CHAPTER III.

PROGRESS OF SCIENTIFIC CHEMISTRY IN FRANCE.

I have already given an account of the state of chemistry in France,

during the earlier part of the eighteenth century, as it was cultivated

by the Stahlian school. But the new aspect which chemistry put on in

Britain in consequence of the discoveries of Black, Cavendish, and

Priestley, and the conspicuous part which the gases newly made known

was likely to take in the future progress of the science, drew to

the study of chemistry, sometime after the middle of the eighteenth

century, a man who was destined to produce a complete revolution, and

to introduce the same precision, and the same accuracy of deductive

reasoning which distinguishes the other branches of natural science.

This man was Lavoisier.

Antoine Laurent Lavoisier was born in Paris on the 26th of August,

1743. His father being a man of opulence spared no expense on his

education. His taste for the physical sciences was early displayed, and

the progress which he made in them was uncommonly rapid. In the year

1764 a prize was offered by the French government for the best and most

economical method of lighting the streets of an extensive city. Young

Lavoisier, though at that time only twenty-one years of age, drew up a

memoir on the subject which obtained the gold medal. This essay was

inserted in the Memoirs of the French Academy of Sciences, for 1768. It

was during that year, when he was only twenty-five years of age that

he became a member of that scientific body. By this time he was become

fully conscious of his own strength; but he hesitated for some time to

which of the sciences he should devote his attention. He tried pretty

early to determine, experimentally, some chemical questions which at

that time drew the attention of practical chemists. For example: an

elaborate paper of his appeared in the Memoirs of the French Academy,

for 1768, on the composition of _gypsum_--a point at that time not

settled; but which Lavoisier proved, as Margraaf had done before him,

to be a compound of sulphuric acid and lime. In the Memoirs of the

Academy, for 1770, two papers of his appeared, the object of which

was to determine whether water could, as Margraaf had pretended, be

converted into _silica_ by long-continued digestion in glass vessels.

Lavoisier found, as Margraaf stated, that when water is digested for a

long time in a glass retort, a little silica makes its appearance; but

he showed that this silica was wholly derived from the retort. Glass,

it is well known, is a compound of silica and a fixed alkali. When

water is long digested on it the glass is slightly corroded, a little

alkali is dissolved in the water and a little silica separated in the

form of a powder.

He turned a good deal of his attention also to geology, and made

repeated journeys with Guettard into almost every part of France.

The object in view was an accurate description of the mineralogical

structure of France--an object accomplished to a considerable extent by

the indefatigable exertions of Guettard, who published different papers

on the subject in the Memoirs of the French Academy, accompanied with

geological maps; which were at that time rare.

The mathematical sciences also engrossed a considerable share of his

attention. In short he displayed no great predilection for one study

more than another, but seemed to grasp at every branch of science with

equal avidity. While in this state of suspension he became acquainted

with the new and unexpected discoveries of Black, Cavendish, and

Priestley, respecting the gases. This opened a new creation to his

view, and finally determined him to devote himself to scientific

chemistry.

In the year 1774 he published a volume under the title of "Essays

Physical and Chemical." It was divided into two parts. The first part

contained an historical detail of every thing that had been done on

the subject of airs, from the time of Paracelsus down to the year

1774. We have the opinions and experiments of Van Helmont, Boyle,

Hales, Boerhaave, Stahl, Venel, Saluces, Black, Macbride, Cavendish,

and Priestley. We have the history of Meyer's acidum pingue, and the

controversy carried on in Germany, between Jacquin on the one hand, and

Crans and Smeth on the ether.

In the second part Lavoisier relates his own experiments upon gaseous

substances. In the first four chapters he shows the truth of Dr.

Black's theory of fixed air. In the 4th and 5th chapters he proves that

when metallic calces are reduced, by heating them with charcoal, an

elastic fluid is evolved, precisely of the same nature with carbonic

acid gas. In the 6th chapter he shows that when metals are calcined

their weight increases, and that a portion of air equal to their

increase in weight is absorbed from the surrounding atmosphere. He

observed that in a given bulk of air calcination goes on to a certain

point and then stops altogether, and that air in which metals have

been calcined does not support combustion so well as it did before any

such process was performed in it. He also burned phosphorus in a given

volume of air, observed the diminution of volume of the air and the

increase of the weight of the phosphorus.

Nothing in these essays indicates the smallest suspicion that air

was a mixture of two distinct fluids, and that only one of them was

concerned in combustion and calcination; although this had been already

deduced by Scheele from his own experiments, and though Priestley had

already discovered the existence and peculiar properties of oxygen

gas. It is obvious, however, that Lavoisier was on the way to make

these discoveries, and had neither Scheele nor Priestley been fortunate

enough to hit upon oxygen gas, it is exceedingly likely that he would

himself have been able to have made that discovery.

Dr. Priestley, however, happened to be in Paris towards the end of

1774, and exhibited to Lavoisier, in his own laboratory in Paris,

the method of procuring oxygen gas from red oxide of mercury. This

discovery altered all his views, and speedily suggested not only

the nature of atmospheric air, but also what happens during the

calcination of metals and the combustion of burning bodies in general.

These opinions when once formed he prosecuted with unwearied industry

for more than twelve years, and after a vast number of experiments,

conducted with a degree of precision hitherto unattempted in chemical

investigations, he boldly undertook to disprove the existence of

phlogiston altogether, and to explain all the phenomena hitherto

supposed to depend upon that principle by the simple combination or

separation of oxygen from bodies.

In these opinions he had for some years no coadjutors or followers,

till, in 1785, Berthollet at a meeting of the Academy of Sciences,

declared himself a convert. He was followed by M. Fourcroy, and soon

after Guyton de Morveau, who was at that time the editor of the

chemical department of the Encyclopédie Méthodique, was invited to

Paris by Lavoisier and prevailed upon to join the same party. This was

followed by a pretty vigorous controversy, in which Lavoisier and his

associates gained a signal victory.

Lavoisier, after Buffon and Tillet, was treasurer to the academy,

into the accounts of which he introduced both economy and order. He

was consulted by the National Convention on the most eligible means

of improving the manufacture of assignats, and of augmenting the

difficulty of forging them. He turned his attention also to political

economy, and between 1778 and 1785 he allotted 240 arpents in the

Vendomois to experimental agriculture, and increased the ordinary

produce by one-half. In 1791 the Constituent Assembly invited him

to draw up a plan for rendering more simple the collection of the

taxes, which produced an excellent report, printed under the title of

"Territorial Riches of France."

In 1776 he was employed by Turgot to inspect the manufactory of

gunpowder; which he made to carry 120 toises, instead of 90. It is

pretty generally known, that during the war of the American revolution,

the French gunpowder was much superior to the British; but it is

perhaps not so generally understood, that for this superiority the

French government were indebted to the abilities of Lavoisier. During

the war of the French revolution, the quality of the powder of the two

nations was reversed; the English being considerably superior to that

of the French, and capable of carrying further. This was put to the

test in a very remarkable way at Cadiz.

During the horrors of the dictatorship of Robespierre, Lavoisier began

to suspect that he would be stripped of his property, and informed

Lalande that he was extremely willing to work for his subsistence. It

was supposed that he meant to pursue the profession of an apothecary,

as most congenial to his studies: but he was accused, along with the

other _farmers-general_, of defrauding the revenue, and thrown into

prison. During that sanguinary period imprisonment and condemnation

were synonymous terms. Accordingly, on the 8th of May, 1794, he

suffered on the scaffold, with twenty-eight farmers-general, at the

early age of fifty-one. It has been, alleged that Fourcroy, who at that

time possessed considerable influence, might have saved him had he been

disposed to have exerted himself. But this accusation has never been

supported by any evidence. Lavoisier was a man of too much eminence

to be overlooked, and no accused person at that time could be saved

unless he was forgotten. A paper was presented to the tribunal, drawn

up by M. Hallé, giving a catalogue of the works, and a recapitulation

of the merits of Lavoisier; but it was thrown aside without even being

read, and M. Hallé had reason to congratulate himself that his useless

attempts to save Lavoisier did not terminate in his own destruction.

Lavoisier was tall, and possessed a countenance full of benignity,

through which his genius shone forth conspicuous. He was mild, humane,

sociable, obliging, and he displayed an incredible degree of activity.

His influence was great, on account of his fortune, his reputation,

and the place which he held in the treasury; but all the use which

he made of it was to do good. His wife, whom he married in 1771,

was Marie-Anna-Pierette-Paulze, daughter of a farmer-general, who

was put to death at the same time with her husband; she herself was

imprisoned, but saved by the fortunate destruction of the dictator

himself, together with his abettors. It would appear that she was able

to save a considerable part of her husband's fortune: she afterwards

married Count Rumford, whom she survived.

Besides his volume of Physical and Chemical Essays, and his Elements of

Chemistry, published in 1789, Lavoisier was the author of no fewer than

sixty memoirs, which were published in the volumes of the Academy of

Sciences, from 1772, to 1788, or in other periodical works of the time.

I shall take a short review of the most important of these memoirs,

dividing them into two parts: I. Those that are not connected with his

peculiar chemical theory; II. Those which were intended to disprove the

existence of phlogiston, and establish the antiphlogistic theory.

I. I have already mentioned his paper on gypsum, published in the

Memoirs of the Academy, for 1768. He proves, by very decisive

experiments, that this salt is a compound of sulphuric acid, lime,

and water. But this had been already done by Margraaf, in a paper

inserted into the Memoirs of the Berlin Academy, for 1750, entitled

"An Examination of the constituent parts of the Stones that become

luminous." The most remarkable circumstance attending this paper is,

that an interval of eighteen years should elapse without Lavoisier's

having any knowledge of this important paper of Margraaf; yet he quotes

Pott and Cronstedt, who had written on the same subject later than

Margraaf, at least Cronstedt. What makes this still more singular and

unaccountable is, that a French translation of Margraaf's Opuscula had

been published in Paris, in the year 1762. That a man in Lavoisier's

circumstances, who, as appears from his paper, had paid considerable

attention to chemistry, should not have perused the writings of one

of the most eminent chemists that had ever existed, when they were

completely within his power, constitutes, I think, one of the most

extraordinary phenomena in the history of science.

