450 



NA TURE 



[September 4, 1890 



his earlier experiments, and claimed, not only the discovery of 

 oxygen, but ail that Lavoisier deduced from it. " But," says M, 

 Berthelot, in reference to this circumstance, " his contemporaries 

 paid little heed to his pretensions, nor will posterity pay more " 

 ("La Revolution Chimique," p. 60). 



M. Berthelct, however, does not dismiss Lavoisier's claims to 

 a participation in the discovery in the same summary fashion. 

 On the contrary, whilst not explicitly claiming for him the actual 

 isolation, in the first instance, of oxygen, the whole tenor of his 

 argument is to extenuate, and even to justify, his demand to be 

 regarded as an independent discoverer of the gas. He begins by 

 asserting that Lavoisier had already a presentiment of its ex- 

 istence in 1774, and he quotes, in support of this assumption, an 

 abstract from Lavoisier's memoir, published in December 1774, 

 mihe Journal de Physique of the Abbe Rozier : "This air, 

 deprived of its fixable portion (by metals during calcination), is 

 in some fashion decomposed, and this experiment would seem to 

 afford a method of analyzing the fluid which constitutes our 

 atmosphere, and of examining the principles of which it is com- 

 posed. ... I believe I am in a position to affirm that the air, 

 as pure as it is possible to suppose it, free from moisture and 

 from every foreign substance, far from being a simple body, or 

 element, as is commonly thought, should be placed, on the con- 

 trary, ... in the group of the mixtures, and perhaps even in 

 that of the compounds." 



M. Berthelot further asserts that Lavoisier was at this time 

 the first to recognize the true character of air, and he expresses 

 his belief that it is probable that he would himself have suc- 

 ceeded in isolating its constituents if the path of inquiry had 

 been left to him alone. It is no disparagement to Lavoisier's 

 prescience to say that there is nothing in these lines, nor in the 

 memoir of the repetition of Boyle's experiments on the calcina- 

 tion of tin to which they refer, to show that Lavoisier had made 

 any advance beyond the position of Hooke and Mayow. It has 

 been more than once pointed out that the chemists of the seven- 

 teenth century understood the true nature of combustion in air 

 ranch better than their brethren of the last quarter of the eight- 

 eenth century. Hooke, in the " Micrographia," and Mayow, in 

 his " Opera Omnia Medicophysica," indicated that combustion 

 consists in the union of something with the body which is being 

 burnt ; and Mayow, both by experiment and inference, demon- 

 strated in the clearest way the analogy between respiration and 

 combustion, and showed that in both processes one constituent 

 only of the air is concerned. He distinctly stated that, not only 

 is there increase of weight attending the calcination of metals, 

 but that this increase is due to the absorption of the same 

 spiritus from the air that is necessary to respiration and combus- 

 tion. Mayow 's experiments are so precise, and his facts so in- 

 contestable, that, as Chevreul has said, it is surprising that the 

 truth was not fully recognized until a century after his researches 

 (vide Watts's "A Dictionary of Chemistry," by Morley and Muir, 

 Art. " Combustion," p. 242). 



It is now necessary to examine Lavoisier's claims rather more 

 closely and in the light of M. Berthelot's book. A resume of 

 his work " On the Calcination of Tin " was given by Lavoisier to 

 the Academy in November 1774, but the complete memoir was 

 not deposited until May 1777. A careful comparison of an ab- 

 stract of what was stated to the Academy in November 1774, 

 contributed by Lavoisier himself, in December I774> to the 

 Journal de Physique of the Abbe Rozier, makes it evident 

 that very substantial additions were made to the communication 

 before it was finally printed in the Memoires de l^Acadimie des 

 Sciences. The possibility of this is allowed by M. Berthelot. 

 He says: — "A summary communication, often given viva 

 voce to a learned Society, such as the Academy of Sciences of 

 Paris or the Royal Society of London, would immediately call 

 forth verifications, ideas, and new experiments, which would de- 

 velop the range and even the results of such communication. 

 The original author, when printing his memoir, would in return 

 — and for this he is hardly blamable — embody these additional 

 results and later interpretations. It thus becomes most difficult 

 to assign impartially to each his share in a rapid succession of 

 discoveries" {loc. cit., p. 58). 



But although, as we shall see, Lavoisier was certainly aware 

 of Priestley's great discovery, no allusion is made to the gas, nor 

 to Priestley's previous work on the other constituent of air, which 

 is printed in the Philosophical Transactions for I772> a-nd for 

 which he was awarded the Copley Medal by the Royal Society. 

