the latent heat of steam is 536 heat units.

_Effect of Increase of Pressure on the Boiling of Water._--Now we have
referred to diminution of pressure and its effect on the boiling-point
of water, and I may point out that by increasing the pressure, such,
_e.g._, as boiling water under a high pressure of steam, you raise the
boiling-point. There are some industrial operations in which the action
of certain boiling solutions is unavailing to effect certain
decompositions or other ends when the boiling is carried on under the
ordinary atmospheric pressure, and boiling in closed and strong vessels
under pressure must be resorted to. Take as an example the wood-pulp
process for making paper from wood shavings. Boiling in open pans with
caustic soda lye is insufficient to reduce the wood to pulp, and so
boiling in strong vessels under pressure is adopted. The temperature of
the solution rises far above 212 deg. F. (100 deg. C.). Let us see what may
result chemically from the attainment of such high temperatures of water
in our steam boilers working under high pressures. If you blow ordinary
steam at 212 deg. F. or 100 deg. C., into fats or oils, the fats and oils remain
undecomposed; but suppose you let fatty and oily matters of animal or
vegetable origin, such as lubricants, get into your boiler feed-water
and so into your boiler, what will happen? I have only to tell you that
a process is patented for decomposing fats with superheated steam, to
drive or distil over the admixed fatty acids and glycerin, in order to
show you that in your boilers such greasy matters will be more or less
decomposed. Fats are neutral as fats, and will not injure the iron of
the boilers; but once decompose them and they are split up into an acid
called a fat acid, and glycerin. That fat acid at the high temperature
soon attacks your boilers and pipes, and eats away the iron. That is one
of the curious results that may follow at such high temperatures.
Mineral or hydrocarbon oils do not contain these fat acids, and so
cannot possibly, even with high-pressure steam, corrode the boiler
metal.

_Effect of Dissolved Salts on the Boiling of Water._--Let us inquire
what this effect is? Suppose we dissolve a quantity of a salt in water,
and then blow steam at 100 deg. C. (212 deg. F.) into that water, the latter
will boil not at 212 deg. F., but at a higher temperature. There is a
certain industrial process I know of, in course of which it is necessar