MANUKES, THEIR KINDS AND USES. 



45 



chemical treatment, by which the potash compounds are 

 more or less completely purified. As prepared for mar- 

 ket, the potash fertilizers contain potassium in the form 

 of either chloride of potassium, or sulphate of potash, 

 and, along with these, other compounds, as shown by the 

 following figures from circulars of the German manu- 

 facturers: 



COMPOSITION OF THE GERMAN POTASH SALTS. 



"All these brands contain other than potash compounds. 

 Of these the sulphate of magnesia may be valuable, since 

 it is useful as plant food, and further, aids in diffusing 

 the potash through the soil and thus bringing it within 

 reach of the roots of plants. The chloride of sodium, or 

 common salt, though not needed for plant food, is useful 

 in rendering other materials available, and hence is often 

 quite valuable as a fertilizer. For certain crops, how- 

 ever, like potatoes, sugar beets, and tobacco, it is apt to be 

 detrimental; probably on account of the chlorine which 

 it contains. The chloride of magnesium may be in- 

 jurious. Nos. 1, 2, 3, and 4, in the table, are low grade 

 articles, furnishing only nine to eighteen per cent, 

 of actual potash. The crude kainit, No. 1, is the ma- 



