212 CHEMISTBY. 



water and nitric acid. You see how this is. The oxy- 

 gen unites with the hydrogen of the ammonia to form 

 water, and with its nitrogen to form nitric acid. Then as 

 lime is ready on the spot, the acid at once unites with it, 

 forming calcium nitrate. This is obtained in solution from 

 the mass, and converted into potassium nitrate by treating 

 with potassium carbonate. Insoluble calcium carbonate 

 is precipitated, and potassium nitrate goes into the solu- 

 tion. 



292. Gunpowder. Gunpowder is composed of potassium 

 nitrate, charcoal, and sulphur, each carefully ground, and the 

 three well mixed in proper proportions. The effectiveness 

 of saltpetre as a constituent of gunpowder depends on the 

 fact that it quite readily parts with its oxygen gas, which 

 constitutes nearly one half of the salt. Bloxam thus ex- 

 plains the chemistry of the explosion of gunpowder: "The 

 oxygen of the saltpetre converts the carbon of the charcoal 

 chiefly into carbonic anhydride, part of which assumes the 

 gaseous state, while the remainder combines with the po- 

 tassium of the nitre to form potassium carbonate. The 

 greater part of the sulphur is converted into sulphuric acid, 

 which forms sulphate of potassium. The chief part of the 

 nitrogen contained in the potassium nitrate is evolved in 

 the uncombined state." Several other substances are form- 

 ed in small quantity besides those named, among which are 

 carbonic oxide, marsh gas, potassium sulphide, and sulphu- 

 retted hydrogen. The disagreeable odor of burned gun- 

 powder comes from the formation of sulphuretted hydrogen 

 by the action of the moisture of the air upon the sulphide 

 of potassium. The blackening of the surface of the gun- 

 barrel comes from the formation of sulphide of iron. There 

 is no water of crystallization in nitre. If there were any, 

 it would unfit it for being an ingredient in gunpowder ; for 

 this water, being released by the heat, would tend to put 



