SOOT—GAS LIQUOR.

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452. In connexion with ashes, soot and the refuseof gas-works may be mentioned, although very differentin their nature. Soot consists principally of finely-divided charcoal or carbon, but it contains a considerablequantity of salts of ammonia; hence it is a powerfuland valuable manure. If a little quicklime is mixedwith soot, the salts of ammonia will be decomposed, andthe strong pungent smell of ammonia is evident.

453. Soot contains a good deal of the ammoniaobtained during the combustion of coal, but, in conse-quence of its volatility, a considerable portion is lost. Inthe process for making gas, where coal is roasted in closeiron vessels, all the ammonia is saved, and is condensedby means of cold water. The gas is made to bubblethrough a quantity of water: this condenses the am-monia, and constitutes what is termed gas liquor, or theammoniacal liquor of the gas-works. It is a solutionof ammonia, partly caustic, and partly combined withcarbonic acid and sulphuretted hydrogen (118).

454. Ammoniacal liquor is a strong and excellentmanure, resembling in some respects the manures formedby the decay of animal substances. As obtained fromthe gas-works it is almost always too strong to be usedas a manure for grass-lands or crops, and must be dilutedwith four or six times its bulk of water.

455. In consequence of the volatility and causticnature of free ammonia, it is found advisable for mostpurposes to fix the ammonia of gas liquor. This mayeither be done with an acid, or with gypsum or sulphate