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Nov. 2, 1882] 
NATURE 5 
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.” 
Had Dr. Thomson been better acquainted with the 
character of Lavoisier; had he known what manner of 
man he was in all his dealings with his contemporaries and 
with the work of those who had gone before, he would 
never have made such an assertion as the above. 
Prof. Liuxley in his Birmingham address on Priestley 
(August 1, 1874) also accuses Lavoisier of unfairness : 
“though Lavoisier,’ he writes, “undoubtedly treated 
Priestley very ill, and pretended to have discovered 
dephlogisticated air, or oxygen, as he called it, inde- 
pendently, we can almost forgive him, when we reflect 
how different were the ideas which the great French 
chemist attached to the body which Priestley discovered.” 
Starting, as we confess, with the complete belief that 
Lavoisier did not discover oxygen, we are compelled to 
assert that a careful perusal of the various memoirs 
bearing upon the subject and the consistent attitude of 
Lavoisier throughout, has led us to the firm conviction 
that he has as much right to be regarded as the discoverer 
as either Priestley or Scheele. 
Let us examine Dr. Thomson’s statements. The year 
1774 he asserts “‘is a considerable time before the date 
assigned by Lavoisier to his pretended discovery.” 
Lavoisier (‘‘ Traité élémentaire de Chimie,” 1789, part 
1, Chap. III.) says in speaking of oxygen : “ Cette air que 
nous avons découvert presque en méme temps, M. Priest- 
ley, M. Scheele, et moi, a été nommé, par le premier air 
déphlogistiqué; par le second, air empyréal. Je lui 
avais d’abord donné lenom d’air éminemment respirable ; 
depuis on y a substitué celui dazy vital.’ Evidently 
“presque en méme temps’’ is a very loose statement. 
Scheele’s treatise, “Chemische Abhandlungen von der 
Luft und TFeuer,’’ was published in Upsala in 1777, and 
he certainly did not discover oxygen before 1775. 
Lavoisier is therefore speaking in quite general terms 
when he says that oxygen was discovered almost at the 
same time by Priestley, Scheele, and himself. He at 
least puts himself on a level with Scheele as to date, and 
it is universally admitted that Scheele procured the gas 
after Priestley. And this general expression is the only 
claim to the discovery we can anywhere find in the 
writings of Lavoisier. 
Now what are the facts in favour of Lavoisier? 
On November 1, 1772, he deposited with the secre- 
tary of the Academy a note, which was opened on 
May 1 following, in which he stated that he had dis- 
covered that sulphur and phosphorus, instead of losing 
weight when burnt, actually gained it, without taking into 
account the humidity of the atmosphere. He traced this 
to the fixation of air during the combustion, and surmised 
that the gain of weight by metals during calcination was 
due to the same cause. He reduced litharge in close 
vessels ‘‘avec lappareil de Hales,’’ and observed the 
disengagement of a great quantity of air. ‘‘This note 
leaves no doubt,’’ says Dr. Thomson, ‘‘that Lavoisier 
had conceived his theory, and confirmed it by experi- 
ment, at least as early as November, 1772. . . . “ [Il est 
aisé de voir,” writes Lavoisier, just before his death, “ que 
Javais concu, dés 1772, tout ’ensemble du systéme que 
J'ai publié depuis sur le combustion.’’ 
Early in 1774 he published experiments in his “ Opus- 
cules physiques et chimiques,” to prove that lead and 
tin, when heated in closed vessels, gain weight, and 
cause a diminution in the volume of air. ‘‘J’ai cru pou- 
voir conclure,” he writes, “de ces expériences, qu’une 
portion de lair lui-méme, ou d’une matiére quelconque, 
contenue dans l’air, et qui y existe dans un état d’élasticité, 
se combinait avec les metaux pendant leur calcination, et 
que c’etait 4 cette cause qu’était due l’augmentation 
de poids des chaux métalliques.’’ Later in the year he 
read before the Academy (‘a la rentrée publique de la 
Saint Martin, 1774”); a memoir ‘‘On the calcination of 
tin in closed vessels,” in which he proved that when tin 
was calcined in hermetically sealed vessels, it absorbed a 
portion of the air equal in weight to that which entered 
the retort when it was unsealed, so as to admit air. 