2. If a want of historical knowledge appears conspicuous in Lavoisier's

first chemical paper, the same remark cannot be applied to his second

paper, "On the Nature of Water, and the Experiments by which it has

been attempted to prove the possibility of changing it into Earth,"

which was inserted in the Memoirs of the French Academy, for 1770. This

memoir is divided into two parts. In the first he gives a history of

the progress of opinions on the subject, beginning with Van Helmont's

celebrated experiment on the willow; then relating those of Boyle,

Triewald, Miller, Eller, Gleditch, Bonnet, Kraft, Alston, Wallerius,

Hales, Duhamel, Stahl, Boerhaave, Geoffroy, Margraaf, and Le Roy. This

first part is interesting, in an historical point of view, and gives

a very complete account of the progress of opinions upon the subject

from the very first dawn of scientific chemistry down to his own time.

There is, it is true, a remarkable difference between the opinions

of his predecessors respecting the conversion of water into earth,

and the experiments of Margraaf on the composition of _selenite_. The

former were inaccurate, and were recorded by him that they might be

refuted; but the experiments of Margraaf were accurate, and of the

same nature with his own. The second part of this memoir contains his

own experiments, made with much precision, which went to show that

the earth was derived from the retort in which the experiments of

Margraaf were made, and that we have no proof whatever that water may

be converted into earth.

But these experiments of Lavoisier, though they completely disproved

the inferences that Margraaf drew from his observations, by no means

demonstrated that water might not be converted into different animal

and vegetable substances by the processes of digestion. Indeed there

can be no doubt that this is the case, and that the oxygen and hydrogen

of which it is composed, enter into the composition of by far the

greater number of animal and vegetable bodies produced by the action

of the functions of living animals and vegetables. We have no evidence

that the carbon, another great constituent of vegetable bodies,

and the carbon and azote which constitute so great a proportion of

animal substances, have their origin from water. They are probably

derived from the food of plants and animals, and from the atmosphere

which surrounds them, and which contains both of these principles in

abundance.

Whether the silica, lime, alumina, magnesia, and iron, that exist in

small quantity in plants, be derived from water and the atmosphere, is

a question which we are still unable to answer. But the experiments

of Schrader, which gained the prize offered by the Berlin Academy,

in the year 1800, for the best essay on the following subject: _To

determine the earthy constituents of the different kinds of corn, and

to ascertain whether these earthy parts are formed by the processes of

vegetation_, show at least that we cannot account for their production

in any other way. Schrader analyzed the seeds of wheat, rye, barley,

and oats, and ascertained the quantity of earthy matter which each

contained. He then planted these different seeds in flowers of sulphur,

and in oxides of antimony and zinc, watering them regularly with

distilled water. They vegetated very well. He then dried the plants,

and analyzed what had been the produce of a given weight of seed, and

he found that the earthy matter in each was greater than it had been in

the seeds from which they sprung. Now as the sulphur and oxides of zinc

and antimony could furnish no earthy matter, no other source remains

but the water with which the plants were fed, and the atmosphere

with which they were surrounded. It may be said, indeed, that earthy

matter is always floating about in the atmosphere, and that in this

way they may have obtained all the addition of these principles which

they contained. This is an objection not easily obviated, and yet it

would require to be obviated before the question can be considered as

answered.

3. Lavoisier's next paper, inserted in the Memoirs of the Academy, for

1771, was entitled "Calculations and Observations on the Project of

the establishment of a Steam-engine to supply Paris with Water." This

memoir, though long and valuable, not being strictly speaking chemical,

I shall pass over. Mr. Watt's improvements seem to have been unknown

to Lavoisier, indeed as his patent was only taken out in 1769, and as

several years elapsed before the merits of his new steam-engine became

generally known, Lavoisier's acquaintance with it in 1771 could hardly

be expected.

4. In 1772 we find a paper, by Lavoisier, in the Memoirs of the

Academy, "On the Use of Spirit of Wine in the analysis of Mineral

Waters." He shows how the earthy muriates may be separated from the

sulphates by digesting the mixed mass in alcohol. This process no doubt

facilitates the separation of the salts from each other: but it is

doubtful whether the method does not occasion new inaccuracies that

more than compensate the facility of such separations. When different

salts are dissolved in water in small quantities, it may very well

happen that they do not decompose each other, being at too great a

distance from each other to come within the sphere of mutual action.

Thus it is possible that sulphate of soda and muriate of lime may exist

together in the same water. But if we concentrate this water very

much, and still more, if we evaporate to dryness, the two salts will

gradually come into the sphere of mutual action, a double decomposition

will take place, and there will be formed sulphate of lime and common

salt. If upon the dry residue we pour as much distilled water as was

driven off by the evaporation, we shall not be able to dissolve the

saline matter deposited; a portion of sulphate of lime will remain

in the state of a powder. Yet before the evaporation, all the saline

contents of the water were in solution, and they continued in solution

till the water was very much concentrated. This is sufficient to show

that the nature of the salts was altered by the evaporation. If we

digest the dry residue in spirit of wine, we may dissolve a portion of

muriate of lime, if the quantity of that salt in the original water was

greater than the sulphate of soda was capable of decomposing: but if

the quantity was just what the sulphate of soda could decompose, the

alcohol will dissolve nothing, if it be strong enough, or nothing but a

little common salt, if its specific gravity was above 0·820. We cannot,

therefore, depend upon the salts which we obtain after evaporating a

mineral water to dryness, being the same as those which existed in the

mineral water itself. The nature of the salts must always be determined

some other way.

5. In the Memoirs of the Academy, for 1772 (published in 1776), are

inserted two elaborate papers of Lavoisier, on the combustion of the

diamond. The combustibility of the diamond was suspected by Newton,

from its great refractive power. His suspicion was confirmed in

1694, by Cosmo III., Grand Duke of Tuscany, who employed Averani and

Targioni to try the effect of powerful burning-glasses upon diamonds.

They were completely dissipated by the heat. Many years after, the

Emperor Francis I. caused various diamonds to be exposed to the heat

of furnaces. They also were dissipated, without leaving any trace

behind them. M. Darcet, professor of chemistry at the Royal College

of Paris, being employed with Count Lauragais in a set of experiments

on the manufacture of porcelain, took the opportunity of trying what

effect the intense heat of the porcelain furnaces produced upon

various bodies. Diamonds were not forgotten. He found that they were

completely dissipated by the heat of the furnace, without leaving any

traces behind them. Darcet found that a violent heat was not necessary

to volatilize diamonds. The heat of an ordinary furnace was quite

sufficient. In 1771 a diamond, belonging to M. Godefroi Villetaneuse,

was exposed to a strong heat by Macquer. It was placed upon a cupel,

and raised to a temperature high enough to melt copper. It was observed

to be surrounded with a low red flame, and to be more intensely red

than the cupel. In short, it exhibited unequivocal marks of undergoing

real combustion.

These experiments were soon after repeated by Lavoisier before a

large company of men of rank and science. The real combustion of the

diamond was established beyond doubt; and it was ascertained also,

that if it be completely excluded from the air, it may be exposed to

any temperature that can be raised in a furnace without undergoing

any alteration. Hence it is clear that the diamond is not a volatile

substance, and that it is dissipated by heat, not by being volatilized,

but by being burnt.

The object of Lavoisier in his experiments was to determine the nature

of the substance into which the diamond was converted by burning. In

the first part he gives as usual a history of every thing which had

been done previous to his own experiments on the combustion of the

diamond. In the second part we have the result of his own experiments

upon the same subject. He placed diamonds on porcelain supports in

glass jars standing inverted over water and over mercury; and filled

with common air and with oxygen gas.[4]

[4] The reader will bear in mind that though the memoir was inserted

in the Mem. de l'Acad., for 1772, it was in fact published in 1776,

and the experiments were made in 1775 and 1776.

The diamonds were consumed by means of burning-glasses. No _water_ or

_smoke_ or _soot_ made their appearance, and no alteration took place

on the bulk of the air when the experiments were made over mercury.

When they were made over water, the bulk of the air was somewhat

diminished. It was obvious from this that diamond when burnt in air or

oxygen gas, is converted into a gaseous substance, which is absorbed by

water. On exposing air in which diamond had been burnt, to lime-water,

a portion of it was absorbed, and the lime-water was rendered milky.

From this it became evident, that when diamond is burnt, _carbonic

acid_ is formed, and this was the only product of the combustion that

could be discovered.

Lavoisier made similar experiments with charcoal, burning it in air and

oxygen gas, by means of a burning-glass. The results were the same:

carbonic acid gas was formed in abundance, and nothing else. These

experiments might have been employed to support and confirm Lavoisier's

peculiar theory, and they were employed by him for that purpose

afterwards. But when they were originally published, no such intention

appeared evident; though doubtless he entertained it.

6. In the second volume of the Journal de Physique, for 1772, there

is a short paper by Lavoisier on the conversion of water into ice. M.

Desmarets had given the academy an account of Dr. Black's experiments,

to determine the latent heat of water. This induced Lavoisier to relate

his experiments on the same subject. He does not inform us whether

they were made in consequence of his having become acquainted with Dr.

Black's theory, though there can be no doubt that this must have been

the case. The experiments related in this short paper are not of much

consequence. But I have thought it worth while to notice it because it

authenticates a date at which Lavoisier was acquainted with Dr. Black's

theory of latent heat.

7. In the third volume of the Journal de Physique, there is an account

of a set of experiments made by Bourdelin, Malouin, Macquer, Cadet,

Lavoisier, and Baumé on the _white-lead ore_ of Pullowen. The report

is drawn up by Baumé. The nature of the ore is not made out by these

experiments. They were mostly made in the dry way, and were chiefly

intended to show that the ore was not a chloride of lead. It was most

likely a phosphate of lead.

8. In the Memoirs of the Academy, for 1774, we have the experiments of

Trudaine, de Montigny, Macquer, Cadet, Lavoisier, and Brisson, with

the great burning-glass of M. Trudaine. The results obtained cannot be

easily abridged, and are not of sufficient importance to be given in

detail.

9. Analysis of some waters brought from Italy by M. Cassini, junior.

This short paper appeared in the Memoirs of the Academy, for 1777. The

waters in question were brought from alum-pits, and were found to

contain alum and sulphate of iron.

10. In the same volume of the Memoirs of the Academy, appeared his

paper "On the Ash employed by the Saltpetre-makers of Paris, and on its

use in the Manufacture of Saltpetre." This is a curious and valuable

paper; but not sufficiently important to induce me to give an abstract

of it here.

