264: SUPERPHOSPHATE OF LIME. 



itate the lime from the phosphoric acid, and that alone with 

 soluble alkaline phosphates remains. By potash, soda, or 

 ammonia, all the phosphoric acid may be converted into 

 soluble, neutral phosphates, as will be presently shown. 



Again, a portion of oil of vitriol, amounting to 3J per cent. 

 (306), is found in the crude mass termed superphosphate. 

 It has its use. It prevents earthy bases in the soil, or com- 

 post heap, from uniting with the phosphoric acid. It com- 

 bines with any free ammonia in the compost heap, to which 

 the superphosphate may have been added, and forms mere 

 sulphate of ammonia. If the superphosphate is mixed with 

 guano, the same effect follows. The abundance of sulphate 

 of lime in a very finely-divided state in the crude superphos- 

 phate contributes to the formation of sulphate of ammonia 

 in compost, or guano, when all the oil of vitriol is exhausted, 

 a little soluble sulphate of ammonia being likewise formed. 

 Under every view, the tendency of the phosphoric acid is to 

 remain free. But this free acid is not what the plant de- 

 mands. Plants want soluble phosphoric acid salts, that is, 

 alkaline phosphates, and therefore the farmer should see that 

 all his phosphoric acid is converted to that state. 



How may this be effected 1 In several : two or three of 

 these may be mentioned, which the author has practically 

 proved to form as effectual a " superphosphate" as any article 

 bearing that name in the market, whatever its prefix or suffix 

 may be. 



1. If a forcing, early effect is desired, united to the lasting 

 operation of common bone meal, or supherphosphate of lime, 

 mix as follows ; 



50 lbs. of crude superphosphate made as described (307), in dry powder. 

 25 lbs. of soda ash of commerce, of about 80 per cent, strength. 

 25 lbs. of Peruvian guano. 



Mix well together the superphosphate and soda ash, then 



