162 CHEMICAL MANUEES. 



of alumina to form an aluminate of ammonia. A product is thus 

 obtained which remains as dry as ordinary phosphate. The 

 chemical transformation then becomes : — 



AIPO4 + 3AmHS0^ = AlAm(SOj- + AmHSO^,AmH,PO^ 



If the Eedonda phosphate contains, for example, 40 per cent 

 P.,Or,, one calculates thus : — 



100 phosphate 4OP0O.3 



112 sulphate of ammonia ...... 'i4N 



130 sulphuric acid of 50" B 8IH0SO4 



342 



We thus get a manure containing in round figures : — 



Pei' cent. 



Nitrogen 8-0 ^ 



P0O5 total 13-0 



P2O5 soluble in water ...... 11"0 



In many cases it would be advisable to replace a portion of the 

 nitrogen by potash. This substitution is easily effected. It suffices 

 to replace t le sulphate of ammonia to form alum by sulphate of 

 potash : — 



AlPp + 2AmHS0, + KHSO, = A1K(S0J2 

 + AmHSO^,AmH,PO^ 



The addition of potash in quantity greater than to combine with the 

 alum complicates the work. It is clear, moreover, that one can 

 likewise combine with this process the production of aluminate 

 of ammonia ; the expense adherent to washing, evaporation, and 

 crystallization appears, to be largely covered by the sale of the sul- 

 phate of alumina as a current article of commerce, whilst the 

 richness of the manure would be increased at will. 



By working as described, it is easy to utilize Eedonda phosphate 

 up to 90 per cent. As already mentioned, the sulpho-phosphate of 

 potassium does not combine the conditions required in a concen- 

 trated potassic manure. Its sulphuric acid, amounting to almost 

 30 per cent, must be removed. Lime provides the easiest means. 

 It has been proposed to combine monocalcic phosphate with 

 sulphate of potash, but the process is not applicable because the 

 gypsum is precipitated in the form of very attenuated crystals, 

 which render filtration impossible after evaporation. But if lime 

 in an insoluble form be used, i.e. as carbonate, and if it be made to 



1 If 312 of tinished manure gives 21X, 100 only gives 7, not 8. — Tu. 