11. In the Memoirs of the Academy, for 1777, appeared an elaborate

paper, by Lavoisier, "On the Combination of the matter of Fire, with

Evaporable Fluids, and the Formation of Elastic aeriform Fluids." In

this paper he adopts precisely the same theory as Dr. Black had long

before established. It is remarkable that the name of Dr. Black never

occurs in the whole paper, though we have seen that Lavoisier had

become acquainted with the doctrine of latent heat, at least as early

as the year 1772, as he mentioned the circumstance in a short paper

inserted that year in the Journal de Physique, and previously read to

the academy.

12. In the same volume of the Memoirs of the Academy, we have a paper

entitled "Experiments made by Order of the Academy, on the Cold

of the year 1775, by Messrs. Bezout, Lavoisier, and Vandermond."

It is sufficiently known that the beginning of the year 1776 was

distinguished in most parts of Europe by the weather. The object

of this paper, however, is rather to determine the accuracy of the

different thermometers at that time used in France, than to record the

lowest temperature which had been observed. It has some resemblance to

a paper drawn up about the same time by Mr. Cavendish, and published in

the Philosophical Transactions.

13. In the Memoirs of the Academy, for 1778, appeared a paper entitled

"Analysis of the Waters of the Lake Asphaltes, by Messrs. Macquer,

Lavoisier, and Sage." This water is known to be saturated with _salt_.

It is needless to state the result of the analysis contained in this

paper, because it is quite inaccurate. Chemical analysis had not at

that time made sufficient progress to enable chemists to analyze

mineral waters with precision.

The observation of Lavoisier and Guettard, which appeared at the

same time, on a species of steatite, which is converted by the fire

into a fine biscuit of porcelain, and on two coal-mines, the one in

Franche-Comté, the other in Alsace, do not require to be particularly

noticed.

14. In the Mem. de l'Académie, for 1780 (published in 1784), we have

a paper, by Lavoisier, "On certain Fluids which may be obtained in

an aeriform State, at a degree of Heat not much higher than the mean

Temperature of the Earth." These fluids are sulphuric ether, alcohol,

and water. He points out the boiling temperature of these liquids, and

shows that at that temperature the vapour of these bodies possesses

the elasticity of common air, and is permanent as long as the high

temperature continues. He burnt a mixture of vapour of ether and oxygen

gas, and showed that during the combustion carbonic acid gas is formed.

Lavoisier's notions respecting these vapours, and what hindered the

liquids at the boiling temperature from being all converted into vapour

were not quite correct. Our opinions respecting steam and vapours in

general were first rectified by Mr. Dalton.

15. In the Mem. de l'Académie, for 1780, appeared also the celebrated

paper on _heat_, by Lavoisier and Laplace. The object of this paper was

to determine the specific heat of various bodies, and to investigate

the proposals that had been made by Dr. Irvine for determining the

point at which a thermometer would stand, if plunged into a body

destitute of heat. This point is usually called the real zero.

They begin by describing an instrument which they had contrived to

measure the quantity of heat which leaves a body while it is cooling

a certain number of degrees. To this instrument they gave the name of

_calorimeter_. It consisted of a kind of hollow, surrounded on every

side by ice. The hot body was put into the centre. The heat which it

gave out while cooling was all expended in melting the ice, which was

of the temperature of 32°, and the quantity of heat was proportional

to the quantity of ice melted. Hence the quantity of ice melted, while

equal weights of hot bodies were cooling a certain number of degrees,

gave the direct ratios of the specific heats of each. In this way they

obtained the following specific heats:

Specific heat.

Water 1

Sheet-iron 0·109985

Glass without lead (crystal) 0·1929

Mercury 0·029

Quicklime 0·21689

Mixture of 9 water with 16 lime 0·439116

Sulphuric acid of 1·87058 0·334597

4 sulphuric acid, 3 water 0·603162

4 sulphuric acid, 5 water 0·663102

Nitric acid of 1·29895 0·661391

9⅓ nitric acid, 1 lime 0·61895

1 saltpetre, 8 water 0·8167

Their experiments were inconsistent with the conclusions drawn by Dr.

Irvine, respecting the real zero, from the diminution of the specific

heat, and the heat evolved when sulphuric acid was mixed with various

proportions of water, &c. If the experiments of Lavoisier and Laplace

approached nearly to accuracy, or, indeed, unless they were quite

inaccurate, it is obvious that the conclusions of Irvine must be quite

erroneous. It is remarkable that though the experiments of Crawford,

and likewise those of Wilcke, and of several others, on specific heat

had been published before this paper made its appearance, no allusion

whatever is made to these publications. Were we to trust to the

information communicated in the paper, the doctrine of specific heat

originated with Lavoisier and Laplace. It is true that in the fourth

part of the paper, which treats of combustion and respiration, Dr.

Crawford's, theory of animal heat is mentioned, showing clearly that

our authors were acquainted with his book on the subject. And, as this

theory is founded on the different specific heats of bodies, there

could be no doubt that he was acquainted with that doctrine.

16. In the Mem. de l'Académie, for 1780, occur the two following

memoirs:

Report made to the Royal Academy of Sciences on the Prisons. By Messrs.

Duhamel, De Montigny, Le Roy, Tenon, Tillet, and Lavoisier.

Report on the Process for separating Gold and Silver. By Messrs.

Macquer, Cadet, Lavoisier, Baumé, Cornette, and Berthollet.

17. In the Mem. de l'Académie, for 1781, we find a memoir by Lavoisier

and Laplace, on the electricity evolved when bodies are evaporated or

sublimed. The result of these experiments was, that when water was

evaporated electricity was always evolved. They concluded from these

observations, that whenever a body changes its state electricity

is always evolved. But when Saussure attempted to repeat these

observations, he could not succeed. And, from the recent experiments

of Pouillet, it seems to follow that electricity is evolved only when

bodies undergo chemical decomposition or combination. Such experiments

depend so much upon very minute circumstances, which are apt to escape

the attention of the observer, that implicit confidence cannot be

put in them till they have been often repeated, and varied in every

possible manner.

18. In the Memoires de l'Académie, for 1781, there is a paper by

Lavoisier on the comparative value of the different substances

employed as articles of fuel. The substances compared to each other

are pit-coal, coke, charcoal, and wood. It would serve no purpose to

state the comparison here, as it would not apply to this country; nor,

indeed, would it at present apply even to France.

We have, in the same volume, his paper on the mode of illuminating

theatres.

19. In the Memoires de l'Académie, for 1782 (printed in 1785), we

have a paper by Lavoisier on a method of augmenting considerably the

action of fire and of heat. The method which he proposes is a jet of

oxygen gas, striking against red-hot charcoal. He gives the result

of some trials made in this way. Platinum readily melted. Pieces of

ruby or sapphire were softened sufficiently to run together into one

stone. Hyacinth lost its colour, and was also softened. Topaz lost its

colour, and melted into an opaque enamel. Emeralds and garnets lost

their colour, and melted into opaque coloured glasses. Gold and silver

were volatilized; all the other metals, and even the metallic oxides,

were found to burn. Barytes also burns when exposed to this violent

heat. This led Lavoisier to conclude, as Bergman had done before him,

that Barytes is a metallic oxide. This opinion has been fully verified

by modern chemists. Both silica and alumina were melted. But he could

not fuse lime nor magnesia. We are now in possession of a still more

powerful source of heat in the oxygen and hydrogen blowpipe, which is

capable of fusing both lime and magnesia, and, indeed, every substance

which can be raised to the requisite heat without burning or being

volatilized. This subject was prosecuted still further by Lavoisier

in another paper inserted in a subsequent volume of the Memoires de

l'Académie. He describes the effect on rock-crystal, quartz, sandstone,

sand, phosphorescent quartz, milk quartz, agate, chalcedony, cornelian,

flint, prase, nephrite, jasper, felspar, &c.

20. In the same volume is inserted a memoir "On the Nature of the

aeriform elastic Fluids which are disengaged from certain animal

Substances in a state of Fermentation." He found that a quantity of

recent human fæces, amounting to about five cubic inches, when kept

at a temperature approaching to 60° emitted, every day for a month,

about half a cubic inch of gas. This gas was a mixture of eleven parts

carbonic acid gas, and one part of an inflammable gas, which burnt

with a blue flame, and was therefore probably carbonic oxide. Five

cubic inches of old human fæces from a necessary kept in the same

temperature, during the first fifteen days emitted about a third of

a cubic inch of gas each day; and during each of the second fifteen

days, about one fourth of a cubic inch. This gas was a mixture of

thirty-eight volumes of carbonic acid gas, and sixty-two volumes of a

combustible gas, burning with a blue flame, and probably carbonic oxide.

Fresh fæces do not effervesce with dilute sulphuric acid, but old moist

fæces do, and emit about eight times their volume of carbonic acid

gas. Quicklime, or caustic potash, mixed with fæces, puts a stop to

the evolution of gas, doubtless by preventing all fermentation. During

effervescence of fæcal matter the air surrounding it is deprived of a

little of its oxygen, probably in consequence of its combining with the

nascent inflammable gas which is slowly disengaged.

II. We come now to the new theory of combustion of which Lavoisier

was the author, and upon which his reputation with posterity will

ultimately depend. Upon this subject, or at least upon matters more

or less intimately connected with it, no fewer than twenty-seven

memoirs of his, many of them of a very elaborate nature, and detailing

expensive and difficult experiments, appeared in the different

volumes of the academy between 1774 and 1788. The analogy between the

combustion of bodies and the calcination of metals had been already

observed by chemists, and all admitted that both processes were

owing to the same cause; namely, the emission of _phlogiston_ by the

burning or calcining body. The opinion adopted by Lavoisier was, that

during burning and calcination nothing whatever left the bodies, but

that they simply united with a portion of the air of the atmosphere.

When he first conceived this opinion he was ignorant of the nature

of atmospheric air, and of the existence of oxygen gas. But after

that principle had been discovered, and shown to be a constituent of

atmospherical air, he soon recognised that it was the union of oxygen

with the burning and calcining body that occasioned the phenomena. Such

is the outline of the Lavoisierian theory stated in the simplest and

fewest words. It will be requisite to make a few observations on the

much-agitated question whether this theory originated with him.

