"nitrification," and there is very
good reason for believing that this transformation is the work of a
micro-organism present in the soil. The gas liquor thus supplies food to a
minute organism which converts the ammonia into a form available for the
higher plants. Some branches of agriculture--such as the cultivation of
the beet for sugar manufacture--are so largely dependent upon an
artificial source of nitrogen, that their very existence is bound up with
the supply of ammonia salts or other nitrogenous manures. The relationship
between the manufacture of beet-sugar and the distillation of coal for the
production of gas is thus closer than many readers will have imagined; for
while the supply of native guano or nitrate is uncertain, and its freight
costly on account of the distance from which it has to be shipped, the
sulphate of ammonia from gas-liquor is always at hand, and available for
the purposes of fertilization.

Then again, there are other products of industrial value which are
associated with ammonia, such, for example, as ammonia-alum and caustic
soda. This last is one of the most important chemical compounds
manufactured on a large scale, and is consumed in enormous quantities for
the manufacture of paper and soap, and other purposes. Salts of this
alkali are also essential for glass making. Of late years a method for the
production of caustic soda has been introduced which depends upon the use
of ammonia, and as this process is proving a formidable rival to the older
method of alkali manufacture, it may be said that such indispensable
articles as paper, soap, and glass are now to some extent dependent upon
gas-liquor, and may in course of time become still more intimately
connected with the manufacture of coal-gas.

But quantitative statements must be given in order to bring home to
general readers the actual value of the small percentage of nitrogen
present in coal. Thus it has been estimated, that one ton of coal gives
enough ammonia to furnish about 30 lbs. of the crude sulphate. The present
value of this salt is roughly about L12 per ton. The ten million tons of
coal distilled annually for gas making would thus give 133,929 tons of
sulphate, equal in money value to L1,607,148, supposing the whole of the
ammonia to be sold in this form. To this may be added the ammonia obtained
during the distillation of shale and the carbonization of coal for coke,
the former source furnishing about 22,000 tons, and t