3 2 



which becomes damp when mixed with other manures, and 

 spoils the condition of the mixture. 



An important exception must be made in the case of 

 manures containing lime or carbonate of lime. Any such 

 manure as, for instance, Thomas phosphate or basic slag 

 if mixed with sulphate of ammonia will cause a considerable 

 amount of ammonia to be given off into the air, especially 

 during the mixing and sowing. Carbonate of lime is less 

 active in this respect, but may cause an appreciable loss 

 particularly if the mixture is damp. It may be added that 

 nitrate of soda suffers no loss of nitrogen in this way by con- 

 tact with lime. 



COMPOSITION OF SULPHATE OF AMMONIA. 



In the pure state sulphate of ammonia has the chemical 

 formula 2NH 4 ,SO 4 , implying that two atoms of nitrogen, 

 eight of hydrogen, one of sulphur, and four of oxygen are 

 united in it. Expressed by weight, its composition is : 



Nitrogen 21-21 per cent. 



Hydrogen 6-06 



Sulphur 24-24 



Oxygen 48-48 



As it is usually sold, sulphate of ammonia of good quality 

 is of from 95 to 97 per cent, purity that is, 95 to 97 per 

 cent, is actual sulphate of ammonia; the remainder con- 

 sisting chiefly of moisture, with any earthy or other im- 

 purity that may have become accidentally mixed with it. 

 Such manure will contain from 20*15 to 20^57 per cent, of 

 nitrogen. 



For trade purposes, nitrogenous manures are usually 

 described as containing , a certain percentage of ammonia, 

 though in many cases their nitrogen is not in that form. 

 This is merely a conventional way of expressing the amount 

 of nitrogen present. It has been said that there are four- 

 teen parts of nitrogen by weight in ammonia and three of 

 hydrogen. Therefore fourteen- seventeenths of the weight 

 of ammonia consists of nitrogen. Similarly, if a manure 

 contains 14 per cent, of nitrogen, it will be described as 

 having 17 per cent, of ammonia. 



In the case of sulphate of ammonia, therefore, containing 

 2O'5 per cent, of nitrogen, the amount of ammonia equiva- 

 lent to this will be 20-5 X ^, or almost exactly 24-9 per 



H 



cent. In deciding upon the relative economy of using one 

 nitrogenous manure or another, and in comparing market 

 quotations, it is important to bear in mind the distinction 

 between nitrogen and ammonia, and the numerical relation- 

 ship (14 : 17) which exists between them. 



