136 ELEMENTS OF AGRICULTURE 



house, and is made up of the refuse parts of the 

 slaughtered animals. It contains from 10 to 12 per 

 cent of nitrogen. 



7. Fish scrap is a by-product from the fish canneries, 

 where large quantities of fish are preserved in cans for 

 the market. The refuse parts of the fish are dried and 

 sold as a fertilizer. It contains from 7 to 9 per cent 

 of nitrogen. 



129. Potash. — Until about forty years ago all the 

 potash of fertilizers was supplied by wood ashes, stable 

 manure, and waste products, such as rotting straw or 

 tobacco stems. About the year 1860 there were found 

 in Germany, near the town of Stassfurt, great deposits 

 of potash salts, which were probably left there by the 

 evaporation of some inland sea or lake. Great quanti- 

 ties of these potash salts are now mined and sold, the 

 Stassfurt mines supplying potash to the entire world. 

 The potash salts as found. in the mines are mixed with 

 various other compounds, such as common salt, mag- 

 nesium chlorides, epsom calts, etc. From this mixture 

 pure potash salts are prepared. 



1. Kainit is the crude salt as it comes from the mine 

 and contains a number of different compounds. Most 

 of the potash in kainit is in the form of a sulphate; 

 that is, it is combined with sulphur and oxygen. It 

 contains only about 12 per cent of potash. 



2. Sylvinit is another of the crude salts, and most 

 of the potash it contains is in the form of a chloride. 

 Sylvinit contains from 15 to 20 per cent of potash. 



3. Muriate of potash, which is manufactured from 

 the crude salts, such as kainit, is a compound of potas- 



