204 THE CHEMISTRY OF CREATION. 



It will be readily conjectured that the ulti- 

 mate process of obtaining an accurate statement 

 of the composition of air, that is to say, one 

 of sufficient accuracy to satisfy the chemical 

 philosopher, was yet to be long deferred. The 

 investigation was one of unusual difficulty. The 

 methods of analysis were to the last degree 

 rude and imperfect, and the consequence was 

 that the results were invariably discrepant, and 

 more or less distant from the truth. The prin- 

 ciple upon which they were conducted was in 

 every instance the same, the methods were 

 very dissimilar. The chemical energy of the 

 gas oxygen has already been mentioned, and 

 offers a striking contrast to the inertness 

 of nitrogen. This was taken advantage of by 

 chemists. It was easy to select substances 

 which seized upon oxygen with avidity, while 

 the nitrogen was left wholly uninfluenced by 

 their presence. These substances were of many 

 kinds. To enumerate a few we find employed, 

 sulphuret of potassium, phosphorus, lead turn- 

 ings moistened, spongy platinum, and the gas 

 hydrogen. When the first three of these sub- 

 stances are exposed to air, they immediately begin 

 to oxidate, that is, to absorb its oxygen, leaving 

 all the nitrogen behind. The experiments with 

 spongy platinum and hydrogen were differently 

 conducted to those with the former substances. 



