his
creation into portions each of which was independent of all the
others. Both of these schemes were formed by the same method, by
introspection preceding observation; both were overthrown by the same
method, by observation and experiment proceeding hand in hand with
reasoning. In each case, the humility of science vanquished the
conceit of ignorance.
The change from alchemy to chemistry is an admirable example of the
change from a theory formed by looking inwards, and then projected on
to external facts, to a theory formed by studying facts, and then
thinking about them. This change proceeded slowly; it is not possible
to name a time when it may be said, here alchemy finishes and
chemistry begins. To adapt a saying of one of the alchemists, quoted
in a former chapter; alchemy would not easily give up its nature, and
fought for its life; but an agent was found strong enough to overcome
and kill it, and then that agent also had the power to change the
lifeless remains into a new and pure body. The agent was the accurate
and imaginative investigation of facts.
The first great step taken in the path which led from alchemy to
chemistry was the substitution of one Principle, the Principle of
Phlogiston, for the three Principles of salt, sulphur, and mercury.
This step was taken by concentrating attention and investigation, by
replacing the superficial examination of many diverse phenomena by the
more searching study of one class of occurrences. That the field of
study should be widened, it was necessary that it should first be
narrowed.
Lead, tin, iron, or copper is calcined. The prominent and striking
feature of these events is the disappearance of the metal, and the
formation of something very unlike it. But the original metal is
restored by a second process, which is like the first because it also
is a calcination, but seems to differ from the first operation in that
the burnt metal is calcined with another substance, with grains of
wheat or powdered charcoal. Led thereto by their theory that
destruction must precede re-vivification, death must come before
resurrection, the alchemists confined their attention to one feature
common to all calcinations of metals, and gave a superficial
description of these occurrences by classing them together as
processes of mortification. Sulphur, wood, wax, oil, and many other
things are easily burned: the alchemists said, these things also
undergo mortification, they too are killed; but, as "man can restore
that which man has destroyed," it must be possible to restore to life
the thing which has been mortified. The burnt sulphur, wood, wax, or
oil, is not really dead, the alchemists argued; to use the allegory of
Paracelsus, they are like young lions which are born dead, and are
brought to life by the roaring of their parents: if we make a
sufficiently loud noise, if we use the proper means, we shall bring
life into what seems to be dead material. As it is the roaring of the
parents of the young lions which alone can cause the still-born cubs
to live, so it is only by the spiritual agency of life, proceeded the
alchemical argument, that life can be brought into the mortified
sulphur, wood, wax, and oil.
The alchemical explanation was superficial, theoretical, in the wrong
meaning of that word, and unworkable. It was superficial because it
overlooked the fact that the primary calcination, the mortification,
of the metals, and the other substances, was effected in the air, that
is to say, in contact with something different from the thing which
was calcined; the explanation was of the kind which people call
theoretical, when they wish to condemn an explanation and put it out
of court, because it was merely a re-statement of the facts in the
language of a theory which had not been deduced from the facts
themselves, or from facts like those to be explained, but from what
were supposed to be facts without proper investigation, and, if facts,
were of a totally different kind from those to which the explanation
applied; and lastly, the explanation was unworkable, because it
suggested no method whereby its accuracy could be tested, no definite
line of investigation which might be pursued.
That great naturalist, the Honourable Robert Boyle (born in 1626, died
in 1691), very perseveringly besought those who examined processes of
calcination to pay heed to the action of everything which might take
part in the processes. He was especially desirous they should consider
what part the air might play in calcinations; he spoke of the air as a
"menstruum or additament," and said that, in such operations as
calcination, "We may well take the freedom to examine ... whether
there intervene not a coalition of the parts of the body wrought upon
with those of the menstruum, whereby the produced concrete may be
judged to result from the union of both."
It was by examining the part played by the air in processes of
calcination and burning that men at last became able to give
approximately complete descriptions of these processes.
Boyle recognised that the air is not a simple or elementary substance;
he spoke of it as "a confused aggregate of effluviums from such
differing bodies, that, though they all agree in constituting by their
minuteness and various motions one great mass of fluid matter, yet
perhaps there is scarce a more heterogeneous body in the world."
