Nov.. 191:^.] 



Wheat and its Cultivation. 



69: 



From the mineral 

 phosphates and 



l)oii('s, such mannfac- 

 tiired phosphatic fer- 

 tilizers as super- 

 phosphate, dissolved 

 bones, concentrated 

 superphosphate. are 

 obtained. 



, Phosphates of Lime. 

 — The calcium com- 

 pounds are by far the 

 most important of the 

 compounds of phos- 

 phoric acid, and a 

 knowledge of these is 

 of practical impor- 

 tance to the farmer. 



Phosphoric acid 

 (P.2O., WH.A)) forms 

 with lime three dis- 

 tinct compounds, 

 namely, tricalcic, di- 

 calcic, and monocalcic 

 phosphate. 



In these three com- 

 pounds, one part ot 

 phosphoric acid com- 

 bines with three, two, 

 and one part of lime 

 respectively. The de- 

 gree of solubility 

 of these compounds 

 varies considerably. 

 Thus, the tricalcic 

 form (3Ca, < )!%<),) 

 containing one part 

 of phosphoric acid 

 combined with three 

 parts of lime, is in- 

 soluble in water, in 

 weak organic acids, 

 and is oidy soluble in 

 mineral acfds. such as 

 sulphuric acid. It is 

 the form found in 

 bones and in rock 

 phosphate and guano. 

 It corresponds to the 

 insoluble phosphate 

 on the manure 

 guarantee tags. 



