Elements of Chemistry

ANTOINE-LAURENT LAVOISIER

Elements of Chemistry

in a new systematic order, containing all the modern discoveries

TRANSLATED BY ROBERT KERR

WITH A NEW INTRODUCTION BY DOUGLAS MCKIE, D.SC, PH.D., F.R.S.E.

PROFESSOR OF THE HISTORY OF SCIENCE UNIVERSITY COLLEGE LONDON

DOVER PUBLICATIONS, INC

New York

Copyright

Copyright © 1965 by Dover Publications, Inc.

All rights reserved.

This Dover edition, first published in 1965, is an unabridged republication of the English translation first published by William Creech in 1790, to which has been added a new introduction by Douglas McKie, D. Sc, Ph. D., F.R.S.E., Professor of the History of Science, University College London.

International Standard Book Number

eISBN 13: 978-0-486-14125-1

Library of Congress Catalog Card Number 65-15513

Manufactured in the United States by Courier Corporation

64624607 2013

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Introduction to Dover Edition

The Elements of Chemistry, in a new systematic order, containing all the modern discoveries (Edinburgh, 1790), here reprinted in facsimile, is a translation by Robert Kerr (1755–1813) of the classic Traité élémentaire de Chimie, présenté dans un ordre nouveau et d’après les découvertes modernes (Paris, 1789) of Antoine-Laurent Lavoisier (1743–1794), the founder of modern chemistry. The Traité was first published in Paris in March 1789,¹ the Elements in Edinburgh in November 1790 in readiness for the opening of the university session of 1790-1791. That the English translation was published in Edinburgh was most appropriate; for Lavoisier’s great forerunner in these matters, Joseph Black (1728–1799), was still in active occupation of the chair of chemistry in the University of Edinburgh, lecturing to large classes in what was then the leading school of chemistry in the world, and had declared, with considerable effect on his colleagues and on his students, his acceptance of the revolutionary changes introduced by Lavoisier. Something, however, must be credited to the initiative of William Creech (1745–1815), who was then Scotland’s foremost publisher and from whose presses there poured forth a stream of literary as well as scientific works, including translations from several languages.

Robert Kerr, the translator, was a man of some reputation in Edinburgh. Born in Bughtridge, Roxburghshire, in 1755, the son of James Kerr, who had been Member of Parliament for Edinburgh from 1747 to 1754, he was related on his father’s side to the Royalist, Robert, first Earl of Ancrum (1578–1654); and his mother, Elizabeth Kerr, was a granddaughter of Robert, first Marquis of Lothian (1636–1703), a supporter of the glorious revolution of 1688 and a Privy Councillor to King William III. He was educated in Edinburgh, first at the High School, and then at the University where he studied medicine, attending the lectures of Joseph Black on chemistry in the sessions 1774–75, 1775–76, and 1776–77. Afterwards he became surgeon to the Orphan Hospital in Edinburgh. He was a man of broad scholarly gifts and his translations included not only the classic chemical treatise of Lavoisier, but also the Essay on the New Method of Bleaching (by means of chlorine) (Dublin [1790]; 2nd ed., Edinburgh, 1791) from the French of C.-L. Berthollet, The Animal Kingdom . . . Mammalia (London, 1792) from Part I of the Latin Systema Naturae of Linnaeus, The Natural History of Oviparous Quadrupeds and Serpents (Edinburgh, 1802) from the French of two volumes edited by Lacépède as posthumous additions to Buffon’s encyclopaedic Histoire Naturelle, and an Essay on the Theory of the Earth (Edinburgh, 1813, with four further editions in 1815, 1817, 1822, and 1825) from the French of Cuvier with additional notes by Robert Jameson (1774–1854), the distinguished mineralogist and Regius Professor of Natural History in the University of Edinburgh. Kerr compiled part of a series of volumes of A General History and Collection of Voyages and Travels. . . forming a complete history of the origin and progress of navigation, discovery and commerce, by sea and land, from the earliest to the present time (Edinburgh, 18 vols., 1811–1824); he wrote a General View of the Agriculture of the County of Berwick (London, 1809 and 1813) for the Board of Agriculture, and a History of Scotland during the reign of Robert I, surnamed the Bruce (Edinburgh, 2 vols., 1811); and he edited the Memoirs (Edinburgh, 2 vols., 1811) of William Smellie (1740–1795), printer, naturalist, antiquary, and first editor of the Encyclopedia Britannica. He was elected a Fellow of the Royal Society of Edinburgh in 1788 and of the Society of Antiquaries of Scotland. Kerr’s great abilities attracted him to science, and especially to chemistry, in which he had been instructed by Joseph Black, the pre-eminent teacher of his time, and he was well equipped to translate Lavoisier’s Traité.