It is now well known that John Rey, a physician at Bugue, in Perigord,

published a book in 1630, in order to explain the cause of the increase

of weight which lead and tin experience during their calcination. After

refuting in succession all the different explanations of this increase

of weight which had been advanced, he adds, "To this question, then,

supported on the grounds already mentioned, I answer, and maintain

with confidence, that the increase of weight arises from the air,

which is condensed, rendered heavy and adhesive by the violent and

long-continued heat of the furnace. This air mixes itself with the calx

(frequent agitation conducing), and attaches itself to the minutest

molecules, in the same manner as water renders heavy sand which is

agitated with it, and moistens and adheres to the smallest grains."

There cannot be the least doubt from this passage that Rey's opinion

was precisely the same as the original one of Lavoisier, and had

Lavoisier done nothing more than merely state in general terms that

during calcination air unites with the calcining bodies, it might have

been suspected that he had borrowed his notions from those of Rey. But

the discovery of oxygen, and the numerous and decisive proofs which

he brought forward that during burning and calcination oxygen unites

with the burning and calcining body, and that this oxygen may be again

separated and exhibited in its original elastic state oblige us to

alter our opinion. And whether we admit that he borrowed his original

notion from Rey, or that it suggested itself to his own mind, the case

will not be materially altered. For it is not the man who forms the

first vague notion of a thing that really adds to the stock of our

knowledge, but he who demonstrates its truth and accurately determines

its nature.

Rey's book and his opinions were little known. He had not brought

over a single convert to his doctrine, a sufficient proof that he had

not established it by satisfactory evidence. We may therefore believe

Lavoisier's statement, when he assures us that when he first formed his

theory he was ignorant of Rey, and never had heard that any such book

had been published.

The theory of combustion advanced by Dr. Hook, in 1665, in his

Micrographia, approaches still nearer to that of Lavoisier than

the theory of Rey, and indeed, so far as he has explained it, the

coincidence is exact. According to Hook there exists in common air a

certain substance which is like, if not the very same with that which

is fixed in saltpetre. This substance has the property of dissolving

all combustibles; but only when their temperature is sufficiently

raised. The solution takes place with such rapidity that it occasions

fire, which in his opinion is mere _motion_. The dissolved substance

may be in the state of air, or coagulated in a liquid or solid form.

The quantity of this solvent in a given bulk of air is incomparably

less than in the same bulk of saltpetre. Hence the reason why a

combustible continues burning but a short time in a given bulk of air:

the solvent is soon saturated, and then of course the combustion is

at an end. This explains why combustion requires a constant supply

of fresh air, and why it is promoted by forcing in air with bellows.

Hook promised to develop this theory at greater length in a subsequent

work; but he never fulfilled his promise; though in his Lampas,

published about twelve years afterwards, he gives a beautiful chemical

explanation of flame, founded on the very same theory.

From the very general terms in which Hook expresses himself, we cannot

judge correctly of the extent of his knowledge. This theory, so far as

it goes, coincides exactly with our present notions on the subject.

His solvent is oxygen gas, which constitutes one-fifth part of the

volume of the air, but exists in much greater quantity in saltpetre.

It combines with the burning body, and the compound formed may either

be a gas, a liquid, or a solid, according to the nature of the body

subjected to combustion.

Lavoisier nowhere alludes to this theory of Hook nor gives the least

hint that he had ever heard of it. This is the more surprising,

because Hook was a man of great celebrity; and his Micrographia, as

containing the original figures and descriptions of many natural

objects, is well known, not merely in Great Britain, but on the

continent. At the same time it must be recollected that Hook's theory

is supported by no evidence; that it is a mere assertion, and that

nobody adopted it. Even then, if we were to admit that Lavoisier was

acquainted with this theory, it would derogate very little from his

merit, which consisted in investigating the phenomena of combustion and

calcination, and in showing that oxygen became a constituent of the

burnt and calcined bodies.

About ten years after the publication of the Micrographia, Dr. Mayow,

of Oxford, published his Essays. In the first of which, De Sal-nitro

et Spiritu Nitro-aëreo, he obviously adopts Dr. Hook's theory of

combustion, and he applies it with great ingenuity to explain the

nature of respiration. Dr. Mayow's book had been forgotten when the

attention of men of science was attracted to it by Dr. Beddoes. Dr.

Yeats, of Bedford, published a very interesting work on the merits of

Mayow, in 1798. It will be admitted at once by every person who takes

the trouble of perusing Mayow's tract, that he was not satisfied with

mere theory; but proved by actual experiment that air was absorbed

during combustion, and altered during respiration. He has given

figures of his apparatus, and they are very much of the same nature

with those afterwards made use of by Lavoisier. It would be wrong,

therefore, to deprive Mayow of the reputation to which he is entitled

for his ingeniously-contrived and well-executed experiments. It must be

admitted that he proved both the absorption of air during combustion

and respiration; but even this does not take much from the fair

fame of Lavoisier. The analysis of air and the discovery of oxygen

gas really diminish the analogy between the theories of Mayow and

Lavoisier, or at any rate the full investigation of the subject and the

generalization of it belong exclusively to Lavoisier.

Attempts were made by the other French chemists, about the beginning

of the revolution, to associate themselves with Lavoisier, as equally

entitled with himself to the merit of the antiphlogistic theory; but

Lavoisier himself has disclaimed the partnership. Some years before his

death, he had formed the plan of collecting together all his papers

relating to the antiphlogistic theory and publishing them in one work;

but his death interrupted the project. However, his widow afterwards

published the first two volumes of the book, which were complete at the

time of his death. In one of these volumes Lavoisier claims for himself

the exclusive discovery of the cause of the augmentation of weight

which bodies undergo during combustion and calcination. He informs us

that a set of experiments, which he made in 1772, upon the different

kinds of air which are disengaged in effervescence, and a great number

of other chemical operations discovered to him demonstratively the

cause of the augmentation of weight which metals experience when

exposed to heat. "I was young," says he, "I had newly entered the lists

of science, I was desirous of fame, and I thought it necessary to

take some steps to secure to myself the property of my discovery. At

that time there existed an habitual correspondence between the men of

science of France and those of England. There was a kind of rivality

between the two nations, which gave importance to new experiments,

and which sometimes was the cause that the writers of the one or the

other of the nations disputed the discovery with the real author.

Consequently, I thought it proper to deposit on the 1st of November,

1772, the following note in the hands of the secretary of the academy.

This note was opened on the 1st of May following, and mention of these

circumstances marked at the top of the note. It was in the following

terms:

"About eight days ago I discovered that sulphur in burning, far from

losing, augments in weight; that is to say, that from one pound of

sulphur much more than one pound of vitriolic acid is obtained, without

reckoning the humidity of the air. Phosphorus presents the same

phenomenon. This augmentation of weight arises from a great quantity of

air, which becomes fixed during the combustion, and which combines with

the vapours.

"This discovery, which I confirmed by experiments which I regard as

decisive, led me to think that what is observed in the combustion of

sulphur and phosphorus, might likewise take place with respect to all

the bodies which augment in weight by combustion and calcination;

and I was persuaded that the augmentation of weight in the calces of

metals proceeded from the same cause. The experiment fully confirmed my

conjectures. I operated the reduction of litharge in close vessels with

Hales's apparatus, and I observed, that at the moment of the passage

of the calx into the metallic state, there was a disengagement of air

in considerable quantity, and that this air formed a volume at least

one thousand times greater than that of the litharge employed. As this

discovery appears to me one of the most interesting which has been made

since Stahl, I thought it expedient to secure to myself the property,

by depositing the present note in the hands of the secretary of the

academy, to remain secret till the period when I shall publish my

experiments.

"LAVOISIER.

"_Paris, November 11, 1772._"

This note leaves no doubt that Lavoisier had conceived his theory, and

confirmed it by experiment, at least as early as November, 1772. But at

that time the nature of air and the existence of oxygen were unknown.

The theory, therefore, as he understood it at that time, was precisely

the same as that of John Rey. It was not till the end of 1774 that his

views became more precise, and that he was aware that oxygen is the

portion of the air which unites with bodies during combustion, and

calcination.

Nothing can be more evident from the whole history of the academy,

and of the French chemists during this eventful period, for the

progress of the science, that none of them participated in the views

of Lavoisier, or had the least intention of giving up the phlogistic

theory. It was not till 1785, after his experiments had been almost all

published, and after all the difficulties had been removed by the two

great discoveries of Mr. Cavendish, that Berthollet declared himself a

convert to the Lavoisierian opinions. This was soon followed by others,

and within a very few years almost all the chemists and men of science

in France enlisted themselves on the same side. Lavoisier's objection,

then, to the phrase _La Chimie Française_, is not without reason, the

term _Lavoisierian Chemistry_ should undoubtedly be substituted for

it. This term, _La Chimie Française_ was introduced by Fourcroy. Was

Fourcroy anxious to clothe himself with the reputation of Lavoisier,

and had this any connexion with the violent death of that illustrious

man?

The first set of experiments which Lavoisier published on his peculiar

views, was entitled, "A Memoir on the Calcination of Tin in close

Vessels; and on the Cause of the increase of Weight which the Metal

acquires during this Process." It appeared in the Memoirs of the

Academy, for 1774. In this paper he gives an account of several

experiments which he had made on the calcination of tin in glass

retorts, hermetically sealed. He put a quantity of tin (about half a

pound) into a glass retort, sometimes of a larger and sometimes of a

smaller size, and then drew out the beak into a capillary tube. The

retort was now placed upon the sand-bath, and heated till the tin just

melted. The extremity of the capillary beak of the retort was now

fused so as to seal it hermetically. The object of this heating was to

prevent the retort from bursting by the expansion of the air during the

process. The retort, with its contents, was now carefully weighed, and

the weight noted. It was put again on the sand-bath, and kept melted

till the process of calcination refused to advance any further. He

observed, that if the retort was small, the calcination always stopped

sooner than it did if the retort was large. Or, in other words, the

quantity of tin calcined was always proportional to the size of the

retort.

After the process was finished, the retort (still hermetically sealed)

was again weighed, and was always found to have the same weight exactly

as at first. The beak of the retort was now broken off, and a quantity

of air entered with a hissing noise. The increase of weight was now

noted: it was obviously owing to the air that had rushed in. The weight

of air that had been at first driven out by the fusion of the tin had

been noted, and it was now found that a considerably greater quantity

had entered than had been driven out at first. In some experiments,

as much as 10·06 grains, in others 9·87 grains, and in some less than

this, when the size of the retort was small. The tin in the retort was

mostly unaltered, but a portion of it had been converted into a black

powder, weighing in some cases above two ounces. Now it was found in

all cases, that the weight of the tin had increased, and the increase

of weight was always exactly equal to the diminution of weight which

the air in the retort had undergone, measured by the quantity of new

air which rushed in when the beak of the retort was broken, minus the

air that had been driven out when the tin was originally melted before

the retort was hermetically sealed.

