387] SCIENTIFIC MANUAL. 101 



The latter is formed naturally in soils, by the disintegration 

 of rocks containing feldspar or mica. The granites of 

 Georgia yield this form by decomposition. 



Carbonate of potash is found in wood ashes, which fur- 

 nishes a cheap, but limited source, of this important and 

 necessary constituent of all fertile soils. The caustic prop- 

 erty of lye is due to potash leached from the ashes. 

 Leached ashes differ from unleached only in the per cent. 

 of potash contained both are valuable as fertilizers. 



Sulphate of potash is derived, principally, from kainit, 

 which is extensively mined near Strassfurt, Prussia. Kainit 

 contains from 23 to 25 per cent, of sulphate of potassa, 

 from 14 to 28 per cent, of magnesia salts, and 30 to 48 

 per cent, of chloride of sodium. Pure sulphate of potassa 

 contains 54 per cent, of potassa, and 46 per cent, of sul- 

 phuric acid. Kainit is the best commercial source of pot- 

 ash, for the reasons that the foreign matters associated with 

 it are, to some extent, valuable as an application to the 

 soil, the sulphuric acid acting as a chemical agent for the 

 reduction of other substances in the soil, the magnesia salts 

 and chloride of sodium serving as plant- food, and the al- 

 kalies being presented in such combinations as not to vola- 

 tilize ammonia from nitrogenous substances, with which 

 the farmer or manufacturer may desire to compound it. 



Chloride of potassium is another important source of pot- 

 ash. It is derived mainly from the mines near Strassfurt, 

 Prussia, where it is found in a vast bed of clay, overlying 

 one of rock salt. When pure, it contains 52.35 per cent, 

 of potassium and 47.65 of chlorine. 



Nitrate of potash, commercially known as nitre or salt- 

 peter, is procured from certain districts in India, and from 

 caves, by simply leaching the earth with water, and evapo- 

 rating the solution thus obtained. It is also made from 

 artificial nitre beds, in many parts of Europe. 



Lime exists in nature in vast quantities. 



1st. As carbonate of lime, which is composed of lime 



