THE DISCOVERY OF OXYGEN 



then known, even when they themselves have fur- 

 nished the new facts that established another theory, 

 irresistible to minds that were free from the bias of 

 earlier convictions. 



Notwithstanding the known existence of Oxygen, 

 the nature of combustion remained thus misunderstood 

 until ANTOINE LAURENT LAVOISIER (1743-1794) 

 announced his theory thereof. In 1777 he gave to 

 the Academic des Sciences his memoire on "Some 

 substances that are constantly in the state of aeriform 

 fluids at the normal temperature and pressure of the 

 atmosphere." This was the first study of the dis- 

 tinctive nature of gases. This was followed in the 

 same year by his paper on " The constitutive prin- 

 ciple of heat known as Caloric." In the above, as 

 well as in the number of later contributions to the 

 Academic, he expounded his theory of combustion, 

 which taught that "A body can burn only in air 

 holding oxygen (pure air)." By combustion, light and 

 heat which were thought to be substances, but im- 

 ponderable became free, whereby the Oxygen that 

 had been previously with the Caloric was consumed; 

 the air thus losing in weight as much as the burning 

 body gained, and, that the latter, by its union with oxy- 

 gen, formed an acid, or, if a metal, a metallic calx. 

 He also recognized the role that oxygen plays in 

 respiration, whereby the blood in uniting therewith 



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