102 AZOTIC GAS. 



anhydrous ; a moderate heat drives off the water 

 of crystallization with great facility ; and we may 

 afterwards fuse it, to be absolutely certain that 

 all traces of water are removed. 



When this salt is anhydrous, it is composed of 



1 atom sulphuric acid = 5 

 1 atom soda = 4 



9 



so that nine grains of it contain exactly five 

 grains of sulphuric acid. 



The nature and constitution of these two salts 

 being understood, we are prepared to investigate 

 the weight of an integrant particle of nitric 

 acid. 



I took two small glass vessels, containing each 

 a little distilled water ; in the one, I dissolved 

 20*75 grains of pure nitrate of lead, and in the 

 other, 9 grains of anhydrous sulphate of soda. 

 These two solutions being mixed together, a 

 double decomposition took place ; the sulphuric 

 acid and oxide of lead uniting together, and 

 forming an insoluble sulphate of lead, which fell 

 rapidly to the bottom, while the nitric acid and 

 soda remained in solution in the colourless li- 

 quid. As soon as the sulphate of lead had left 

 the liquid quite clear and transparent, a few 

 drops of it were put into two different watch 

 glasses y into one of these, I let fall a little of 



