70 HATCH EXPERIMENT STATION. [Jan. 



of the phosphoric acid is based, 'as a rule, on the amount of 

 available phosphoric acid present. ^I;inufoeturci*s of phos- 

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

 by chemic:vl analysis, will show the largest amount of avail- 

 able phosphoric acid : this result is obtained by fiising the 

 slag at al>out 900^ C. with sufficient quartz sand to change 

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

 tliis process (G. Hoyermauu) has published jis an illustration 

 the following results : — 



Analyses of Thomas Phos}^aiic Slag {Per Cent.). 



[L, »nalTsis of Thomas phosphadc sl.^5 Ivfore smelting -with quartz sand; TT., 

 analysis of til? same marerial after fusing ■with qnarta sand.] 



OONSTITUKSTS. I. II. 



CtJeiim oxide (free linae'^, ' 11.00 .70 



Silkicadd, 2toS 12.00 



ATulaHe pbospboric acid ^percentage if wlivrle" , . . . . 5<.(X* S4.00 



The general introduction of Hoyermanu's process has 

 chanired the character of the phosphatic slag of earlier jears 

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

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

 jmy beneficial effect 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. Xo representative sample 

 of this material has j'et come to the writers notice. 



