XITEOGENOUS MANUEES. 225 



Formerly, ammoniacal salts were made solely from matters of 

 animal origin. They were charj;ed into retorts which were heated 

 to incandescence, the vapours given off being condensed. The car- 

 bonate of ammonia thus obtained was collected and purified or 

 combined with acids to form different salts. The process is still 

 applied in the manufacture of small quantities of sal-ammoniac, but 

 solely as a bye-product in the manufacture of animal charcoal. The 

 calcination of the bones is done after two different methods. The 

 one, the older, consists in charging the raw material in vessels 

 placed in a furnace in stages so that one serves as a lid to the other 

 underneath. The vapours given off during combustion, the details 

 of which need not be dwelt upon, escape outwards by the chimney. 

 The other method consists in calcining the bones in a cast-iron re- 

 tort analogous to that used in distilling coal. The gases which are 

 given off are collected and condensed. The products of the con- 

 densation contain among other useful substances ammonia, which 

 can be extracted by distillation and converted into sulphate of 

 ammonia. But, as already observed, bone black is no longer used in 

 sugar factories. With the disappearance of bone black, the bye- 

 products, especially ammonia, also disappeared. The most important 

 source of ammonia is at present coal, the percentage of nitrogen in 

 which varies from 0"O to 1-6 per cent. The extraction of ammonia 

 will therefore be studied in the following order : (1) In the manu- 

 facture of gas ; (2) in the manufacture of coke ; (3) in the blast 

 furnaces, and (4) in the gasogene ovens (Mond's process, Bourgeois 

 and Lencauchez' process). 



Manufacture of Sulphate of Ammonia by Distillation of Gas 

 Liquor. — When coal is distilled, the nitrogen which it contains 

 passes partly into the tar as complex products (aniline and its 

 analogues) and partially in the form of ammonia in the illuminating 

 gas. The ammonia is eliminated from the latter by washing with 

 water. According to Eoscoe, only 14*5 per cent of its nitrogen is 

 obtained from coal as NH3, 35*26 per cent is lost as free N, 

 w^hilst the coke retains 48 to 68 per cent. This low yield of 

 ammonia is due to the facility with which this gas is decomposed 

 (at a temperature of 500° C, Eamsay and Young). This loss may 

 be avoided by preventing the gas in the retort from coming in con- 

 tact with the heated sides. According to Beilbv, this desired result 

 is obtained by distilling coal with steam. By this method as much 

 as 50 to 56 kg., say 110 to 123-2 lbs., of sulphate of ammonia per 

 ton of coal may be obtained. Gas liquor consists in reality of a weak 

 solution of ammonia, carbonate of ammonia, sulphide of ammonia, 

 cyanide of ammonia, and sulphate of ammonia. Its nitrogen con- 

 tent varies considerably, as the following analvsis bv Arnold, in 

 1889, shows:— 



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