Antoine-Laurent Lavoisier was born in Paris on Monday, 26 August 1743. His father, Jean-Antoine, was a lawyer, and so was his grandfather, but his earliest known ancestor was Antoine Lavoisier, who died in 1620, and who was a postillion in the King’s service at Villers-Cotterets, a small country town some fifty miles northeast of Paris; his mother was Émilie Punctis, daughter of Clément Punctis, advocate to the Parliament of Paris. There was wealth on both sides of the family. Lavoisier’s mother died when he was five years old, and he and his young sister, born in 1745, together with their father, went to live at the house of their widowed grandmother, Mme Punctis, where they were devotedly cared for by their aunt, their mother’s younger sister, Constance Punctis, then aged twenty-two. Lavoisier’s sister died in 1760 at the age of fifteen.

Lavoisier was educated in Paris at the Collège Mazarin, his father’s old school, from 1754 to 1760, and here he made his first acquaintance with science. But on leaving school he followed the family tradition and entered on the study of law, qualifying as Bachelor in 1763 and Licentiate in 1764. In these years of legal studies, however, he maintained and developed his interest in science, first aroused at school, learning geology from Jean-Étienne Guettard (1715–1786), Member of the Académie Royale des Sciences, the most eminent geologist in France, pioneer of geological surveys and of geological cartography and an intimate friend in the Punctis-Lavoisier home, and attending the inspiring lectures on chemistry given by another Academician, Guillaume-François Rouelle (1703–1770), at the Jardin du Roi. At the same time he studied astronomy and mathematics under Nicolas-Louis de Lacaille (1713–1762), botany under Bernard de Jussieu (1699–1777), both of them Academicians, and also anatomy; and he was much attracted to meteorology, recording the readings of the barometer in his home several times a day, an interest that later led him to organize such observations in other parts of France and in other countries with the object of discovering the laws relating to the movements of the atmosphere and thence devising rules for forecasting the weather.

But it was significantly to chemistry that Lavoisier turned with, however, some leanings towards geology and mineralogy through the influence of Guettard. The chemistry that he learned in the Jardin du Roi was very different from chemistry as he left it thirty years later; and to appreciate his reforms we need to consider, as briefly as we can, the state of that science in the mid-eighteenth century.

The long theoretical inheritance of chemistry was the four-element theory of the philosophers of Greek antiquity, according to which all substances were composed of the four elements, earth and air, fire and water, combined in an infinite variety of proportions. Each element had two qualities: earth was cold and dry, water was cold and wet, fire was hot and dry, and air was hot and wet. By adjustment of the qualities one element could be converted into another, according to this purely speculative idea; and, similarly, all substances were transmutable one into another by suitably adjusting the proportions of the universal four elements contained in each and all of them. Matter was a unity and substances were transmutable. The theory was not dead in Lavoisier’s time—in Edinburgh Black was teaching his classes that water was transmutable into earth.

Another theory of the composition of matter was put forward in the seventeenth century by Johann Baptista van Helmont (c. 1580–1644) in his posthumous Ortus medicinae (Amsterdam, 1648). He argued that all substances, except air, were ultimately derived from water. To demonstrate this he made his famous quantitative experiment with a small willow tree, an experiment that took five years, and he concluded that the tree had grown entirely from the water that he had supplied to it during this long period. His theory had one very great patron, Isaac Newton, who accepted it and referred to it in the Principia (London, 1687). His most significant work was, however, his recognition of the material nature of what he called gas, a generic name that he used for those products of chemical reactions that had been previously regarded as merely spirituous and immaterial; he explained to chemists that the many familiar and destructive explosions that shattered their glass apparatus when they experimented on reactions in sealed or closed vessels were due to the release of a wild spirit or gas. In a simple way he observed differences between gas from various sources but, as he did not isolate any gas, his distinctions were not precise, and he sometimes confused one gas with another. He had, however, advanced the chemistry of his time by demonstrating that these substances were material.

