231, 232] Analysis of Superphosphate of Lime 143 



its equivalent of Ca 3 (P0 4 ) 2 (multiply percentage of P 2 5 by 155 

 and divide by 71), and the result entered thus : 



231. A second method, which is rather more scientific, 

 is as follows : Moisture, organic matter, and soluble phosphoric 

 acid are estimated as before. 



Total phosphate and lime. Two grams are weighed out and 

 treated exactly as though a sample of bones, CaC0 3 , sand, and 

 Mg 2 P 2 7 were being weighed. 



232. Calculation. — The soluble phosphate is calculated 

 as before, together with its equivalent in tribasic phosphate 

 of lime. The total P 2 5 is calculated into Ca 3 P 2 8 . From 

 this is subtracted the Ca 3 P 2 8 which has been calculated as 

 equivalent to the soluble phosphoric acid. The remainder is 

 the insoluble phosphate of lime. 



From the weight of CaC0 3 the percentage of CaO is calcu- 

 lated (multiply by -56). From this is subtracted the amount 

 of CaO contained in the soluble CaP 2 6 and the insoluble 

 Ca 3 P 2 8 , and the remainder is calculated out as CaS0 4 . 



These calculations from the CaC0 3 precipitate may be 

 simply and rapidly done as follows : 



Subtract the soluble from the total P 2 5 ; result m insoluble 

 P 2 6 . 