Thus Lavoisier proved by these first experiments, that when tin

is calcined in close vessels a portion of the air of the vessel

disappears, and that the tin increases in weight just as much as is

equivalent to the loss of weight which the air has sustained. He

therefore inferred, that this portion of air had united with the tin,

and that calx of tin is a compound of tin and air. In this first paper

there is nothing said about oxygen, nor any allusion to lead to the

suspicion that air is a compound of different elastic fluids. These,

therefore, were probably the experiments to which Lavoisier alludes in

the note which he lodged with the secretary of the academy in November,

1772.

He mentions towards the end of the Memoir that he had made similar

experiments with lead; but he does not communicate any of the numerical

results: probably because the results were not so striking as those

with tin. The heat necessary to melt lead is so high that satisfactory

experiments on its calcination could not easily be made in a glass

retort.

Lavoisier's next Memoir appeared in the Memoirs of the Academy, for

1775, which were published in 1778. It is entitled, "On the Nature of

the Principle which combines with the Metals during their Calcination,

and which augments their Weight." He observes that when the metallic

calces are reduced to the metallic state it is found necessary to

heat them along with charcoal. In such cases a quantity of carbonic

acid gas is driven off, which he assures us is the charcoal united to

the elastic fluid contained in the calx. He tried to reduce the calx

of iron by means of burning-glasses, while placed under large glass

receivers standing over mercury; but as the gas thus evolved was mixed

with a great deal of common air which was necessarily left in the

receiver, he was unable to determine its nature. This induced him to

have recourse to red oxide of mercury. He showed in the first place

that this substance (_mercurius præcipitatus per se_) was a true calx,

by mixing it with charcoal powder in a retort and heating it. The

mercury was reduced and abundance of carbonic acid gas was collected

in an inverted glass jar standing in a water-cistern into which the

beak of the retort was plunged. On heating the red oxide of mercury

by itself it was reduced to the metallic state, though not so easily,

and at the same time a gas was evolved which possessed the following

properties:

1. It did not combine with water by agitation.

2. It did not precipitate lime-water.

3. It did not unite with fixed or volatile alkalies.

4. It did not at all diminish their caustic quality.

5. It would serve again for the calcination of metals.

6. It was diminished like common air by addition of one-third of

nitrous gas.

7. It had none of the properties of carbonic acid gas. Far from being

fatal, like that gas, to animals, it seemed on the contrary more proper

for the purposes of respiration. Candles and burning bodies were not

only not extinguished by it, but burned with an enlarged flame in

a very remarkable manner. The light they gave was much greater and

clearer than in common air.

He expresses his opinion that the same kind of air would be obtained by

heating nitre without addition, and this opinion is founded on the fact

that when nitre is detonated with charcoal it gives out abundance of

carbonic acid gas.

Thus Lavoisier shows in this paper that the kind of air which unites

with metals during their calcination is purer and fitter for combustion

than common air. In short it is the gas which Dr. Priestley had

discovered in 1774, and which is now known by the name of oxygen gas.

This Memoir deserves a few animadversions. Dr. Priestley discovered

oxygen gas in August, 1774; and he informs us in his life, that in

the autumn of that year he went to Paris and exhibited to Lavoisier,

in his own laboratory the mode of obtaining oxygen gas by heating

red oxide of mercury in a gun-barrel, and the properties by which

this gas is distinguished--indeed the very properties which Lavoisier

himself enumerates in his paper. There can, therefore, be no doubt that

Lavoisier was acquainted with oxygen gas in 1774, and that he owed his

knowledge of it to Dr. Priestley.

There is some uncertainty about the date of Lavoisier's paper. In the

History of the Academy, for 1775, it is merely said about it, "Read at

the resumption (_rentrée_) of the Academy, on the 26th of April, by M.

Lavoisier," without naming the year. But it could not have been before

1775, because that is the year upon the volume of the Memoirs; and

besides, we know from the Journal de Physique (v. 429), that 1775 was

the year on which the paper of Lavoisier was read.

Yet in the whole of this paper the name of Dr. Priestley never occurs,

nor is the least hint given that he had already obtained oxygen gas by

heating red oxide of mercury. So far from it, that it is obviously the

intention of the author of the paper to induce his readers to infer

that he himself was the discoverer of oxygen gas. For after describing

the process by which oxygen gas was obtained by him, he says nothing

further remained but to determine its nature, and "I discovered with

_much surprise_ that it was not capable of combination with water

by agitation," &c. Now why the expression of surprise in describing

phenomena which had been already shown? And why the omission of all

mention of Dr. Priestley's name? I confess that this seems to me

capable of no other explanation than a wish to claim for himself the

discovery of oxygen gas, though he knew well that that discovery had

been previously made by another.

The next set of experiments made by Lavoisier to confirm or extend

his theory, was "On the Combustion of Phosphorus, and the Nature of

the Acid which results from that Combustion." It appeared in the

Memoirs of the Academy, for 1777. The result of these experiments

was very striking. When phosphorus is burnt in a given bulk of air

in sufficient quantity, about four-fifths of the volume of the air

disappears and unites itself with the phosphorus. The residual portion

of the air is incapable of supporting combustion or maintaining animal

life. Lavoisier gave it the name of _mouffette atmospherique_, and he

describes several of its properties. The phosphorus by combining with

the portion of air which has disappeared, is converted into phosphoric

acid, which is deposited on the inside of the receiver in which the

combustion is performed, in the state of fine white flakes. One grain

by this process is converted into two and a half grains of phosphoric

acid. These observations led to the conclusion that atmospheric air

is a mixture or compound of two distinct gases, the one (_oxygen_)

absorbed by burning phosphorus, the other (_azote_) not acted on by

that principle, and not capable of uniting with or calcining metals.

These conclusions had already been drawn by Scheele from similar

experiments, but Lavoisier was ignorant of them.

In the second part of this paper, Lavoisier describes the properties

of phosphoric acid, and gives an account of the salts which it forms

with the different bases. The account of these salts is exceedingly

imperfect, and it is remarkable that Lavoisier makes no distinction

between phosphate of potash and phosphate of soda; though the different

properties of these two salts are not a little striking. But these were

not the investigations in which Lavoisier excelled.

The next paper in which the doctrines of the antiphlogistic theory

were still further developed, was inserted in the Memoirs of the

Academy, for 1777. It is entitled, "On the Combustion of Candles in

atmospherical Air, and in Air eminently Respirable." This paper is

remarkable, because in it he first notices Dr. Priestley's discovery of

oxygen gas; but without any reference to the preceding paper, or any

apology for not having alluded in it to the information which he had

received from Dr. Priestley.

He begins by saying that it is necessary to distinguish four different

kinds of air. 1. Atmospherical air in which we live, and which we

breath. 2. Pure air (_oxygen_), alone fit for breathing, constituting

about the fourth of the volume of atmospherical air, and called by Dr.

Priestley _dephlogisticated air_. 3. Azotic gas, which constitutes

about three-fourths of the volume of atmospherical air, and whose

properties are still unknown. 4. Fixed air, which he proposed to call

(as Bucquet had done) _acide crayeux_, _acid of chalk_.

In this paper Lavoisier gives an account of a great many trials that

he made by burning candles in given volumes of atmospherical air and

oxygen gas enclosed in glass receivers, standing over mercury. The

general conclusion which he deduces from these experiments are--that

the azotic gas of the air contributes nothing to the burning of

the candle; but the whole depends upon the oxygen gas of the air,

constituting in his opinion one-fourth of its volume; that during the

combustion of a candle in a given volume of air only two-fifths of

the oxygen are converted into carbonic acid gas, while the remaining

three-fifths remain unaltered; but when the combustion goes on in

oxygen gas a much greater proportion (almost the whole) of this gas

is converted into carbonic acid gas. Finally, that phosphorus, when

burnt in air acts much more powerfully on the oxygen of the air than a

lighted candle, absorbing four-fifths of the oxygen and converting it

into phosphoric acid.

It is evident that at the time this paper was written, Lavoisier's

theory was nearly complete. He considered air as a mixture of three

volumes of azotic gas, and one volume of oxygen gas. The last alone

was concerned in combustion and calcination. During these processes a

portion of the oxygen united with the burning body, and the compound

formed constituted the acid or the calx. Thus he was able to account

for combustion and calcination without having recourse to phlogiston.

It is true that several difficulties still lay in his way, which he

was not yet able to obviate, and which prevented any other person from

adopting his opinions. One of the greatest of these was the fact that

hydrogen gas was evolved during the solution of several metals in

dilute sulphuric or muriatic acid; that by this solution these metals

were converted into calces, and that calces, when heated in hydrogen

gas, were reduced to the metallic state while the hydrogen disappeared.

The simplest explanation of these phenomena was the one adopted by

chemists at the time. Hydrogen was considered as phlogiston. By

dissolving metals in acids, the phlogiston was driven off and the calx

remained: by heating the calx in hydrogen, the phlogiston was again

absorbed and the calx reduced to the metallic state.

This explanation was so simple and appeared so satisfactory, that it

was universally adopted by chemists with the exception of Lavoisier

himself. There was a circumstance, however, which satisfied him that

this explanation, however plausible, was not correct. The calx was

_heavier_ than the metal from which it had been produced. And hydrogen,

though a light body, was still possessed of weight. It was obviously

impossible, then, that the metal could be a combination of the calx and

hydrogen. Besides, he had ascertained by direct experiment, that the

calces of mercury, tin, and lead are compounds of the respective metals

and oxygen. And it was known that when the other calces were heated

with charcoal, they were reduced to the metallic state, and at the same

time carbonic acid gas is evolved. The very same evolution takes place

when calces of mercury, tin, and lead, are heated with charcoal powder.

Hence the inference was obvious that carbonic acid is a compound of

charcoal and oxygen, and therefore that all calces are compounds of

their respective metals and oxygen.

Thus, although Lavoisier was unable to account for the phenomena

connected with the evolution and absorption of hydrogen gas, he had

conclusive evidence that the orthodox explanation was not the true one.

He wisely, therefore, left it to time to throw light upon those parts

of the theory that were still obscure.