Clement of Alexandria who lived in the end of the 2nd, and the early
part of the 3rd, century A.D., seems to have regarded the air as
playing a very important part in combustions; he said--"Airs are
divided into two categories; an air for the divine flame, which is the
soul; and a material air which is the nourisher of sensible fire, and
the basis of combustible matter." Sentences like that I have just
quoted are found here and there in the writings of the earlier and
later alchemists; now and again we also find statements which may be
interpreted, in the light of the fuller knowledge we now have, as
indicating at least suspicions that the atmosphere is a mixture of
different kinds of air, and that only some of these take part in
calcining and burning operations. Those suspicions were confirmed by
experiments on the calcination of metals and other substances,
conducted in the 17th century by Jean Rey a French physician, and by
John Mayow of Oxford. But these observations and the conclusions
founded on them, did not bear much fruit until the time of Lavoisier,
that is, towards the close of the 18th century. They were overshadowed
and put aside by the work of Stahl (1660-1724). Some of the alchemists
of the 14th, 15th and 16th centuries taught that combustion and
calcination are processes wherein _the igneous principle_ is
destroyed, using the word "destroyed" in its alchemical meaning. This
description of processes of burning was much more in keeping with the
ideas of the time than that given by Boyle, Rey and Mayow. It was
adopted by Stahl, and made the basis of a general theory of those
changes wherein one substance disappears and another, or others, very
unlike it, are produced.
That he might bring into one point of view, and compare the various
changes effected by the agency of fire, Stahl invented a new
Principle, which he named _Phlogiston_, and constructed an hypothesis
which is generally known as the phlogistic theory. He explained, and
applied, this hypothesis in various books, especially in one published
at Halle in 1717.
Stahl observed that many substances which differed much from one
another in various respects were alike in one respect; they were all
combustible. All the combustible substances, he argued, must contain a
common principle; he named this supposed principle, _phlogiston_ (from
the Greek word _phlogistos_ = burnt, or set on fire). Stahl said that
the phlogiston of a combustible thing escapes as the substance burns,
and, becoming apparent to the senses, is named fire or flame. The
phlogiston in a combustible substance was supposed to be so
intimately associated with something else that our senses cannot
perceive it; nevertheless, the theory said, it is there; we can see
only the escaping phlogiston, we can perceive only the phlogiston
which is set free from its combination with other things. The theory
thought of phlogiston as imprisoned in the thing which can be burnt,
and as itself forming part of the prison; that the prisoner should be
set free, the walls of the prison had to be removed; the freeing of
the prisoner destroyed the prison. As escaping, or free, phlogiston
was called fire, or flame, so the phlogiston in a combustible
substance was sometimes called combined fire, or flame in the state of
combination. A peculiarity of the strange thing called phlogiston was
that it preferred to be concealed in something, hidden, imprisoned,
combined; free phlogiston* was supposed to be always ready to become
combined phlogiston.
*Transcriber's Note: Original "phlogstion".
The phlogistic theory said that what remains when a substance has been
burnt is the original substance deprived of phlogiston; and,
therefore, to restore the phlogiston to the product of burning is to
re-form the combustible substance. But how is such a restoration of
phlogiston to be accomplished? Evidently by heating the burnt thing
with something which is very ready to burn. Because, according to the
theory, everything which can be burnt contains phlogiston, the more
ready a substance is to burn the richer it is in phlogiston; burning
is the outrush of phlogiston, phlogiston prefers to be combined with
something; therefore, if you mix what remains after burning, with
something which is very combustible, and heat the mixture, you are
bringing the burnt matter under conditions which are very favourable
for the reception of phlogiston by it, for you are bringing it into
intimate contact with something from which freedom-hating phlogiston
is being forced to escape.
Charcoal, sulphur, phosphorus, oils and fats are easily burnt; these
substances were, therefore, chosen for the purpose of changing things
which had been burnt into things which could again be burnt; these,
and a few other substances like these, were classed together, and
called _phlogisticating agents_.
Very many of the substances which were dealt with by the experimenters
of the last quarter of the 17th, and the first half of the 18th,
century, were either substances which could be burned, or those which
had been produced by burning; hence the phlogistic theory brought into
one point of view, compared, and emphasised the similarities between,
a great many things which had not been thought of as connected before
that theory was promulgated. Moreover, the theory asserted that all
combustible, or incinerable, things are composed of phlogiston, and
another principle, or, as was often said, another element, which is
different in different kinds of combustible substances. The metals,
for instance, were said to be composed of phlogiston and an earthy
principle or element, which was somewhat different in different
metals. The phlogisteans taught that the earthy principle of a metal
remains in the form of ash, cinders, or calx, when the metal is
calcined, or, as they expressed it, when the metal is deprived of its
phlogiston.
