110 AZOTIC GAS. 



water formed was greater, and of carbonic acid 

 smaller, than when charcoal was used. 

 By iron My next process was to mix together nitre 

 and clean iron filings to introduce the mixture 

 into a copper tube and to expose it to a red heat. 

 In this process, the oxygen of the nitre united 

 with the iron filings, while the azote was evolved 

 in the gaseous state. Four experiments made in 

 this way very nearly agreed with each other. 

 I found, that 8*65 grains of nitre gave out four 

 cubic inches of azotic gas, supposing the baro- 

 meter to stand at 30 inches, and the thermome- 

 ter at 60. It will be more convenient to divide 

 these quantities by 4 ; this will give, as a result, 

 1 cubic inch of azotic gas from 2-1625 grains of 

 nitrate of potash. 



Now, since the specific gravity of azotic gas 

 is 0-9722, a cubic inch of it weighs 0-296527 

 grain ; and this is the weight of azote in 2-1625 

 grains of nitre. 



But nitre is anhydrous : the atomic weight of 

 nitric acid is 6*75, and of potash 6 ; conse- 

 quently, nitrate of potash is composed of 



Nitric acid 6- 75 

 Potash 6 



12-75 



And 2-1625 grains of nitre contain 1*144852 

 grain of nitric acid. The preceding experiments 



