Another valuable source of phosphoric acid is in Boneblack. 

 This substance is simply bone charcoal ; it is used by sugar re- 

 finers, the raw sugars being filtered through it. In this process 

 the impurities of the sugar are held by the boneblack and from 

 the syrup the granulated sugar is crystalized. After a time the 

 boneblack loses its power of removing the impurities, it is then 

 sold to fertilizer manufacturers, for it contains the phosphate of 

 lime originally in the bone. 



Crude boneblack contains about thirty-four per cent of in- 

 soluble phosphoric acid. 



At the present time there is a comparatively new source of 

 phosphoric acid is the so-called Thomas-Gilchrist Slag. This 

 comes from the manufacture of iron or steel from certain ores of 

 iron, which contain phosphoric acid. The slag has about twen- 

 ty per cent of phosphoric acid in a form not soluble in water. 



POTASH. 



Until 1868 the chief source of potash was wood ashes. It 

 is true that nitrate of potash, or saltpetre, has been used from a 

 very early time, records daring back to 1625, but it was more 

 for the nitrogen which this substance contained, then for the 

 potash ; hence we may regard the discovery and use of the 

 " German Potash Salts," as the first rival of jashes. Unleached 

 wood ashes vary very much in their composition, containing 

 from two and five-tenths to eight and one-half per cent of actual 

 potash. In "Canada" ashes* the average is not far from six 

 per cent, of actual potash (K2O). While leached ashes may 

 contain anywhere from one-half to two*and one-half per cent, ac- 

 cording to the thoroughness of leaching. 



GERMAN POTASH SALTS. 



About 1850 an effort was made to open a salt mine at 

 Stassfurt in Saxony. Salt was reached in 1857 at a depth of 

 over one thousand feet. In sinking the shaft beds of potash 

 and magnesia salts were passed through ; in 1861 a factory was 

 established to purify these salts and put them in commercial 

 form. The first of these crude chemicals were brought to the 

 United States in 1868. There are several forms of these salts, 

 the muriate, sulphate, also what is called kainit, krugit, etc. 



♦Massachusetts Experiment Station Report 1887, average of seventy-one 

 analyses. 



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