NITROGENOUS MANUEES 253 



grass and cereals, but gives very good results with 

 turnips, potatoes, fruit, and garden crops. It repro- 

 duces some of the conditions which obtain in farmyard 

 manure, and favours a slow steady growth. 



SULPHATE 01 AMMONIA. 



Ammonia is produced by the decay of nitrogenous 

 organic matter, or more rapidly by the destructive dis- 

 tillation of the same. It is therefore a bye-product in 

 the manufacture of illuminating gas, shale oils, bone 

 char, etc., which are commercially obtained by the de- 

 structive distillation of coal, bituminous shales, bones, 

 horn, etc. When neutralised with sulphuric acid, it yields 

 sulphate of ammonia thus : 



2NH 3 + H 2 S0 4 = (NH 4 ) 2 S0 4 



Ammonia. Sulphuric Sulphate of 

 acid. ammonia. 



Production. Ordinary coal contains from ^ to 1 per 

 cent, of nitrogen. When it is burned in open fires the 

 carbon, hydrogen and sulphur are oxidised, and most 

 of the nitrogen is liberated in the free state. But when 

 it is heated in closed retorts, as in the manufacture of 

 coal gas, oxidation cannot take place, and a large pro- 

 portion of the nitrogen goes off in the form of ammonia. 

 The gases are passed through a cooling apparatus in 

 which the aqueous vapour condenses and retains the 

 ammonia and other soluble substances. The liquid col- 

 lects in a tank placed to receive it and is called the 

 " ammoniacal liquor." A gallon of this product contains 

 about three ounces of ammonia, chiefly in the form of 

 hydrate and carbonate, and smaller quantities of chloride, 

 sulphide, sulphate, thiosulphate and sulphocyanide. 



In order to separate the ammonia from the impurities, 