He states as his conclusion that only a part of the air 
can combine with metals or be used for purposes of 
respiration, and that hence the air is not a simple body as 
generally believed, but composed of different substances ; 
and he adds that his experiments on the calcination of 
mercury, and the revivification of the calx, singularly con- 
firm him in this opinion. 
At the Easter Meeting of the Academy in 1775, 
Lavoisier read a memoir, “Sur la nature du principe qui 
se combine avec les métaux pendant leur calcination et 
qui en augmente en poids.” Ina footnote we are informed 
that the first experiments described in the memoir were 
made more than a year previously, while those relating tothe 
mercury precip~itatus per se,“ ont dabord été tentées au 
verre ardent dans le mois de Novembre, 1774.’ Having 
heated calx of mercury with carbon, he found that fixed 
air soluble in water was given off, while when he heated 
it alone he observed avec beaucoup de surprise that an air 
was produced insoluble in water, readily supporting com- 
bustion, serving for the calcination of metals; incapable of 
precipitating lime water, and incapable of being absorbed 
by alkalies, 
Priestley obtained a gas from mercury, calcinatus per 
se,on August I, 1774, and finding it insoluble in water, 
and capable of readily supporting combustion, concluded 
that the mercury during calcination had absorbed wztrvous 
particles from the air. He did not discover the real 
nature of the gas till March, 1775. In October, 1774, 
Priestley visited Paris, and mentioned to Lavoisier, 
Leroy, and others the prodction of gas from the mercury 
calcinatus per se. Probably the properties were not 
demonstrated. Lavoisier says he observed “with much 
surprise” that the gas was not absorbed by water, &c., 
was not in fact fixed air. He had expected to find the 
air given off by calx of mercury when heated alone, the 
same as that evolved when he tested it with charcoal, and 
was surprised to find it a different air. He enumerates 
the principal properties of the new gas as we know it. 
He burns it in a candle, charcoal, and phosphorus. He 
calls it air emdnemment respirable, and atr pur; and says 
it alone is concerned in respiration, combustion, and the 
calcination of metals. 
Lavoisier constantly quotes Priestley and Scheele in 
connection with oxygen ; again and again he speaks ot 
that air which Mr. Priestley calls dephlogisticated, M. 
Scheele emfyreal, and 1 highly-respirable,’” but we can 
find no distinct claim to its discovery save the sentence 
quoted above, in which he states that it was discovered 
almost at this same time by Priestley, Scheele, and 
himself. 
In his next memoir, ‘On the Existence of Air in 
Nitrous Acid” (read April 20, 1776), he says: “Je com- 
mencerai, avant d’entrer en matiére, par prévenir le public 
qwune partie des expériences contenues dans ce mémoire 
ne m’appartiennent point en propre; peut-Ctre méme, 
rigoureusement parlant, n’en est-il aucune dont M. 
Priestley ne puisse réclamer la prémiére idée.” And again : 
“Je terminerai ce mémoire comme je ]’ai commencé, en 
rendant hommage & M. Priestley de la plus grande partie 
de ce qu’il peut contenir d’interessant.’’ Moreover, in 
giving an account of ammonia, sulphurous acid, and 
several other gases, he writes: “ Les expériences dont je 
vais rendre compte appartiennent presque toutes au doc- 
teur Priestley; je n’ai d’autre mérite que de les avoir 
répétées avec soin, et surtout de les avoir rangées dans 
un ordre propre & presenter des consequences.”’ Thus 
it must be admitted that Lavoisier was always ready to 
acknowledge the merits of Priestley. 
Even supposing that Priestley had demonstrated the 