His next paper, which was likewise inserted in the Memoirs of the

Academy, for 1777, had some tendency to throw light on this subject,

or at least it elucidated the constitution of sulphuric acid, which

bore directly upon the antiphlogistic theory. It was entitled, "On the

Solution of Mercury in vitriolic Acid, and on the Resolution of that

Acid into aeriform sulphurous Acid, and into Air eminently Respirable."

He had already proved that sulphuric acid is a compound of sulphur and

oxygen; and had even shown how the oxygen which the acid contained

might be again separated from it, and exhibited in a separate state.

Dr. Priestley had by this time made known the method of procuring

sulphurous acid gas, by heating a mixture of mercury and sulphuric

acid in a phial. This was the process which Lavoisier analyzed in the

present paper. He put into a retort a mixture of four ounces mercury

and six ounces concentrated sulphuric acid. The beak of the retort was

plunged into a mercurial cistern, to collect the sulphurous acid gas

as it was evolved; and heat being applied to the belly of the retort,

sulphurous acid gas passed over in abundance, and sulphate of mercury

was formed. The process was continued till the whole liquid contents

of the retort had disappeared: then a strong heat was applied to the

salt. In the first place, a quantity of sulphurous acid gas passed

over, and lastly a portion of oxygen gas. The quicksilver was reduced

to the metallic state. Thus he resolved sulphuric acid into sulphurous

acid and oxygen. Hence it followed as a consequence, that sulphurous

acid differs from sulphuric merely by containing a smaller quantity of

oxygen.

The object of his next paper, published at the same time, was to throw

light upon the pyrophorus of Homberg, which was made by kneading

alum into a cake, with flour, or some substance containing abundance

of carbon, and then exposing the mixture to a strong heat in close

vessels, till it ceased to give out smoke. It was known that a

pyrophorus thus formed takes fire of its own accord, and burns when it

comes in contact with common air. It will not be necessary to enter

into a minute analysis of this paper, because, though the experiments

were very carefully made, yet it was impossible, at the time when the

paper was drawn, to elucidate the phenomena of this pyrophorus in a

satisfactory manner. There can be little doubt that the pyrophorus owes

its property of catching fire, when in contact with air or oxygen,

to a little potassium, which has been reduced to the metallic state

by the action of the charcoal and sulphur on the potash in the alum.

This substance taking fire, heat enough is produced to set fire to the

carbon and sulphur which the pyrophorus contains. Lavoisier ascertained

that during its combustion a good deal of carbonic acid was generated.

There appeared likewise another paper by Lavoisier, in the same volume

of the academy, which may be mentioned, as it served still further to

demonstrate the truth of the antiphlogistic theory. It is entitled, "On

the Vitriolization of Martial Pyrites." Iron pyrites is known to be a

compound of _iron_ and _sulphur_. Sometimes this mineral may be left

exposed to the air without undergoing any alteration, while at other

times it speedily splits, effloresces, swells, and is converted into

sulphate of iron. There are two species of pyrites; the one composed

of two atoms of sulphur and one atom of iron, the other of one atom of

sulphur and one atom of iron. The first of these is called bisulphuret

of iron; the second protosulphuret, or simply sulphuret of iron. The

variety of pyrites which undergoes spontaneous decomposition in the

air, is known to be a compound, or rather mixture of the two species of

pyrites.

Lavoisier put a quantity of the decomposing pyrites under a glass jar,

and found that the process went on just as well as in the open air.

He found that the air was deprived of the whole of its oxygen by the

process, and that nothing was left but azotic gas. Hence the nature

of the change became evident. The sulphur, by uniting with oxygen,

was converted into sulphuric acid, while the iron became oxide of

iron, and both uniting, formed sulphate of iron. There are still some

difficulties connected with this change that require to be elucidated.

We have still another paper by Lavoisier, bearing on the antiphlogistic

theory, published in the same volume of the Memoirs of the Academy,

for 1778, entitled, "On Combustion in general." He establishes that

the only air capable of supporting combustion is oxygen gas: that

during the burning of bodies in common air, a portion of the oxygen of

the atmosphere disappears, and unites with the burning body, and that

the new compound formed is either an acid or a metallic calx. When

sulphur is burnt, sulphuric acid is formed; when phosphorus, phosphoric

acid; and when charcoal, carbonic acid. The calcination of metals is

a process analogous to combustion, differing chiefly by the slowness

of the process: indeed when it takes place rapidly, actual combustion

is produced. After establishing these general principles, which are

deduced from his preceding papers, he proceeds to examine the Stahlian

theory of phlogiston, and shows that no evidence of the existence of

any such principle can be adduced, and that the phenomena can all be

explained without having recourse to it. Powerful as these arguments

were, they produced no immediate effects. Nobody chose to give up the

phlogistic theory to which he had been so long accustomed.

The next two papers of Lavoisier require merely to be mentioned, as

they do not bear immediately upon the antiphlogistic theory. They

appeared in the Memoirs of the Academy, for 1780. These memoirs were,

1. Second Memoir on the different Combinations of Phosphoric Acid.

2. On a particular Process, by means of which Phosphorus may be

converted into phosphoric Acid, without Combustion.

The process here described consisted in throwing phosphorus, by a

few grains at a time, into warm nitric acid of the specific gravity

1·29895. It falls to the bottom like melted wax, and dissolves pretty

rapidly with effervescence: then another portion is thrown in, and the

process is continued till as much phosphorus has been employed as is

wanted; then the phosphoric acid may be obtained pure by distilling off

the remaining nitric acid with which it is still mixed.

Hitherto Lavoisier had been unable to explain the anomalies respecting

hydrogen gas, or to answer the objections urged against his theory

in consequence of these anomalies. He had made several attempts to

discover what peculiar substance was formed during the combustion of

hydrogen, but always without success: at last, in 1783, he resolved to

make the experiment upon so large a scale, that whatever the product

might be, it should not escape him; but Sir Charles Blagden, who

had just gone to Paris, informed him that the experiment for which

he was preparing had already been made by Mr. Cavendish, who had

ascertained that the product of the combustion of hydrogen was _water_.

Lavoisier saw at a glance the vast importance of this discovery for

the establishment of the antiphlogistic theory, and with what ease it

would enable him to answer all the plausible objections which had been

brought forward against his opinions in consequence of the evolution

of hydrogen, when metals were calcined by solution in acids, and the

absorption of it when metals were reduced in an atmosphere of this

gas. He therefore resolved to repeat the experiment of Cavendish with

every possible care, and upon a scale sufficiently large to prevent

ambiguity. The experiment was made on the 24th of June, 1783, by

Lavoisier and Laplace, in the presence of M. Le Roi, M. Vandermonde,

and Sir Charles Blagden, who was at that time secretary of the Royal

Society. The quantity of water formed was considerable, and they found

that water was a compound of

1 volume oxygen

1·91 volume hydrogen.

Not satisfied with this, he soon after made another experiment along

with M. Meusnier to decompose water. For this purpose a porcelain tube,

filled with iron wire, was heated red-hot by being passed through a

furnace, and then the steam of water was made to traverse the red-hot

wire. To the further extremity of the porcelain tube a glass tube was

luted, which terminated in a water-trough under an inverted glass

receiver placed to collect the gas. The steam was decomposed by the

red-hot iron wire, its oxygen united to the wire, while the hydrogen

passed on and was collected in the water-cistern.

Both of these experiments, though not made till 1783, and though the

latter of them was not read to the academy till 1784, were published in

the volume of the Memoirs for 1781.

It is easy to see how this important discovery enabled Lavoisier to

obviate all the objections to his theory from hydrogen. He showed that

it was evolved when zinc or iron was dissolved in dilute sulphuric

acid, because the water underwent decomposition, its oxygen uniting to

the zinc or iron, and converting it into an oxide, while its hydrogen

made its escape in the state of gas. Oxide of iron was reduced when

heated in contact with hydrogen gas, because the hydrogen united to

the oxygen of the acid and formed water, and of course the iron was

reduced to the state of a metal. I consider it unnecessary to enter

into a minute detail of these experiments, because, in fact, they

added very little to what had been already established by Cavendish.

But it was this discovery that contributed more than any thing else

to establish the antiphlogistic theory. Accordingly, the great object

of Dr. Priestley, and other advocates of the phlogistic theory, was

to disprove the fact that water is a compound of oxygen and hydrogen.

Scheele admitted the fact that water is a compound of oxygen and

hydrogen; and doubtless, had he lived, would have become a convert

to the antiphlogistic theory, as Dr. Black actually did. In short,

it was the discovery of the compound nature of water that gave the

Lavoisierian theory the superiority over that of Stahl. Till the time

of this discovery every body opposed the doctrine of Lavoisier; but

within a very few years after it, hardly any supporters of phlogiston

remained. Nothing could be more fortunate for Lavoisier than this

discovery, or afford him greater reason for self-congratulation.

We see the effect of this discovery upon his next paper, "On the

Formation of Carbonic Acid," which appeared in the Memoirs of the

Academy, for 1781. There, for the first time, he introduces new terms,

showing, by that, that he considered his opinions as fully established.

To the _dephlogisticated air_ of Priestley, or his own _pure air_, he

now gives the name of _oxygen_. The fixed air of Black he designates

_carbonic acid_, because he considered it as a compound of _carbon_

(the pure part of charcoal) and oxygen. The object of this paper is to

determine the proportion of the constituents. He details a great many

experiments, and deduces from them all, that carbonic acid gas is a

compound of

Carbon 0·75

Oxygen 1·93

Now this is a tolerably near approximation to the truth. The true

constituents, as determined by modern chemists, being

Carbon 0·75

Oxygen 2·00

The next paper of M. Lavoisier, which appeared in the Memoirs of the

Academy, for 1782 (published in 1785), shows how well he appreciated

the importance of the discovery of the composition of water. It is

entitled, "General Considerations on the Solution of the Metals in

Acids." He shows that when metals are dissolved in acids, they are

converted into oxides, and that the acid does not combine with the

metal, but only with its oxide. When nitric acid is the solvent the

oxidizement takes place at the expense of the acid, which is resolved

into nitrous gas and oxygen. The nitrous gas makes its escape, and may

be collected; but the oxygen unites with the metal and renders it an

oxide. He shows this with respect to the solution of mercury in nitric

acid. He collected the nitrous gas given out during the solution of

the metal in the acid: then evaporated the solution to dryness, and

urged the fire till the mercury was converted into red oxide. The fire

being still further urged, the red oxide was reduced, and the oxygen

gas given off was collected and measured. He showed that the nitrous

gas and the oxygen gas thus obtained, added together, formed just the

quantity of nitric acid which had disappeared during the process. A

similar experiment was made by dissolving iron in nitric acid, and then

urging the fire till the iron was freed from every foreign body, and

obtained in the state of black oxide.