 It is simply impossible to believe that Lavoisier could have been 

 uninfluenced by this work. Indeed, we venture to assert that 



NO. 1088, VOL. 42] 



the full and clear recognition of the non-elementary nature of the 

 air which he eventually made was based upon it. It is note- 

 worthy that in the early part of his memoir he states his opinion 

 that the addition, not only of powdered charcoal, but of any 

 phlogistic substance to a metallic calx is attended with the form- 

 ation of fixed air. It is certain that at this period he had not 

 only not consciously obtained any gas resembling Priestley's 

 dephlogisticated air from any calx with which he had experi- 

 mented, but that none of his experiments had afforded him any 

 idea that the gas absorbed during calcination was identical 

 with it. 



At Easter 1775, Lavoisier presented a memoir to the Academy 

 " On the Nature of the Principle which Combines with Metals 

 during Calcination." This was "r^/w /^ 8 a^J/, 1778." To the 

 memoir there is a note stating that the first experiments detailed 

 in it were performed more than a year before ; those on the red 

 precipitate were made by means of a burning-glass in the month 

 of November 1774, and were repeated in the spring of 1775 at 

 Montigny in conjunction with M. Trudaine. In this paper 

 Lavoisier first distinctly announces that the principle which 

 unites with metals during their calcination, which increases 

 their weight, and which transforms them into calces, is nothing 

 else " than the purest and most salubrious part of the air ; so that 

 if that air which has been fixed in a metallic combination again 

 becomes free, it reappears in a condition in which it is eminently 

 respirable, and better adapted than the air of the atmosphere 

 to support inflammation and the combustion of substances" 

 (" Qiuvres de Lavoisier," official edition, vol. ii. p. 123). He 

 then describes the method of preparing oxygen by heating the 

 red oxide of mercury, and compares its properties with those of 

 fixed air. There is, however, no mention of Priestley, nor any 

 reference to his experiments. It can hardly be doubted that in 

 this memoir Lavoisier intended his readers to believe that he 

 was ' ' the true and first discoverer " of the gas which he afterwards 

 named oxygen. This is borne out by certain passages in his 

 subsequent memoir " On the Existence of Air in Nitrous Acid ; 

 lu le 20 avril, 1776, remis en dece7nbre 1777." He had occasion 

 incidentally to prepare the red oxide of mercury by calcining the 

 nitrate, and says that he obtained from it a large quantity of an air 

 " much purer than common air, in which candles burnt with a 

 much larger, broader, and more brilliant flame, and which in no 

 one of its properties differed from that which / had obtained 

 from the calx of mercury, known as mercuritts precipitatus per 

 se, and which Mr. Priestley had procured from a great number of 

 substances by treating ihem with nitric acid." 



In another part of this memoir he says that " perhaps, strictly 

 speaking, there is nothing in it of which Mr. Priestley would 

 not be able to claim the original idea ; but as the same facts 

 have conducted us to diametrically opposite results, I trust that, 

 if I am reproached for having borrowed my proofs from the 

 works of this celebrated philosopher, my right at least to the 

 conclusions will not be contested." M. Berthelot remarks on 

 the irony of this passage : we may infer from it that the friends 

 of the English chemist had not been altogether idle. In his 

 memoir " On the Respiration of Animals," read to the Academy 

 in 1777, he again appears to admit the claim of Priestley to at 

 least a share in the discovery : " It is known from Mr. Priestley's 

 and my experiments that tnercurius precipitatus per se is nothing 

 but a combination," &c. In several subsequent communications 

 Priestley's name is mentioned in very much the same connection, 

 until we come to the classical memoir " On the Nature of the 

 Acids," when it is said : " I shall henceforth designate the de- 

 phlogisticated air, or the eminently respirable air, ... by the 

 name of the acidifying principle, or, if it is preferred to have the 

 same signification under a Greek word, by that of the ' principe 

 oxygine,' " 



In none of the memoirs after that of Easter 177S is the claim 

 for participation more than implied ; it is made explicitly for the 

 first time in the paper " On the Method of Increasing the Action 

 of Fire," printed in the Memoires de I' Academic for 1782,. 

 and in these words : — " It will be remembered that at the meeting 

 of Easter 1775 I announced the discovery, which I had made 

 some months before with M. Trudaine, ^ in the laboratory at 

 Montigny, of a new kind of air, up to then absolutely unknown,, 

 and which we obtained by the reduction of tnercurius precipi- 

 tatus per se. This air, which Mr. Priestley discovered at very 

 nearly the same time as I, and I believe even before me, and 

 which he had procured mainly from the combination of minium 



' M. Trudaine de Montigny died in 1777. 



