NITROGEN 



127 



in comparatively large percentages. The pure salt, KNOa, 

 contains nearly 14 per cent of nitrogen, and over 41 per 

 cent of potassium oxide. In commerce, the percentages 

 run 1 or 2 per cent lower than these figures. Potassium 

 nitrate is extensively mined in India; but there is a large 

 demand for it in the arts, especially for the manufacture 



FIG. 47. Loading caliche on railway trucks. 



of gunpowder, consequently the cost is so high that little 

 finds its way into the fertilizer trade. Potash salts from 

 \ the Stassfurt deposits in Germany have been the chief 

 sources of potassium, but other compounds containing 

 nitrogen are much cheaper sources of that element than is 

 potassium nitrate. 



94. Sodium Nitrate, " Chili Saltpeter," " Soda Salt- 

 peter." Deposits of sodium nitrate (NaNOs) are found 



