II.] 



SULnrATE OF AMMOXIA 



59 



is redistilled into sulphuric acid and sulphate of 

 ammonia is crystallised out; the resulting commercial 

 salt contains about 205 per cent, of nitrogen. Not only 

 gas works, but blast furnaces, coke ovens, shale oil 

 works, etc., are now arranged to recover this valuable 

 product of the coal, and the accompanying table shows 

 the current output from each of these sources : — 



Table XIII.— Production of Siuhate of Ammonia in thh 

 United Kingdom. 



In the early days of the industry hydrochloric acid 

 was sometimes employed, in which case ammonium 

 chloride (muriate of ammonia) was obtained, but the 

 only salt now prepared as a manure is the sulphate. 



Sulphate of ammonia, when pure, is a white crystal- 

 line salt freely soluble in water ; the commercial article 

 varies somewhat in colour, being generally grey or 

 yellow from a trace of tarry matter ; in some cases it is 

 distinctly blue, owing to the presence of a little ferro- 

 cyanide, derived from the cyanides always present in 

 coal-gas. The pure salt contains 21-2 per cent, of 

 nitrogen, and as the commercial article is generally of 



