LIQUOR OF GAS-WORKS. 205 



being diluted to such a degree as to be tasteless, is 

 applied as a manure to the field.* 



Now, the ammoniacal liquor of the gas-works con- 

 tains the ammonia in the form of carbonate and 

 hydro-sulphate of ammonia (sulphuret of ammonium). 

 The latter compound is a deadly poison to vegeta- 

 bles, nor can we conceive that by dilution its prop- 

 erties can be changed. The carbonate of ammonia 

 is volatile, and escapes into the atmosphere. To 

 obviate this latter inconvenience and render it more 

 transportable, it has been proposed to convert the 

 carbonate into the sulphate, by means of gypsum, f 

 But this does not remove the hydro-sulphate. A 

 more simple and efficacious method is to add a solu- 

 tion of sulphate of iron (the green vitriol of the shops) 

 to the liquor, until no further precipitation ensues. 

 Sulphuret and carbonate of iron are thus formed, 

 and the whole of the ammonia enters into combina- 

 tion wuth the sulphuric acid, and forms sulphate of 

 ammonia. Care must be taken to avoid too great an 

 excess of sulphate of iron ; and the liquor thus pre- 

 pared should be freely exposed to the air to promote 

 the oxidation. 



The liquor still, however, contains empyreumatic 

 matters, which are injurious to plants. These may 

 be removed by evaporating the liquor to dryness, 

 and heating the residue to incipient redness. By 

 this means they are rendered insoluble, and the sul- 

 phate of ammonia is not affected, unless the heat has 

 been carried too far. The liquor properly diluted 

 has been found very advantageous, even without the 

 removal of the empyreumatic matter. 



* Mr. Blake, who has charge of the gas- work in Boston, informs me, 

 that one chaldron (2700 lbs. of Pictou coal, yields, on the average, 33 

 gallons of ammoniacal liquor containing about 5 per cent, of dry am- 

 monia ; and by passing the gases generated from this quantity of coal 

 through a solution of proto-sulphate of iron, he has obtained in addition 

 24 gallons of a solution containing about 4 per cent, of dry ammonia. 

 About 4 chaldrons of coal are used per diem, at the gas-works in Bos- 

 ton, and 200 gallons of liquor, containing from 4 to 5 per cent, of am- 

 monia, could be furnished daily at small cost. — W, 



t Three Lectures on Agriculture, by Dr. Daubeny, page 87. 



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