[ 550 ] 



much as 45 per cent, of soluble phosphates calculated as 

 CasP 2 O 8 . The soluble phosphate of the manufacturer is not 

 CaH 4 P 2 O8, but is expressed in the terms of Ca 3 P 2 O8 which have 

 been rendered soluble. 20 per cent, of soluble phosphates 

 means 20 per cent, of CasPgOs made soluble which is actually 

 15 per cent, of monocalcic phosphate (CaH^PsOs). Super is 

 sometimes said to contain so many per cent, of biphosphate 

 (CaPaOe), in which case the soluble phosphate instead of 

 being expressed in the terms of monocalcic or tricalcic phos- 

 phate, is expressed in terms of the so called biphosphate which 

 is properly speaking calcium metaphosphate, obtained by 

 drying monocalcic phosphate. 



Now the molecular weight of P2O 5 , CaH 4 P2O 8 , CaPaOe, and 

 are respectively 142, 234, 198 and 310. Taking 

 s as unit, CasP2O8 and CaP 2 O6 bear the proportion 

 of 1*33 : '85. Super is also sold at so much " per unit/- 

 unit meaning i per cent, of soluble phosphate per ton. 

 The insoluble phosphates are not valued in purchasing 

 mineral super after analysis, but in purchasing bone-super 

 the insoluble phosphates are also valued. 



899. The following table gives the percentage composi- 

 tions of the principal varieties of super : 



Bone super. Super from Mineral -Concent- 



bone-ash. super, rated super.' 1 



Moisture ... 8 % 6 % 15 % 13 % 



Organic matters 

 and combined 

 water 

 CaH 4 P 2 O 8 



Ca 3 P 2 O 8 ... 



CaSO 4 



Alkaline salts, &c. 



SiO 2 ... 



N(-NH 3 ) ... 