The phlogistic theory savoured of alchemy; it postulated an undefined,
undefinable, intangible Principle; it said that all combustible
substances are formed by the union of this Principle with another,
which is sometimes of an earthy character, sometimes of a fatty
nature, sometimes highly volatile in habit. Nevertheless, the theory
of Stahl was a step away from purely alchemical conceptions towards
the accurate description of a very important class of changes. The
principle of phlogiston could be recognised by the senses as it was in
the act of escaping from a substance; and the other principle of
combustible things was scarcely a Principle in the alchemical sense,
for, in the case of metals at any rate, it remained when the things
which had contained it were burnt, and could be seen, handled, and
weighed. To say that metals are composed of phlogiston and an earthy
substance, was to express facts in such a language that the expression
might be made the basis of experimental inquiry; it was very different
from the assertion that metals are produced by the spiritual actions
of the three Principles, salt, mercury and sulphur, the first of which
is not salt, the second is not mercury, and the third is not sulphur.
The followers of Stahl often spoke of metals as composed of phlogiston
and an _element_ of an earthy character; this expression also was an
advance, from the hazy notion of _Element_ in purely alchemical
writings, towards accuracy and fulness of description. An element was
now something which could he seen and experimented with; it was no
longer a semi-spiritual existence which could not be grasped by the
senses.
The phlogistic theory regarded the calcination of a metal as the
separation of it into two things, unlike the metal, and unlike each
other; one of these things was phlogiston, the other was an earth-like
residue. The theory thought of the re-formation of a metal from its
calx, that is, the earthy substance which remains after combustion, as
the combination of two things to produce one, apparently homogeneous,
substance. Metals appeared to the phlogisteans, as they appeared to
the alchemists, to be composite substances. Processes of burning were
regarded by alchemists and phlogisteans alike, as processes of
simplification.
The fact had been noticed and recorded, during the middle ages, that
the earth-like matter which remains when a metal is calcined is
heavier than the metal itself. From this fact, modern investigators of
natural phenomena would draw the conclusion, that calcination of a
metal is an addition of something to the metal, not a separation of
the metal into different things. It seems impossible to us that a
substance should be separated into portions, and one of these parts
should weigh as much as, or more than, the whole.
The exact investigation of material changes called chemistry rests on
the statement that _mass_, and mass is practically measured by
_weight_, is the one property of what we call matter, the
determination whereof enables us to decide whether a change is a
combination, or coalescence, of different things, or a separation of
one thing into parts. That any part of a material system can be
removed without the weight of the portion which remains being less
than the original weight of the whole system, is unthinkable, in the
present state of our knowledge of material changes.
But in the 17th century, and throughout most of the 18th, only a few
of those who examined changes in the properties of substances paid
heed to changes of weight; they had not realised the importance of the
property of mass, as measured by weight. The convinced upholder of the
phlogistic theory had two answers to the argument, that, because the
earth-like product of the calcination of a metal weighs more than the
metal itself, therefore the metal cannot have lost something in the
process; for, if one portion of what is taken away weighs more than
the metal from which it has been separated, it is evident that the
weight of the two portions into which the metal is said to have been
divided must be considerably greater than the weight of the undivided
metal. The upholders of the theory sometimes met the argument by
saying, "Of course the calx weighs more than the metal, because
phlogiston tends to lighten a body which contains it; and therefore
the body weighs more after it has lost phlogiston than it did when the
phlogiston formed part of it;" sometimes, and more often, their answer
was--"loss or gain of weight is an accident, the essential thing is
change of qualities."
If the argument against the separation of a metal into two
constituents, by calcination, were answered to-day as it was answered
by the upholders of the phlogistic theory, in the middle of the 18th
century, the answers would justly be considered inconsequent and
ridiculous. But it does not follow that the statements were either
far-fetched or absurd at the time they were made. They were expressed
in the phraseology of the time; a phraseology, it is true, sadly
lacking in consistency, clearness, and appropriateness, but the only
language then available for the description of such changes as those
which happen when metals are calcined. One might suppose that it must
always have sounded ridiculous to say that the weight of a thing can
be decreased by adding something to it, that part of a thing weighs
more than the whole of it. But the absurdity disappears if it can be
admitted that mass, which is measured by weight, may be a property
like colour, or taste, or smell; for the colour, taste, or smell of a
thing may certainly be made less by adding something else, and the
colour, taste, or smell of a thing may also be increased by adding
something else. If we did not know that what we call _quantity of
substance_ is measured by the property named _mass_, we might very
well accept the proposition that the entrance of phlogiston into a
substance decreases the quantity, hence the mass, and, therefore, the
weight, of the substance.
