ft - . 



TV 1 



TY 



SUPERPHOSPHATES. 157 



Since Ca 3 P. 2 K corresponds to CaH 4 P. 2 O H 



120 + 62 + 128 40 + 4 + 62 + 128 



310 234 



the amount of real calcium tetrahydrogen phosphate cor- 

 responding to "24% soluble" would be 24xff = 18'l; but 

 even this is not what is meant, for by " monocalcium phos- 

 phate" in the trade the substance CaP. 2 O (i (really calcium 

 meta-phosphate, which is not present in manures) is under- 

 stood ; so that as this contains the same amount of P. 2 O 5 as 

 Ca 8 P. 2 8 the connection becomes 



CaP. 2 O, ; corresponds to Ca 3 P. 2 O H 

 40 + 62 + 96 120 + 62 + 128 



198 310 



Consequently, in the trade, the quantity of monocalcium phos- 

 phate equivalent to "24% soluble phosphates" or to "24% 

 bone phosphate rendered soluble," as it is sometimes more 

 explicitly described, is given by 



By the term "insoluble phosphates" in the above analyses 

 is meant the amount of tricalcium phosphate present as such, 

 together with that equivalent to the dicalcium phosphate or 

 "reverted" phosphate. The latter is much more valuable 

 than the former and in recent analyses the quantities of each 

 present are given (see Chapter VIII.). 



Eeference may here be made to a recently patented manure 

 to which the contradictory name of basic superphosphate -k&$ 

 been given. This is a product obtained by adding 15 parts of 

 slaked lime to 85 parts of good superphosphate, thoroughly 

 mixing the two, and allowing them to stand at least 24 hours. 

 A dry, bulky powder is thus produced, which, it is claimed, 

 has many advantages over basic slag." Some of the analyses 

 advanced in support of the claim were, in the present writer's 

 opinion, far from conclusive. To quote one as an example: 

 A comparison was made between the new manure and basic 



* Hughes, Jour. Soc. Chem. Iml. 1901, 325. 