The more recent theory, the phlogiston theory, founded by Johann Joachim Becher (1635–1682) and developed by Georg Ernst Stahl (1660–1734), was to some extent derived from the old belief that there was a fire element; it applied to metals, minerals and combustible substances in general; and it supposed that all combustible bodies contained a common principle, that is, an element, which was named phlogiston and which was released in the process of combustion in the form of fire, flame and, sometimes, light. That combustion could proceed only to a limited degree in a confined volume of air, a fact long familiar to generations of observers, was accordingly explained by asserting that a limited amount of air could take up only a limited amount of the phlogiston released from a substance subjected to combustion; a similar explanation was advanced for the corresponding and well-known fact that respiration ceased and animal life was likewise extinguished in a limited amount of air, respiration being considered as resembling combustion and releasing phlogiston. The proportion of phlogiston in different combustibles varied widely. Bodies that resisted the action of fire and those that would not burn contained very little or none at all. On the other hand, charcoal, oils, fats, spirit of wine, wheat, flour, must be composed entirely or almost entirely of phlogiston, since it was observed that on burning they either completely disappeared or left negligible residues.

The application of the phlogiston theory to metals had important consequences. It had long been known that when metals were heated in air they lost their metallic properties and were changed into powders or, as they were called, calces (literally, ashes); and it was equally well known, long before the phlogiston theory was formulated, that the calces of metals on heating with charcoal were reconverted into the original metals, recovering all their metallic properties, their form, and their lustre. Therefore, it appeared, the restoration of phlogiston to the calx reconstituted the metal from which it had been formed, and the metals, like combustible bodies, contained this same common constituent, phlogiston, which, it will be seen, could now be demonstrably transferred from charcoal to calx, that is, from one substance to another. Phlogiston could not, however, be isolated, put in a bottle and labelled, but neither could electricity; yet the existence of phlogiston was satisfactorily established in the minds of the chemists of that age by these and by many other observations. The theory was applied to explain both the chemical properties of substances and chemical changes in general. Chemistry was, indeed, systematized in terms of this theory; and, erroneous as it proved to be, it brought about a great change in chemical thought, which is too infrequently emphasized; for, whereas the old theory of the four elements or even its variant, the three principles of Paracelsus (1493–1541), which we have not space to consider in detail here, was merely a theory of the elementary chemical composition of matter, the phlogiston theory could be applied to explain chemical changes, not merely chemical composition, and it could be and was applied to explain and even to systematize the vast, but hitherto disorderly, and ever-increasing knowledge of chemical reactions and chemical processes. The phlogiston theory was thus the first great and systematizing generalization in chemistry. It was wrong; but it was accepted almost without exception by all the leading chemists of eighteenth-century Europe, whose distinguished names are too many to enumerate here; and, if there is one thing more than others to be said in favour of scientists, it is that their history shows that they learn from their mistakes.