Although Stahl and his followers were emerging from the trammels of
alchemy, they were still bound by many of the conceptions of that
scheme of nature. We have learned, in previous chapters, that the
central idea of alchemy was expressed in the saying: "Matter must be
deprived of its properties in order to draw out its soul." The
properties of substances are everything to the modern chemist--indeed,
such words as iron, copper, water, and gold are to him merely
convenient expressions for certain definable groups of properties--but
the phlogisteans regarded the properties of things, including mass, as
of secondary importance; they were still trying to get beneath the
properties of a thing, to its hypothetical essence, or substance.
Looking back, we cannot think of phlogiston as a substance, or as a
thing, in the modern meanings of these terms as they are used in
natural science. Nowadays we think, we are obliged to think, of the
sum of the quantities of all the things in the universe as unchanging,
and unchangeable by any agency whereof we have definite knowledge. The
meaning we give to the word _thing_ rests upon the acceptance of this
hypothesis. But the terms _substance_, _thing_, _properties_ were used
very vaguely a couple of centuries ago; and it would be truly absurd
to carry back to that time the meanings which we give to these terms
to-day, and then to brand as ridiculous the attempts of the men who
studied, then, the same problems which we study now, to express the
results of their study in generalisations which employed the terms in
question, in what seems to us a loose, vague, and inexact manner.
By asserting, and to some extent experimentally proving, the existence
of one principle in many apparently very different substances (or, as
would be said to-day, one property common to many substances), the
phlogistic theory acted as a very useful means for collecting, and
placing in a favourable position for closer inspection, many
substances which would probably have remained scattered and detached
from one another had this theory not been constructed. A single
assumption was made, that all combustible substances are alike in one
respect, namely, in containing combined fire, or phlogiston; by the
help of this assumption, the theory of phlogiston emphasised the
fundamental similarity between all processes of combustion. The theory
of phlogiston was extraordinarily simple, compared with the alchemical
vagaries which preceded it. Hoefer says, in his _Histoire de la
Chimie_, "If it is true that simplicity is the distinctive character
of verity, never was a theory so true as that of Stahl."
The phlogistic theory did more than serve as a means for bringing
together many apparently disconnected facts. By concentrating the
attention of the students of material changes on one class of events,
and giving descriptions of these events without using either of the
four alchemical Elements, or the three Principles, Stahl, and those
who followed him, did an immense service to the advancement of clear
thinking about natural occurrences. The principle of phlogiston was
more tangible, and more readily used, than the Salt, Sulphur, and
Mercury of the alchemists; and to accustom people to speak of the
material substance which remained when a metal, or other combustible
substance, was calcined or burnt, as one of the _elements_ of the
thing which had been changed, prepared the way for the chemical
conception of an element as a definite substance with certain definite
properties.
In addition to these advantages, the phlogistic theory was based on
experiments, and led to experiments, the results of which proved that
the capacity to undergo combustion might be conveyed to an
incombustible substance, by causing it to react with some other
substance, itself combustible, under definite conditions. The theory
thus prepared the way for the representation of a chemical change as
an interaction between definite kinds of substances, marked by precise
alterations both of properties and composition.
The great fault of the theory of phlogiston, considered as a general
conception which brings many facts into one point of view, and leads
the way to new and exact knowledge, was its looseness, its
flexibility. It was very easy to make use of the theory in a broad and
general way; by stretching it here, and modifying it there, it seemed
to cover all the facts concerning combustion and calcination which
were discovered during two generations after the publication of
Stahl's books. But many of the subsidiary hypotheses which were
required to make the theory cover the new facts were contradictory, or
at any rate seemed to be contradictory, of the primary assumptions of
the theory. The addition of this ancillary machinery burdened the
mechanism of the theory, threw it out of order, and finally made it
unworkable. The phlogistic theory was destroyed by its own
cumbersomeness.
A scientific theory never lasts long if its fundamental assumptions
are stated so loosely that they may be easily modified, expanded,
contracted, and adjusted to meet the requirements of newly discovered
facts. It is true that the theories which have been of the greatest
service in science, as summaries of the relations between established
facts, and suggestions of lines of investigation, have been stated in
terms whose full meaning has gradually unfolded itself. But the
foundations of these theories have been at once so rigidly defined and
clearly stated as to be incapable of essential modification, and so
full of meaning and widely applicable as to cover large classes of
facts which were unknown when the theories were constructed. Of the
founders of the lasting and expansible theories of natural science, it
may be said, that "thoughts beyond their thoughts to those high bards
were given."