LAVOISIER 5 



the increased weight of iron after being heated in air was 

 due to its absorption of something in the air : " II est 

 tres possible que cette augmentation de poids soit venue 

 de la matiere r^pandue dans 1' atmosphere." (See Voltaire's 

 paper in Recueil des Pieces qui out remporte les Prix 

 de r Academic royale des Sciences, Paris, 1752, tome iv., 

 p. 171.) 



Although Priestley first isolated " dephlogisticated air" 

 or oxygen, it was left for the genius of Lavoisier to first 

 interpret the phenomenon of combustion ; and in 1778 (the 

 year that witnessed the deaths of Voltaire and Rousseau 

 within thirty -three days of each other) he established the 

 fact that oxygen was the universal oxidizing principle. 



During 1775 and subsequent years Lavoisier expounded 

 his views on the nature of respiration, fermentation, and 

 combustion ; and we have to this day excellent sepia 

 drawings by Madame Lavoisier of her husband's experi- 

 ments on respired air. 



In 1783 the composition of water was discovered by 

 Cavendish, and confirmed the same year by Lavoisier and 

 Laplace. Lavoisier was then able to explain the reactions 

 which take place when metals dissolve in acids ; and when 

 metals burn to form calces, that oxygen is instrumental 

 in the combustion. From the work of Cavendish, he first 

 clearly stated the compound nature of water, and deter- 

 mined accurately its volumetric composition (Kopp). 

 " Although Cavendish was the first to show that water is 



