NITROGENOUS MANURES 255 



now produced annually in this country alone 1 ; a large part 

 of it is exported, but about 87,000 tons is consumed at 

 home, of which from 80 to 90 per cent, is used in agricul- 

 ture. 



Composition and General Properties. According to the 

 chemical formula given above, sulphate of ammonia con- 

 tains 25'76 per cent, of ammonia, which is equivalent to 

 21 '21 per cent of nitrogen. When pure, it presents the 

 appearance of a colourless, odourless, crystalline salt. 

 The commercial product should contain not less than 

 24*5 per cent, of ammonia, which is equal to 95 per 

 cent, pure sulphate of ammonia. The impurity generally 

 consists of sand, common salt and moisture. A small 

 amount of tarry matter is occasionally present, and 

 imparts a brown or blue colour and characteristic odour, 

 but does not affect the manurial value. Sulphides and 

 sulpho-cyanides are rarely found in samples which have 

 been prepared by distillation. The former can be detected 

 by the odour of sulphuretted hydrogen it resembles that 

 of rotten eggs which is given off when sulphuric or 

 hydrochloric acid is added to the sample. The detection 

 of sulpho-cyanides is equally simple. A few grains of 

 the sulphate of ammonia are dissolved in a wine-glassful 

 of water, and a drop of ferric chloride is added to the 

 solution. If sulpho-cyanide be present a dark red colour 

 is produced, but if absent no change will be observed. 



Adulteration. The high price which sulphate of 

 ammonia commands, offers a certain temptation to adul- 

 terate it. The substances which have been most com- 

 monly employed for this purpose are gypsum, common 

 salt, and sulphate of soda. Two simple tests may be 

 applied as follows: (1) Anything that remains undis- 

 solved when the substance is stirred up with water is 



1 Frank, Chemical Trade Journal, 1908. 



