tment of these with lime, or, as
it is chemically known, oxide of calcium, ammonia is set free, whilst
chloride of lime (the well-known disinfectant), or sulphate of lime
(gypsum, or "plaster of Paris" ), is the result.

Thus:

Sulphate of ammonia + lime = plaster of Paris + ammonia.

or,

Sal-ammoniac + lime = chloride of lime + ammonia.

Ammonia itself is a most powerful gas, and acts rapidly upon the eyes. It
has a stimulating effect upon the nerves. It is not a chemical element,
being composed of three parts of hydrogen by weight to one of nitrogen,
both of which elements alone are very harmless, and, the latter indeed,
very necessary to human life. Ammonia is fatal to life, producing great
irritation of the lungs.

It has also been called "hartshorn," being obtained by destructive
distillation of horn and bone. The name "ammonia" is said to have been
derived from the fact that it was first obtained by the Arabs near the
temple of Jupiter Ammon, in Lybia, North Africa, from the excrement of
camels, in the form of sal-ammoniac. There are always traces of it in the
atmosphere, especially in the vicinity of large towns and manufactories
where large quantities of coal are burned.

Coke, if properly prepared, should consist of pure carbon. Good coal
should yield as much as 80 per cent. of coke, but owing to the
unsatisfactory manner of its production, this proportion is seldom
yielded, whilst the coke which is familiar to householders, being the
residue left in the retorts after gas-making, usually contains so large a
proportion of sulphur as to make its combustion almost offensive. No
doubt the result of its unsatisfactory preparation has been that it has
failed to make its way into households as it should have done, but there
is also another objection to its use, namely, the fact that, owing to the
quantity of oxygen required in its combustion, it gives rise to feelings
of suffocation where insufficient ventilation of the room is provided.

Large quantities of coke are, however, consumed in the feeding of furnace
fires, and in the heating of boilers of locomotives, as well as in
metallurgical operations; and in order to supply the demand, large
quantities of coal are "coked," a process by which the volatile products
are completely combusted, pure coke remaining behind. This process is
therefore the direct opposite to that of "distillation," by which the
volatile products are carefully collected and re-distille