and then blow steam at 100° C. (212° F.) into that water, the latter
will boil not at 212° F., but at a higher temperature. There is a
certain industrial process I know of, in course of which it is necessary
first to maintain a vessel containing water, by means of a heated closed
steam coil, at 212° F. (100° C.), and at a certain stage to raise the
temperature to about 327° F. (164° C.). The pressure on the boiler
connected with the steam coil is raised to nearly seven atmospheres, and
thus the heat of the high-pressure steam rises to 327° F. (164° C.), and
then a considerable quantity of nitrate of ammonium, a crystallised
salt, is thrown into the water, in which it dissolves. Strange to say,
although the water alone would boil at 212° F., a strong solution in
water of the ammonium nitrate only boils at 327° F., so that the effect
of dissolving that salt in the water is the same as if the pressure were
raised to seven atmospheres. Now let us, as hat manufacturers, learn a
practical lesson from this fact. We have observed that wool and fur
fibres are injured by boiling in pure water, and the heat has much to do
with this damage; but if the boiling take place in bichrome liquors or
similar solutions, that boiling will, according to the strength of the
solution in dissolved matters, take place at a temperature more or less
elevated above the boiling-point of water, and so the damage done will
be the more serious the more concentrated the liquors are, quite
independently of the nature of the substances dissolved in those
liquors.

_Solution._--We have already seen that when a salt of any kind dissolves
in water, heat is absorbed, and becomes latent; in other words, cold is
produced. I will describe a remarkable example or experiment, well
illustrating this fact. If you take some Glauber's salt, crystallised
sulphate of soda, and mix it with some hydrochloric acid (or spirits of
salt), then so rapidly will the solution proceed, and consequently so