536 AGRICULTURAL ANALYSIS 



In like manner the insoluble portion was examined and by in- 

 cineration yielded : 



Per cent. 



Organic matter 95-94 



Ash 4.06 



Or, for 100 parts organic matter 4.21 of ash. 



The organic matter had the following composition: 



Carbon 49-5 1 



Hydrogen 6.31 



Nitrogen 2.21 



Oxygen and undetermined 4* -97 



The ash was composed of : 



Potash o. 13 



Lime 0.62 



Silica 2.31 



Alumina, phosphoric acid, etc 0.41 



Carbonic acid, different compounds and loss 0.74 



Total 4.21 



From the above it is seen that the soluble part contains the 

 greater quantity of the mineral compounds, not only as was to 

 be expected of potash, but also of lime and silica. Nevertheless, 

 there exists in the plant a notable quantity of potash entangled 

 in some compound insoluble in water, amounting to about two- 

 tenths of the total potash per cent. 



456. Forms in which Potash is Found in Fertilizers. The chief 

 natural sources of potash used in fertilizer fabrication are : First, 

 the natural mineral deposits, such as Stassfurt salts ; second, the 

 ash derived from burning terrestrial plants of all kinds; third, 

 organic compounds, such as desiccated mineral matters, tobacco 

 waste, cottonseed hulls, etc. 



All these forms of potash may be found in mixed fertilizers. 

 While the final methods of analyses are the same in all cases the 

 preliminary treatment is very different, being adapted to the 

 nature of the sample. For analytical purposes, it is highly im- 

 portant that the potash be brought into a soluble mineral form, 

 and that any organic matters which the sample contains be 

 destroyed. If the sample be already of a mineral nature, it 