The phlogiston theory was, however, in spite of its success and its acceptance, being slowly and imperceptibly undermined even before Lavoisier turned the synthetic powers of his genius to the reconsideration of chemical phenomena. Already a century earlier, Robert Boyle (1627–1691), in his Sceptical Chymist (London, 1661), had destructively criticized the four-element theory together with the Paracelsian theory of the three principles on the simple basis that neither theory was in agreement with the facts of chemistry. Chemists, of course, considered that fire resolved all substances into their elements, but Boyle pointed out that the number of products varied according to the means by which fire was applied, either on an open hearth or by distillation in a retort. He mentioned as a notable instance that wood heated in the open gave ashes and soot, but fired in a retort it yielded oil, spirit, vinegar, water, and charcoal, and therefore, according to the method of heating, the same substance gave either two or five products, which was either one less than the three principles of the recent Paracelsus or one more than the four elements of the ancient Greeks. Moreover, if one took a substance prepared from known ingredients, such as soap, made from fat and alkali, treatment with fire did not reproduce those ingredients, but two very different products which were, Boyle pointedly added, quite useless for making soap. Fire, he said, did not decompose substances into their elements, as the facts of chemistry plainly showed, but, on the contrary, rearranged their component particles to form different compounds. Chemists, he urged, should reconsider the many experiments they had made and also devise new ones; and, to help towards a solution of the problem of what constituted a chemical element, he formulated an entirely new definition, which, stripped of its cumbersome seventeenth-century phraseology, defined an element as a substance that cannot be decomposed into any simpler substance. It was this definition that Lavoisier eventually revived more than a hundred years later. In the meantime, however, while Boyle’s criticism of the accepted theory of chemical elements had been destructive, chemists continued to make use of either the four elements or the three principles or even of both, for want of a better theory; and they did not treat the problem very seriously. Often dismissing it briefly in their books, they were more concerned with describing the preparation and properties of substances. Boyle also maintained that it was too simple to assume that the great book of Nature, still to be regarded as written in cipher, could be decoded on the supposition that it was written in four characters only; there might well be neither three nor four but, more probably, a far greater number of chemical elements.

In another direction, Boyle, in his researches on air, opened a new field of investigation that eventually led by very indirect ways to the closer chemical study of a substance, namely, air, long considered to be unquestionably an element. In the air pump constructed for him by Robert Hooke (1635–1703) he carried out experiments both on combustion and on respiration, reported in his New Experiments Physico-Mechanicall (Oxford, 1660), finding that both fire and life were extinguished much more rapidly when the air was pumped out of the receiver of the pump into which various burning substances and small animals had been placed in turn; while he knew that in the open air both processes persisted, he felt that he could conclude only that air supported fire and life in some way not understood. His contemporary, Hooke, went, however, much further, arguing in his Micrographia (London, 1665) that since certain combustible mixtures containing saltpetre would burn under water, that is, in the absence of air, it followed that the common air and the substance saltpetre each contained a component that supported combustion. Both Boyle and Hooke returned to this problem on a number of occasions, far too many to recount here. Boyle in 1670 reported to the Royal Society that air was not diminished in respiration, since he could detect no reduction in pressure when he placed a mouse and then a bird in the air in a sealed glass vessel together with a mercury pressure-gauge; and in some Tracts (London, 1674) he claimed, after experiments in a glass vessel with the flame of lamps burning either oil or spirit of wine, that combusion similarly did not diminish air.² Hooke in the previous year, 1673, had reported to the Royal Society an experiment that showed air to be decreased by combustion, but he was unable to repeat this experiment before the Society. Boyle went only so far as to conclude, on the evidence before him, that common air contained a minute proportion of some vital substance that supported fire and life. At this same time John Mayow (1641–1679), in his Tractatus quinque (Oxford, 1674), changed the current experimental technique, putting burning combustibles (such as a lighted candle) and small animals (mice), not in air contained in sealed glass vessels, but in air confined over water, and thereby showed that air was decreased both by combustion and by respiration.³ His results, however, appear to have had no effect on the further exploration of the problem by his contemporaries. So ended many years of experiment and discussion; but it is to be noted that all three of these able experimenters had concluded that air contained something that supported combustion and respiration, although to Boyle this substance was present in only a minute proportion.⁴ The study of the phenomena of the calcination of metals, by which the problem of the composition of the air was finally resolved by Lavoisier a century later, played no significant part in these seventeenth-century studies on combustion, although Mayow had asserted that in calcination metals took up nitro-aereal particles from the air; for, while Boyle had in his Essays of Effluviums (London, 1673) established once and for all in a long series of experiments the important experimental result that metals gained in weight on calcination, he had ascribed this increase of weight to the addition of material particles of fire that had become corporified with his metals.⁵

