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original coal. From this the most useful practical results 
accrue. The volatile constituents might he separated from 
the coke, and the latter applied with equal economic effect 
in our manufactures, without the emission of that smoke 
which at present is so fatal to the health and comfort of 
our towns. The volatile combustible substance might, by 
an enlarged system of gas manufacture, be extensively 
employed for the development of domestic heat, as well 
as for illuminating purposes. 
The ammonia, which we have seen to be an important 
product of the distillatory process, is at present discharged 
into the atmosphere. By the most simple arrangement, 
however, in the coke ovens, the ammoniacal vapours might 
be economised, and under the form of sulphate of ammonia 
form a most valuable commercial article. An ingenious 
patent has recently been taken out by Mr. Crole, of the 
Tottenham Gas Works, by which he passes the gas through 
a weak solution of sulphuric acid ; the ammonia in the gas 
unites with the acid, forming sulphate of ammonia, and the 
gas, after the separation, is increased five per cent, in 
illuminating power. The solution of sulphate of ammonia 
is then evaporated down to dryness, every gallon of the 
liquor yielding 80 oz. of the salt. It has been estimated 
that 100 tons of coal, in coking, is capable of producing on 
the average six tons of sulphate of ammonia, NH^, SO^ -|- HO, 
and the commercial price of that salt for the purposes of a 
manure is £13 a ton. A still more beneficial process is, 
perhaps, that of purifying the gas by phosphate of lime, 
containing some sulphuric acid, as obtained by the action of 
oil of vitriol upon bone earth. The product, — phosphate of 
lime and ammonia,— containing some sulphate of ammonia, 
forms a still more valuable manure than sulphate of ammonia 
alone. 
The application of coal gas for the production of heat 
