MANURES. 291 



of ferric chloride solution to a solution of the sulphate, 

 when even a trace of thiocyanate imparts a blood-reel 

 colour to the mixture. 



P reparation. When organic matters containing nitro- 

 gen are heated in the absence of air a proportion of the 

 nitrogen comes off in the form of ammonia gas, and this 

 when combined 'with sulphuric acid yields ammonium 

 sulphate. The great source of ammonium compounds is 

 coal. Ordinary coal contains from 1 tol^% of nitrogen, 

 and in the distillation of this in the preparation of coal 

 gas and coke a certain amount of ammonia is produced 

 and caught in what is known as the "ammoniacal liquor 

 of the gas-works." 



On mixing this strongly alkaline liquid with lime and 

 redistilling it all the ammonia comes off. It is passed 

 into sulphuric acid where it forms sulphate of ammonia 

 \vhich crystallises out on concentration of the solution. 



The salt is also produced in the ] reparation of paraffin 

 oil and paraffin wax from bituminous shale, (a kind of 

 hardened mud containing organic matter), and to a less 

 extent from the waste gases of iron works and from the 

 distillation of bones in the preparation of animal chaicoal 

 for sugar refining and other purposes. 



Details of the world's production of sulphate of ammonia 

 are not available, but in 1905 some 270,000 tons were 

 produced in Great Britain. The price per ton fluctuates 

 between fairly wide margins but the average price during 

 1905 was 1250 P.T. During 1906 'some 700 tons were 

 imported into Egypt for application to the maize and 

 cotton crops and in 1907, 1100 tons. * 