It is well known that many metals held in solution by acids may be

precipitated in the metallic state, by inserting into the solution

a plate of some other metal. A portion of that new metal dissolves,

and takes the place of the metal originally in solution. Suppose, for

example, that we have a neutral solution of copper in sulphuric acid,

if we put into the solution a plate of iron, the copper is thrown down

in the metallic state, while a certain portion of the iron enters into

the solution, combining with the acid instead of the copper. But the

copper, while in solution, was in the state of an oxide, and it is

precipitated in the metallic state. The iron was in the metallic state;

but it enters into the solution in the state of an oxide. It is clear

from this that the oxygen, during these precipitations, shifts its

place, leaving the copper, and entering into combination with the iron.

If, therefore, in such a case we determine the exact quantity of copper

thrown down, and the exact quantity of iron dissolved at the same time,

it is clear that we shall have the relative weight of each combined

with the same weight of oxygen. If, for example, 4 of copper be thrown

down by the solution of 3·5 of iron; then it is clear that 3·5 of iron

requires just as much oxygen as 4 of copper, to turn both into the

oxide that exists in the solution, which is the black oxide of each.

Bergman had made a set of experiments to determine the proportional

quantities of phlogiston contained in the different metals, by the

relative quantity of each necessary to precipitate a given weight

of another from its acid solution. It was the opinion at that time,

that metals were compounds of their respective calces and phlogiston.

When a metal dissolved in an acid, it was known to be in the state

of calx, and therefore had parted with its phlogiston: when another

metal was put into this solution it became a calx, and the dissolved

metal was precipitated in the metallic state. It had therefore united

with the phlogiston of the precipitating metal. It is obvious, that

by determining the quantities of the two metals precipitated and

dissolved, the relative proportion of phlogiston in each could be

determined. Lavoisier saw that these experiments of Bergman would serve

equally to determine the relative quantity of oxygen in the different

oxides. Accordingly, in a paper inserted in the Memoirs of the Academy,

for 1782, he enters into an elaborate examination of Bergman's

experiments, with a view to determine this point. But it is unnecessary

to state the deductions which he drew, because Bergman's experiments

were not sufficiently accurate for the object in view. Indeed, as

the mutual precipitation of the metals is a galvanic phenomenon, and

as the precipitated metal is seldom quite pure, but an alloy of the

precipitating and precipitated metal; and as it is very difficult

to dry the more oxidizable metals, as copper and tin, without their

absorbing oxygen when they are in a state of very minute division;

this mode of experimenting is not precise enough for the object which

Lavoisier had in view. Accordingly the table of the composition of the

metallic oxides which Lavoisier has drawn up is so very defective, that

it is not worth while to transcribe it.

The same remark applies to the table of the affinities of oxygen which

Lavoisier drew up and inserted in the Memoirs of the Academy, for the

same year. His data were too imperfect, and his knowledge too limited,

to put it in his power to draw up any such table with any approach to

accuracy. I shall have occasion to resume the subject in a subsequent

chapter.

In the same volume of the Memoirs of the Academy, this indefatigable

man inserted a paper in order to determine the quantity of oxygen

which combines with iron. His method of proceeding was, to burn a

given weight of iron in oxygen gas. It is well known that iron wire,

under such circumstances, burns with considerable splendour, and that

the oxide, by the heat, is fused into a black brittle matter, having

somewhat of the metallic lustre. He burnt 145·6 grains of iron in this

way, and found that, after combustion, the weight became 192 grains,

and 97 French cubic inches of oxygen gas had been absorbed. From this

experiment it follows, that the oxide of iron formed by burning iron in

oxygen gas is a compound of

Iron 3·5

Oxygen 1·11

This forms a tolerable approximation to the truth. It is now

known, that the quantity of oxygen in the oxide of iron formed by

the combustion of iron in oxygen gas is not quite uniform in its

composition; sometimes it is a compound of

Iron 3½

Oxygen 1⅓

While at other times it consists very nearly of

Iron 3·5

Oxygen 1

and probably it may exist in all the intermediate proportions between

these two extremes. The last of these compounds constitutes what is

now known by the name of _protoxide_, or _black oxide of iron_. The

first is the composition of the ore of iron so abundant, which is

distinguished by the name of _magnetic iron ore_.

Lavoisier was aware that iron combines with more oxygen than exists

in the protoxide; indeed, his analysis of peroxide of iron forms a

tolerable approximation to the truth; but there is no reason for

believing that he was aware that iron is capable of forming only two

oxides, and that all intermediate degrees of oxidation are impossible.

This was first demonstrated by Proust.

I think it unnecessary to enter into any details respecting two papers

of Lavoisier, that made their appearance in the Memoirs of the Academy,

for 1783, as they add very little to what he had already done. The

first of these describes the experiments which he made to determine the

quantity of oxygen which unites with sulphur and phosphorus when they

are burnt: it contains no fact which he had not stated in his former

papers, unless we are to consider his remark, that the heat given out

during the burning of these bodies has no sensible weight, as new.

The other paper is "On Phlogiston;" it is very elaborate, but contains

nothing which had not been already advanced in his preceding memoirs.

Chemists were so wedded to the phlogistic theory, their prejudices

were so strong, and their understandings so fortified against every

thing that was likely to change their opinions, that Lavoisier found

it necessary to lay the same facts before them again and again, and to

place them in every point of view. In this paper he gives a statement

of his own theory of combustion, which he had previously done in

several preceding papers. He examines the phlogistic theory of Stahl at

great length, and refutes it.

In the Memoirs of the Academy, for 1784, Lavoisier published a very

elaborate set of experiments on the combustion of alcohol, oil, and

different combustible bodies, which gave a beginning to the analysis

of vegetable substances, and served as a foundation upon which this

most difficult part of chemistry might be reared. He showed that during

the combustion of alcohol the oxygen of the air united to the vapour

of the alcohol, which underwent decomposition, and was converted

into water and carbonic acid. From these experiments he deduced as a

consequence, that the constituents of alcohol are carbon, hydrogen,

and oxygen, and nothing else; and he endeavoured from his experiments

to determine the relative proportions of these different constituents.

From these experiments he concluded, that the alcohol which he used in

his experiments was a compound of

Carbon 2629·5 part.

Hydrogen 725·5

Water 5861

It would serve no purpose to attempt to draw any consequences from

these experiments; as Lavoisier does not mention the specific gravity

of the alcohol, of course we cannot say how much of the water found

was merely united with the alcohol, and how much entered into

its composition. The proportion between the carbon and hydrogen,

constitutes an approximation to the truth, though not a very near one.

Olive oil he showed to be a compound of hydrogen and carbon, and bees'

wax to be a compound of the same constituents, though in a different

proportion.

This subject was continued, and his views further extended, in a

paper inserted in the Memoirs of the Academy, for 1786, entitled,

"Reflections on the Decomposition of Water by Vegetable and Animal

Substances." He begins by stating that when charcoal is exposed to

a strong heat, it gives out a little carbonic acid gas and a little

inflammable air, and after this nothing more can be driven off, however

high the temperature be to which it is exposed; but if the charcoal

be left for some time in contact with the atmosphere it will again

give out a little carbonic acid gas and inflammable gas when heated,

and this process may be repeated till the whole charcoal disappears.

This is owing to the presence of a little moisture which the charcoal

imbibes from the air. The water is decomposed when the charcoal is

heated and converted into carbonic acid and inflammable gas. When

vegetable substances are heated in a retort, the water which they

contain undergoes a similar decomposition, the carbon which forms one

of their constituents combines with the oxygen and produces carbonic

acid, while the hydrogen, the other constituent of the water, flies

off in the state of gas combined with a certain quantity of carbon.

Hence the substances obtained when vegetable or animal substances

are distilled did not exist ready formed in the body operated on;

but proceeded from the double decompositions which took place by the

mutual action of the constituents of the water, sugar, mucus, &c.,

which the vegetable body contains. The oil, the acid, &c., extracted

by distilling vegetable bodies did not exist in them, but are formed

during the mutual action of the constituents upon each other,

promoted as their action is by the heat. These views were quite new

and perfectly just, and threw a new light on the nature of vegetable

substances and on the products obtained by distilling them. It showed

the futility of all the pretended analyses of vegetable substances,

which chemists had performed by simply subjecting them to distillation,

and the error of drawing any conclusions respecting the constituents

of vegetable substances from the results of their distillation, except

indeed with respect to their elementary constituents. Thus when by

distilling a vegetable substance we obtain water, oil, acetic acid,

carbonic acid, and carburetted hydrogen, we must not conclude that

these principles existed in the substance, but merely that it contained

carbon, hydrogen, and oxygen, in such proportions as to yield all these

principles by decompositions.

As nitric acid acts upon metals in a very different way from sulphuric

and muriatic acids, and as it is a much better solvent of metals in

general than any other, it was an object of great importance towards

completing the antiphlogistic theory to obtain an accurate knowledge

of its constituents. Though Lavoisier did not succeed in this, yet he

made at least a certain progress, which enabled him to explain the

phenomena, at that time known, with considerable clearness, and to

answer all the objections to the antiphlogistic theory from the action

of nitric acid on metals. His first paper on the subject was published

in the Memoirs of the Academy, for 1776. He put a quantity of nitric

acid and mercury into a retort with a long beak, which he plunged into

the water-trough. An effervescence took place and gas passed over

in abundance, and was collected in a glass jar; the mercury being

dissolved the retort was still further heated, till every thing liquid

passed over into the receiver, and a dry yellow salt remained. The beak

of the retort was now again plunged into the water-trough, and the salt

heated till all the nitric acid which it contained was decomposed,

and nothing remained in the retort but red oxide of mercury. During

this last process much more gas was collected. All the gas obtained

during the solution of the mercury and the decomposition of the salt

was nitrous gas. The red oxide of mercury was now heated to redness,

oxygen gas was emitted in abundance, and the mercury was reduced to the

metallic state: its weight was found the very same as at first. It is

clear, therefore, that the nitrous gas and the oxygen gas were derived,

not from the mercury but from the nitric acid, and that the nitric acid

had been decomposed into nitrous gas and oxygen: the nitrous gas had

made its escape in the form of gas, and the oxygen had remained united

to the metal.

