CHAPTEE XIV. 



RECOVERY OF NITROGEN FROM DISTILLERY SPENT WASH. 

 MANUFACTURE OF CYANAMIDE AND OF NITRATE OF LIME. 



Utilization of Spent Wasli. — General Bemarks. — The question of 

 the utiUzation of distillery spent wash, looking to its great economi- 

 cal importance, has engaged the attention of chemists for a long 

 time. In grain distilleries the dregs are generally filtered, then 

 dried ; the spent wash which flows therefrom contains 80 to 100 

 grm. of nitrogen per hectolitre ; and as 100 kg. of grain yield 

 about 3 hectolitres of liquid, the loss of nitrogen is 1 to l-2o6 kg. 

 per hectolitre of alcohol manufactured, say 1 to 1\ lb. per 10 gal. of 

 100 per cent alcohol. In beet distilleries the loss in nitrogen is also 

 very considerable ; the fermented wash issuing from the distilling 

 column contains 100 to 160 grm. of nitrogen per hectolitre. 

 Finally, the spent wash from the distillation of molasses and sucrate 

 liquors contains 1'4 per cent of nitrogen and 9 per cent of salts. 

 Now, if the spent wash be simply incinerated, to extract the salts 

 from it according to a process already old, all the nitrogen, of which 

 the money value is superior to that of the potash, is lost. If in a 

 molasses distillery they calculate on a yield of 9 per cent of salts, 

 it will be seen that there is extracted from 1000 kg. (a metric 

 ton) of molasses 90 kg. of salts, say 198 lb., at 40 per cent of car- 

 bonate, worth 38 centimes the degree, say 13-68 francs, say lis., 

 and that there is lost by incineration all the nitrogen, of which 

 75 per cent at least is recoverable, say 11 kg. (22-42 lb.), worth 1-50 

 francs the degree, say 16-50 francs, or 13s. 2d. 



It will be seen that the problem of the recovery of nitrogen 

 from these residues deserves to attract in the highest degree the 

 attention of distillers. Different processes have been proposed to 

 recover this nitrogen. Attempts have been made to recover it by dry 

 distillation as ammoniacal salts or liquor ammonia. There is then 

 obtained a complex liquid containing tars, methylamines, and other 

 bodies difficult to purify. These processes have not been adopted 

 in actual practice, which would tend to the belief that the financial 

 results did not conform with those which bad been expected. 

 Attempts were also made to prepare compound manures from 

 spent wash by adding precipitated phosphate of lime, and inert 



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