Boyle had also made another great change in chemical thought by applying the ancient Greek atomic theory of Democritus to chemical changes. According to this theory the material world consisted of atoms and void. The atoms were minute, indestructible, eternal; they were all qualitatively the same; and their arrangements in different numbers and in different configurations produced the confusing variety of different substances in the world. This mechanical philosophy, as it was termed, had recently been brought into greater prominence by the work of Pierre Gassend (1592–1655) and Boyle had applied it throughout his chemical studies. If matter had such a structure, one substance could, therefore, be changed into another by the mere reordering of its particles into a new configuration. Thus the unity and the transmutability of matter were alike implicit in the atomic theory and in the four-element theory. But Boyle and his like-minded contemporaries are not on that account to be inconsiderately dubbed alchemists; for the objective of the alchemists was to adjust the proportions of the four qualities and the four elements, not to rearrange atoms in new configurations. Isaac Newton (1642–1727), having followed Boyle in accepting the old atomic theory, and accepting it even more completely than Boyle, wrote in his Opticks (London, 1717, 2nd ed., Query 30) that dense, that is, solid, bodies could be rarefied into air, and this air reconverted into a solid. Newton’s comment was taken up later by Stephen Hales (1677–1761) in his Vegetable Staticks (London, 1727). Hales heated weighed amounts of various substances and collected the air that was released from them in the process; unlike Newton, however, he supposed that the air existed as air in the bodies from which he obtained it, but he had demonstrated that air was widely contained in many different bodies or, as he said, fixed in them. For his experiments Hales devised an early form of gas-collecting apparatus, an apparatus in which the receiver for collecting the product was separated from the part where the air was produced, the two components being connected by a delivery tube. This was an important practical improvement in apparatus. Boyle had earlier described in his New Experiments of 1660, referred to above, a simple method of collecting air produced by the action of acids on metals. It consisted merely of a phial, filled with dilute acid and inverted in a bowl containing water, the metal being inserted into the phial in small pieces just before inversion. Boyle did not give an illustration of this apparatus, but it was subsequently illustrated in Mayow’s Tractatus of 1674. Both Boyle and Mayow obtained hydrogen and nitric oxide in this way and each supposed that he had obtained air, "air regenerated de novo." Neither with Hales nor with his predecessors was there any suspicion that there might exist different airs, or, as we would now say, gases. Hales had, however, made an interesting observation, namely, that burning phosphorus and also burning sulphur absorbed a considerable quantity of air.

In the second half of the eighteenth century, further significant advances came somewhat less slowly. In 1754 Joseph Black presented for the degree of M.D. in the University of Edinburgh a dissertation⁶ in the customary Latin on the acid humour arising from food and on magnesia alba, a new drug recently introduced into medicine; he read an enlarged account of this a year later to a society that subsequently became in 1783 the Royal Society of Edinburgh, and this was published in 1756.⁷ In this extension of his medical dissertation Black concluded from his experiments that magnesia alba and other alkaline substances in the mild state contained what he called, following the example of Hales, fixed air, whereas in the caustic state they did not contain this air. Moreover, he carried chemistry forward at one stride by showing that fixed air was chemically different from common air. Black had traced by means of the balance the changes in the mild alkalis produced by the action of heat in converting them into their caustic form. He did not isolate fixed air (our modern carbon dioxide), but he showed later in his lectures that it was produced in the combustion of charcoal, in the burning of a candle, in respiration, and in fermentation. Thus for the first time an air had been chemically differentiated from the common air of the atmosphere. Ten years later, in 1766, Henry Cavendish (1731–1810) isolated inflammable air (hydrogen) and studied its chemical and physical properties.⁸ Then in 1772 Daniel Rutherford (1749–1819) showed that, after the removal of fixed air from air vitiated by the respiration of mice or by the combustion of coals, there was a residue of another mephitic air, which he called noxious air (nitrogen), and which was also obtained, he added, as a residue from air after the burning of sulphur or phosphorus and by the calcination of metals.⁹ Between 1772 and 1777 Joseph Priestley (1733–1804) greatly enlarged this new field of research by the isolation and recognition of seven other new airs, namely, nitrous air (nitric oxide), acid air or muriatic acid air (hydrogen chloride), alkaline air (ammonia), diminished nitrous air (nitrous oxide), vitriolic acid air (sulphur dioxide), dephlogisticated air (oxygen) and nitrous acid vapour (nitrogen dioxide).¹⁰

