Nitrogenous Manures 



hot shovel. If any residue is left the sulphate has 

 been adulterated. 



Sulphate of ammonia is principally obtained 

 in the making of coal gas. By the distillation 

 of coal, nitrogen is converted into ammonia, which 

 is retained m the water used in the first purifi- 

 cation of the gas. This water is mixed with 

 sulphuric acid and sulphate is obtained. It is 

 largely produced and used in England, Lawes 

 and Gilbert being quoted amongst the best autho- 

 rities on its use. For a long time it was believed 

 that the ammonia ought to be nitrified to make 

 it assimilable for plants, but it has been proved 

 by Muntz and Breal that cereals can assimilate it 

 in a natural state. The process is generally as 

 follows. When the conditions for nitrification are 

 fulfilled the sulphate of ammonia reacts on the 

 carbonate of lime and obtams from it carbonate 

 of ammonia and sulphate of lime — which latter 

 is lost in the drains. So that the prompt and con- 

 stant use of lime after sulphate of ammonia is 

 necessary. The carbonate of ammonia is then de- 

 composed by the zoolites of the clay or the calcaire 

 of the humates which fix the ammonia and free the 

 sodium or calcium. Afterwards the microbe of 

 nitrification turns the ammonia first into nitrite and 

 then into nitrate of lime by oxidisation. For the 

 oxidisation to act easily the soil must be well aerated, 

 and also have some degree of warmth. It cannot 

 take place in a cold soil. So that during the winter 

 neither nitrification nor loss of nitrogen by means of 

 sulphate of ammonia takes place. 



Sulphate of ammonia must therefore be used 



40 



