70 HATCH EXPERIMENT STATION. [Jan. 



of the })hosphoric acid is based, as a rule, on the amount of 

 available phosphoric acid present. Manufacturers of phos- 

 phatic slag have aimed at the production of a material which, 

 by chemical analysis, will show the largest amount of avail- 

 able phosphoric acid ; this result is obtained by fusing the 

 slag at about 900° C. with sufficient quartz sand to change 

 the free lime present into silicate of lime. The inventor of 

 this process (G. Hoyermann) has published as an illustration 

 the following results : — 



Analyses of Tliomas Phosphatic Slag (^Per Cent.). 



[I., analysis of Thomas phosphatic slag liefore smelting with quartz sand; II., 

 analysis of the same material after fusing with quartz sand.] 



CONSTITUENTS. 



I. 



It. 



Calcium oxide (free lime) , 



Silicic acid 



Available jihoBphoric acid (percentage of whole), . 



11.00 

 2 to 3 

 58.00 



.70 

 12.00 

 84.00 



The general introduction of Hoyermann's process has 

 changed the character of the phosphatic slag of earlier years 

 materially. The phosphatic slag of to-day contains, in ex- 

 ceptional cases only, some free lime, not sufficient to charge 

 any beneficial efi'ect of the phosphatic slag on the crop raised 

 to free lime present. 



An imitation of phosphatic slag is reported as having been 

 introduced in Sweden. It is obtained by fusing apatite with 

 soda ash at from 700° to 800° C. No representative sample 

 of this material has yet come to the writer's notice. 