One of Priestley’s discoveries was of particular significance at this time and it needs some detailed notice here. On 1 August 1774 he obtained a new air by heating mercurius calcinatus per se (mercuric oxide, prepared by heating mercury). It had unusual properties; while it was not soluble in water, it greatly enhanced the flame of a candle. His experiments were interrupted by a journey to the Continent. In Paris in November 1774 he met Lavoisier and other men of science associated with him and he told Lavoisier of his most recent discovery. Priestley’s reputation was already high in Paris; he was a Fellow of the Royal Society of London; and a year earlier, on 30 November 1773, he had been awarded the Copley Medal, the highest award in the Society’s gift, for the paper on airs that he had published in 1772 in the Philosophical Transactions.¹¹ After his return to England he resumed his experiments and in March 1775 he discovered that his new air was respirable, even more respirable than atmospheric air since it was far less rapidly and far less extensively vitiated by respiration; likewise it was a far better supporter of combustion. Thinking on these things, Priestley named it dephlogisticated air, because, since it was such a remarkable supporter of combustion and of respiration, it must be free of the phlogiston that was always present in considerable proportions in the common air of the atmosphere into which it was being uninterruptedly poured from fires, from breathing animals, and from fermentations.¹² Thus, the new air was common air freed from the phlogiston that it normally contained. This information was of the greatest interest to Lavoisier, to whose early work we now turn.

Before doing so, however, we may remind ourselves that when Lavoisier embarked on his first researches in chemistry the four-element theory was generally, though often tacitly, accepted or rather not rejected for want of a better one; that Boyle’s definition of the chemical element had fallen dead from his hands over a century earlier; that both combustion and the calcination of metals were regarded as processes of decomposition; that the chemical compositions of air and of water were unknown and even unsuspected, as also were those of the vast array of other less common and less familiar substances; and that the phlogiston theory dominated chemistry. Within twenty years Lavoisier changed all this.

After his studies under Guettard, Rouelle, and the other Academicians whom we have mentioned, Lavoisier worked for three years with Guettard on the collection of details for the projected geological map of France, and in the summer of 1767 he accompanied Guettard on a geological survey of Alsace and Lorraine. In 1764 he submitted a memoir to the Académie Royale des Sciences on the properties of gypsum and the setting of plaster of Paris; it was his first contribution to chemistry and it was a careful and exact research. Other memoirs followed. In 1765 he submitted an essay in a competition organized by the Academy on the problem of lighting the streets of cities and large towns at night. He did not win the prize; but he was specially awarded a gold medal by the King for this remarkable study, which included not only many scientific experiments but also an economic analysis of costs. He continued his geological field work and at this time he seems to have finally decided to abandon the profession of law for the pursuit of science. In 1768, at the early age of twenty-five, he was elected a member of the Academy of Sciences in the junior grade of assistant. Earlier in that year he entered the Tax-Farm as an Assistant Farmer-General, in its dismal consequences the most ill-fated action in his life; he had recently inherited the fortune left to him by his mother and he wished to invest it and use the income to enable him to devote as much of his time as possible to scientific research. In 1771 he married Marie-Anne-Pierrette, daughter of the Farmer- General Jacques Paulze. Madame Lavoisier was an able and well-educated woman. She learned English to help her husband in his reading of the growing mass of scientific literature, for which he lacked adequate time on account of his heavy administrative duties in the Tax-Farm and his many prolonged absences from Paris on journeys of supervision and inspection in the provinces; she also helped him in his experiments, recording observations and results in his laboratory notebooks and drawing sketches of his apparatus; and she drew the diagrams for the thirteen folding plates of his Traité.