From these experiments it follows clearly, that nitric acid is a

compound of nitrous gas and oxygen. The nature of nitrous gas itself

Lavoisier did not succeed in ascertaining. It passed with him for a

simple substance; but what he did ascertain enabled him to explain

the action of nitric acid on metals. When nitric acid is poured upon

a metal which it is capable of dissolving, copper for example, or

mercury, the oxygen of the acid unites to the metal, and converts into

an oxide, while the nitrous gas, the other constituent of the acid,

makes its escape in the gaseous form. The oxide combines with and is

dissolved by another portion of the acid which escapes decomposition.

It was discovered by Dr. Priestley, that when nitrous gas and oxygen

gas are mixed together in certain proportions, they instantly unite,

and are converted into nitrous acid. If this mixture be made over

water, the volume of the gases is instantly diminished, because the

nitrous acid formed loses its elasticity, and is absorbed by the

water. When nitrous gas is mixed with air containing oxygen gas, the

diminution of volume after mixture is greater the more oxygen gas is

present in the air. This induced Dr. Priestley to employ nitrous gas as

a test of the purity of common air. He mixed together equal volumes of

the nitrous gas and air to be examined, and he judged of the purity

of the air by the degree of condensation: the greater the diminution

of bulk, the greater did he consider the proportion of oxygen in the

air under examination to be. This method of proceeding was immediately

adopted by chemists and physicians; but there was a want of uniformity

in the mode of proceeding, and a considerable diversity in the results.

M. Lavoisier endeavoured to improve the process, in a paper inserted

in the Memoirs of the Academy, for 1782; but his method did not answer

the purpose intended: it was Mr. Cavendish that first pointed out an

accurate mode of testing air by means of nitrous gas, and who showed

that the proportions of oxygen and azotic gas in common air are

invariable.

Lavoisier, in the course of his investigations, had proved that

carbonic acid is a compound of carbon and oxygen; sulphuric acid,

of sulphur and oxygen; phosphoric acid, of phosphorus and oxygen;

and nitric acid, of nitrous gas and oxygen. Neither the carbon, the

sulphur, the phosphorus, nor the nitrous gas, possessed any acid

properties when uncombined; but they acquired these properties when

they were united to oxygen. He observed further, that all the acids

known in his time which had been decomposed were found to contain

oxygen, and when they were deprived of oxygen, they lost their acid

properties. These facts led him to conclude, that oxygen is an

essential constituent in all acids, and that it is the principle

which bestows acidity or the true acidifying principle. This was the

reason why he distinguished it by the name of oxygen.[5] These views

were fully developed by Lavoisier, in a paper inserted in the Memoirs

of the Academy, for 1778, entitled, "General Considerations on the

Nature of Acids, and on the Principles of which they are composed."

When this paper was published, Lavoisier's views were exceedingly

plausible. They were gradually adopted by chemists in general, and

for a number of years may be considered to have constituted a part of

the generally-received doctrines. But the discovery of the nature of

chlorine, and the subsequent facts brought to light respecting iodine,

bromine, and cyanogen, have demonstrated that it is inaccurate; that

many powerful acids exist which contain no oxygen, and that there is

no one substance to which the name of acidifying principle can with

justice be given. To this subject we shall again revert, when we come

to treat of the more modern discoveries.

[5] From ὀξυς, sour, and γινομαι, which he defined the _producer of

acids_, the _acidifying principle_.

Long as the account is which we have given of the labours of Lavoisier,

the subject is not yet exhausted. Two other papers of his remain to be

noticed, which throw considerable light on some important functions

of the living body: we allude to his experiments on _respiration_ and

_perspiration_.

It was known, that if an animal was confined beyond a certain limited

time in a given volume of atmospherical air, it died of suffocation,

in consequence of the air becoming unfit for breathing; and that

if another animal was put into this air, thus rendered noxious by

breathing, its life was destroyed almost in an instant. Dr. Priestley

had thrown some light upon this subject by showing that air, in which

an animal had breathed for some time, possessed the property of

rendering lime-water turbid, and therefore contained carbonic acid gas.

He considered the process of breathing as exactly analogous to the

calcination of metals, or the combustion of burning bodies. Both, in

his opinion acted by giving out phlogiston; which, uniting with the

air of the atmosphere, converted it into phlogisticated air. Priestley

found, that if plants were made to vegetate for some time in air that

had been rendered unfit for supporting animal life by respiration,

it lost the property of extinguishing a candle, and animals could

breathe it again without injury. He concluded from this that animals,

by breathing, phlogisticated air, but that plants, by vegetating,

dephlogisticated air: the former communicated phlogiston to it, the

latter took phlogiston from it.

After Lavoisier had satisfied himself that air is a mixture of oxygen

and azote, and that oxygen alone is concerned in the processes of

calcination and combustion, being absorbed and combined with the

substances undergoing calcination and combustion, it was impossible for

him to avoid drawing similar conclusions with respect to the breathing

of animals. Accordingly, he made experiments on the subject, and the

result was published in the Memoirs of the Academy, for 1777. From

these experiments he drew the following conclusions:

1. The only portion of atmospherical air which is useful in breathing

is the oxygen. The azote is drawn into the lungs along with the oxygen,

but it is thrown out again unaltered.

2. The oxygen gas, on the contrary, is gradually, by breathing,

converted into carbonic acid; and air becomes unfit for respiration

when a certain portion of its oxygen is converted into carbonic acid

gas.

3. Respiration is therefore exactly analogous to calcination. When air

is rendered unfit for supporting life by respiration, if the carbonic

acid gas formed be withdrawn by means of lime-water, or caustic alkali,

the azote remaining is precisely the same, in its nature, as what

remains after air is exhausted of its oxygen by being employed for

calcining metals.

In this first paper Lavoisier went no further than establishing these

general principles; but he afterwards made experiments to determine the

exact amount of the changes which were produced in air by breathing,

and endeavoured to establish an accurate theory of respiration. To this

subject we shall have occasion to revert again, when we give an account

of the attempts made to determine the phenomena of respiration by more

modern experimenters.

Lavoisier's experiments on _perspiration_ were made during the frenzy

of the French revolution, when Robespierre had usurped the supreme

power, and when it was the object of those at the head of affairs

to destroy all the marks of civilization and science which remained

in the country. His experiments were scarcely completed when he was

thrown into prison, and though he requested a prolongation of his

life for a short time, till he could have the means of drawing up a

statement of their results, the request was barbarously refused. He has

therefore left no account of them whatever behind him. But Seguin, who

was associated with him in making these experiments, was fortunately

overlooked, and escaped the dreadful times of the reign of terror: he

afterwards drew up an account of the results, which has prevented them

from being wholly lost to chemists and physiologists.

Seguin was usually the person experimented on. A varnished silk bag,

perfectly air-tight, was procured, within which he was enclosed, except

a slit over against the mouth, which was left open for breathing; and

the edges of the bag were accurately cemented round the mouth, by

means of a mixture of turpentine and pitch. Thus every thing emitted

by the body was retained in the bag, except what made its escape from

the lungs by respiration. By weighing himself in a delicate balance at

the commencement of the experiment, and again after he had continued

for some time in the bag, the quantity of matter carried off by

respiration was determined. By weighing himself without this varnished

covering, and repeating the operation after the same interval of time

had elapsed, as in the former experiment, he determined the loss of

weight occasioned by _perspiration_ and _respiration_ together. The

loss of weight indicated by the first experiment being subtracted from

that given by the second, the quantity of matter lost by _perspiration_

through the pores of the skin was determined. The following facts were

ascertained by these experiments:

1. The maximum of matter perspired in a minute amounted to 26·25 grains

troy; the minimum to nine grains; which gives 17·63 grains, at a

medium, in the minute, or 52·89 ounces in twenty-four hours.

2. The amount of perspiration is increased by drink, but not by solid

food.

3. Perspiration is at its minimum immediately after a repast; it

reaches its maximum during digestion.

Such is an epitome of the chemical labours of M. Lavoisier. When we

consider that this prodigious number of experiments and memoirs were

all performed and drawn up within the short period of twenty years,

we shall be able to form some idea of the almost incredible activity

of this extraordinary man: the steadiness with which he kept his own

peculiar opinions in view, and the good temper which he knew how to

maintain in all his publications, though his opinions were not only

not supported, but actually opposed by the whole body of chemists in

existence, does him infinite credit, and was undoubtedly the wisest

line of conduct which he could possibly have adopted. The difficulties

connected with the evolution and absorption of hydrogen, constituted

the stronghold of the phlogistians. But Mr. Cavendish's discovery, that

water is a compound of oxygen and hydrogen, was a death-blow to the

doctrine of Stahl. Soon after this discovery was fully established, or

during the year 1785, M. Berthollet, a member of the academy, and fast

rising to the eminence which he afterwards acquired, declared himself

a convert to the Lavoisierian theory. His example was immediately

followed by M. Fourcroy, also a member of the academy, who had

succeeded Macquer as professor of chemistry in the Jardin du Roi.

M. Fourcroy, who was perfectly aware of the strong feeling of

patriotism which, at that time, actuated almost every man of science

in France, hit upon a most infallible way of giving currency to the

new opinions. To the theory of Lavoisier he gave the name of _La

Chimie Française_ (French Chemistry). This name was not much relished

by Lavoisier, as, in his opinion, it deprived him of the credit which

was his due; but it certainly contributed, more than any thing else,

to give the new opinions currency, at least, in France; they became

at once a national concern, and those who still adhered to the old

opinions, were hooted and stigmatized as enemies to the glory of their

country. One of the most eminent of those who still adhered to the

phlogistic theory was M. Guyton de Morveau, a nobleman of Burgundy, who

had been educated as a lawyer, and who filled a conspicuous situation

in the Parliament of Dijon: he had cultivated chemistry with great

zeal, and was at that time the editor of the chemical part of the

Encyclopédie Méthodique. In the first half-volume of the chemical part

of this dictionary, which had just appeared, Morveau had supported the

doctrine of phlogiston, and opposed the opinions of Lavoisier with much

zeal and considerable skill: on this account, it became an object of

considerable consequence to satisfy Morveau that his opinions were

inaccurate, and to make him a convert to the antiphlogistic theory; for

the whole matter was managed as if it had been a political intrigue,

rather than a philosophical inquiry.