134 PHOSPHATIC MANURES 



in a platinum basin and ignited carefully until free 

 from ammonium salts. The potassium is then esti- 

 mated in the residual alkaline chlorides by means 

 of platinic chloride (79, p. 99). The sodium, if required, 

 may be obtained by difference from the weight of 

 mixed chlorides. 



120. Sulphate. 



The sulphuric acid is estimated in the original 

 solution as BaS04, ^Y precipitation with barium 

 chloride. 



121. Statement of Results. 



Whatever the form of phosphate estimated in 

 agricultural analysis, the result is always stated in 

 terms of the tricalcium phosphate, Ca3(P04)2, or as 

 phosphoric anhydride, P2O5. One part of the latter 

 equals 2- 18 of the former. The results of a complete 

 analysis of superphosphate should be stated as 

 follows : — 



Per cent. 



Moisture . . . . .20-53 



Combined Water and Organic Matter con- 

 taining nitrogen =0-32 ammonia . 1476 

 Soluble Phosphate as Ca3(P04)2) containing 



11-99 per cent. PgOg . . . 26-14 



Insoluble Phosphate 

 Reverted Phosphate 

 Calcium Sulphate^ CaSO^ 

 Potash and Soda, KgO + NagO 

 Silicious Matter, etc. . 



1.81 



37.28 

 1-48 



4.44 



Basic Slag. 



Basic slag is a by-product in the manufacture of steel from 

 pig-iron which has been prepared from phosphorus-rich iron 

 ores. It depends for its activity chiefly on its fine state of sub- 