As Lavoisier entered more actively into the scientific life of Paris, there was much discussion about the improvement of the supply of drinking water of good quality to the city. During his field work with Guettard he had determined with hydrometers and recorded the densities of the waters of rivers and springs and even of the water supplied at the inns at which they stayed. He used this physical means because there was no chemical method for ascertaining the purity of water. Moreover, as it was still generally accepted that water on heating was converted, at least in part, into earth, the solution of the problem of the analysis of water did not seem at all promising since, if this belief were well founded, the water itself would be slowly and constantly changing into earth during the investigation, which would inevitably be confusing. After studying all that had been published on the conversion of water into earth, Lavoisier concluded that what had been done was not satisfactory and decided that further experiment was necessary. Influenced by Boyle’s method of studying the calcination of metals in sealed vessels, from 24 October 1768 to 1 February 1769 he heated a weighed amount of water, as pure as could be obtained by repeated distillation, in a weighed sealed glass vessel, the alchemist’s pelican, in which a liquid could be continuously distilled on itself. At the end of this long experiment, the total weight of the unopened vessel and its contents was the same as it was at the beginning of the experiment over a hundred days previously. That he had Boyle’s experiments in mind is clear, because his immediate conclusion at this stage of the research was that no material particles of fire or of any other external matter had penetrated the glass walls of the pelican. He then weighed the pelican after opening it and pouring the contents into another glass vessel. Some earth had been formed and particles of it were visible in the water. However, he found that the weight of the pelican had decreased by an amount nearly equal to the weight of the earth obtained, and therefore the earth had been produced by the disintegrating erosive action of the water on the glass fabric of the pelican, not by the conversion of water into earth. In the chemical context of the time, this was a most striking result; and a theory held for twenty centuries and still accepted by many of his contemporaries had been refuted by this patient and difficult research, well designed and skilfully performed.

Early in 1772 Lavoisier collaborated with some of his colleagues in the Academy in a series of experiments with the great burning-lens of Tschirnhausen, owned by the Academy, on the question of whether the diamond was combustible. The results showed that the diamond was unaffected by heat if protected from access to the air. Further experiments with another of Tschirnhausen’s burning-lenses showed that the diamond was combustible. Later in 1772 he experimented on the combustion of phosphorus and of sulphur. On 20 October he sent a note to the Academy stating that phosphorus absorbed air in burning, that it combined with air to produce acid spirit of phosphorus (phosphoric acid), and that it increased in weight by this combination with air. Twelve days later, on 1 November, he deposited a sealed note with the Secretary of the Academy, which was not to be opened until he so desired. In this historic document he stated that he had discovered that both sulphur and phosphorus did not lose but, on the contrary, gained weight on burning; that these increases in weight arose from the combination of sulphur and of phosphorus with a prodigious quantity of air; that what he had discovered with regard to the combustion of sulphur and of phosphorus might well occur in all substances that gained in weight in combustion and in calcination; and that, by the reduction of the calx of lead with charcoal, he had found that a large quantity of air was liberated, a thousand times greater in volume than the quantity of calx that he had used, which result, he claimed, completely confirmed his conjecture. Hales, it will be recalled, had observed that both burning phosphorus and burning sulphur absorbed a considerable amount of air, an observation slight in importance and in significant detail as compared with that now reported by Lavoisier.

Three months later Lavoisier wrote in his laboratory notebook on 20 February 1773 that he intended to make many experiments on the air that combined with substances or was liberated from them, an immense series of experiments, he wrote, destined to bring about a revolution in physics and in chemistry. As a beginning of this plan, he repeated the experiments made by Black and others and published his results in a volume entitled Opuscules physiques et chymiques (Paris, 1774). The book was published in January 1774. At the conclusion of this long research, Lavoisier was not quite sure whether it was Black’s fixed air that combined with the metals in calcination, but he was more inclined to believe that it was common air or some elastic fluid (a gas, as we would now say) contained in common air; his reasons for this latter conclusion were that metals could not be calcined in vessels exhausted of air, that the calcination was greater when a greater surface of metal was exposed to the air, and that an elastic fluid was released when metallic calces were reduced to metals by heating with charcoal. Further, he found that the elastic fluid produced by heating the calces with charcoal was