8 Preparation of Substances 



by acid in the soil, the steps in the process 

 being first, the production of ammonium 

 carbonate, (NH4)2C03, from the amino 

 groups, — NH2, in the plant; second, the 

 oxidation of ammonia to nitrous acid by 

 bacteria; third, the conversion of the raw 

 rock to dissolvd rock by the action of the 

 nitrous acid which may be represented by 

 the equation, 



Ca3P208 + 4HNO2 + H2O = CaH4P208 • H2O 



+ 2Ca(N02)2; 



and fourth, the oxidation of the calcium 

 nitrite, Ca(N02)2, to calcium nitrate, 

 Ca(N03)2, by the action of bacteria. Both 

 the acid phosphate and the calcium nitrate 

 resulting from the action are available to the 

 plants for food. Naturally the plants richest 

 in amino groups, such as clovers and alfalfa, 

 are most desirable to plow under with the 

 raw rock. This action of the dissolving of 

 raw rock by acid in the soil has been demon- 

 strated by Professor Hopkins in the labora- 

 tory, but others deny that it actually takes 

 place in the soil. 



As a general conclusion it may be said 

 that all the phosphorus of acid phosphate 

 is immediately available to plants while only 

 a small amount of the phosphorus in the 

 raw rock is available during one growing 



