4 2 



CHEMICAL FERTILIZERS 



workable conditions. Sea water is concentrated in 

 lagoons by sun heat, so that during the day the water 

 deposits salt, mixed with a little magnesium sulphate. 

 During the night it cools to such an extent that magnesium 

 sulphate crystallizes out, and the density of the liquor falls. 

 Next day, when the water again becomes heated by the sun, 

 the salt deposited does not dissolve, but the layer of magne- 

 sium sulphate is covered by a fresh deposit of mixed salts ; 

 this deposition of alternate layers continues until the mother 

 liquors are sufficiently concentrated. The liquors are removed 

 to large tanks and refrigerated, when Carnallite, a crystalline 

 compound containing potassium and magnesium chlorides, 

 separates out. By treating Carnallite with a little water, 

 most of the magnesium chloride can be dissolved, leaving a 

 product containing about 75 % of potassium chloride. The 

 magnesium compounds are returned to the lagoons, so as 

 to hasten a fresh crop of carnallite crystals. Japan 

 produces 240,000 tons of bittern from the mother liquors of 

 salt pans. This mother liquor contains 68 % of water, and 

 nearly J % of potassium chloride. Of the potassium present, 

 80 % can be recovered as an 80 % potassium chloride. 

 vSicily produces about one-half as much bittern as Japan. 



Table 7 gives the amount of potash in different kinds of 

 salt water. 



TABLE 7. 

 USEFUL SALTS IN SEA WATER. 



Attempts to utilize other minerals containing potassium 

 have not, up to the present, been very satisfactory. Felspar, 

 on heating in a furnace with lime and other substances, can 

 be made to yield a considerable quantity of potassium, but 

 the expense is high, and the by-products are very bulky. 



