Phosphates 



Cambridgeshire, also in Bucks, Beds., Dorset, the 

 Isle of Wight, etc. 



Lawes used them in 1845 in making superphos- 

 phates to replace bones which were too scarce and 

 too dear. Phosphate is present in the tricalcic form 

 [Ca3(P04)2]. Their least value of phosphoric acid 

 [P2O5] is 20 to 23 per cent., with some considerable 

 exceptions, however, as they sometimes contain from 

 40 to 47 per cent, tricalcic phosphate. But besides 

 phosphate of lime and other phosphates they also 

 contain sulphates, carbonates, fluoride, etc., which 

 make the manufacture of superphosphate difficult. 

 That is why they have been replaced by other 

 phosphates without these inconveniences. The Co- 

 proliths are often ground very finely, and used as a 

 tribasic phosphate manure. They are not always 

 suitable for this purpose, since in alkaline or simply 

 neutral soils, they will have very little effect. But 

 in acid soils they will be one of the best insoluble 

 phosphates to use, costing less than bones, and giving 

 almost as good value. 



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