BEGINNINGS OF MODERN CHEMISTRY 



such men as Dr. John Hunter expressed their belief in 

 its efficacy in certain conditions, as we shall see, but its 

 value in medicine was not fully appreciated until sev- 

 eral generations later. 



Several years after discovering oxygen Priestley thus 

 summarized its properties: " It is this ingredient in the 

 atmospheric air that enables it to support combustion 

 and animal life. By means of it most intense heat 

 may be produced, and in the purest of it animals will 

 live nearly five times as long as in an equal quantity of 

 atmospheric air. In respiration, part of this air, pass- 

 ing the membranes of the lungs, unites with the blood 

 and imparts to it its florid color, while the remainder, 

 uniting with phlogiston exhaled from venous blood, 

 forms mixed air. It is dephlogisticated air combined 

 with water that enables fishes to live in it." 5 



KARL WILHELM SCHEELE 



The discovery of oxygen was the last but most im- 

 portant blow to the tottering phlogiston theory, though 

 Priestley himself would not admit it. But before con- 

 sidering the final steps in the overthrow of Stahl's 

 famous theory and the establishment of modern chem- 

 istry, we must review the work of another great chem- 

 ist, Karl Wilhelm Scheele (1742-1786), of Sweden, who 

 discovered oxygen quite independently, although later 

 than Priestley. In the matter of brilliant discoveries 

 in a brief space of time Scheele probably eclipsed all his 

 great contemporaries. He had a veritable genius for 

 interpreting chemical reactions and discovering new 

 substances, in this respect rivalling Priestley himself. 

 Unlike Priestley, however, he planned all his experi- 



TOt. IV. J 23 



