PRINCIPLES OF MANURING 119 



Sulphate of ammonia is a substance of 

 which, when pure, every 132 Ib. contain 

 28 Ib. nitrogen, 8 Ib. hydrogen, 32 Ib. 

 sulphur, and 64 Ib. oxygen. But, like 

 nitrate of soda, this substance is not used 

 for manurial purposes in a chemically 

 pure condition, the degree of purity being 

 usually 97 per cent. By calculation 

 we find that if 132 Ib. of pure sulphate of 

 ammonia contain 28 Ib. of nitrogen, 97 Ib. 

 will contain 20 - 6 Ib. Seeing that 97 per 

 cent, of purity is the basis upon which we 

 usually purchase this manure, it follows that 

 the percentage of nitrogen in ordinary com- 

 mercial sulphate of ammonia is 20'6. From 

 this it can be calculated that a ton of com- 

 mercial sulphate of ammonia contains rather 

 over 461 Ib. of nitrogen, and at present the 

 price is about 12 per ton. On this basis it 

 will be found that the price per pound of 

 nitrogen in sulphate of ammonia is 6 -3 pence, 

 as contrasted with 6'9 pence in the case of 

 the nitrate of soda. At the prices we have 

 assumed, therefore, sulphate of ammonia is 

 better value than nitrate of soda to the 

 extent of rather over d. per Ib. ; and if, in 

 other respects, it is a matter of indifference 

 which substance we employ, we should un- 

 hesitatingly give the preference to the former. 



