LESSONS IN CHEMISTHY. 



ture of gunpowder, puts potassium in the front rank of useful 

 metals. 



Gunpowder is an intimate mixture of potassium nitrate, sul- 

 phur and powdered charcoal. The nitrate furnishes oxygen in 

 great abundance, charcoal, carbon in available form, and the 

 sulphur ignites at a low temperature, altogether tending to 

 rapid and intense combustion. The nitrate for the manufacture 

 of gunpowder should be free from the chlorides of potassium and 

 sodium, should be free from coloring matter and should show 

 neither acid nor alkaline reaction. The charcoal for gunpowder is 

 best made of some light wood, as alder or willow, as charcoal 

 from these woods is lighter and more easily combustible. The 

 wood is burned in a retort at a temperature of about 1,000 F. 

 which yields a charcoal of the most desirable density. The char- 

 coal is allowed to cool slowly, and is then exposed to the air for 

 several days, so that it may absorb moisture ; for if ground be- 

 fore it is liable to spontaneous combustion. It is then ground 

 and sifted to free it from dust. Distilled sulphur is used, as it is 

 soluble and free from sulphurous and sulphuric vapors. The pro- 

 portions of these ingredients varies among manufacturers. Eng- 

 lish government powder contains 75 per cent, of saltpeter, 15 

 per cent, charcoal and 10 per cent, sulphur. These substances 

 are first thoroughly mixed, and the mixture, in charges of about 

 50 pounds each, is subjected to the action of the incorporating 

 mill, which is something like the dry pan used in preparing clay 

 for brick making, consisting of heavy iron rollers with scrapers 

 and plows so as to keep the mass well mixed while it is being 

 pressed by the rollers. This process continues about three hours 

 for slow-burning cannon powder, and about five hours for rifle 

 powder. The mass is sprinkled with water during the time, so 

 that at the close of the process the grayish mass of mill cake 

 contains from 2 to 3 per cent, of water. The mill cake is broken 

 up and packed in layers about half an inch thick between copper 

 plates and subjected to great pressure under the hydraulic press. 

 This not only makes the powder compact, but it seems to have 

 less capacity for absorbing moisture. But this mass will not 



