.

You are not yet enough of a chemist to understand that. --But take care,
Caroline, do not approach too near it, for it has a very pungent smell.

I shall show you another instance similar to that of the water, which
you observed to become warmer as it froze. I have in this phial a
solution of a salt called sulphat of soda or Glauber's salt, made very
strong, and corked up when it was hot, and kept without agitation till
it became cold, as you may feel the phial is. Now when I take out the
cork and let the air fall upon it, (for being closed when boiling, there
was a vacuum in the upper part) observe that the salt will suddenly
crystallize. . . .

CAROLINE.

Surprising! how beautifully the needles of salt have shot through the
whole phial!

MRS. B.

Yes, it is very striking--but pray do not forget the object of the
experiment. Feel how warm the phial has become by the conversion of part
of the liquid into a solid.

EMILY.

Quite warm I declare! this is a most curious experiment of the
disengagement of latent heat.

MRS. B.

The slakeing of lime is another remarkable instance of the extrication
of latent heat. Have you never observed how quick-lime smokes when water
is poured upon it, and how much heat it produces?

CAROLINE.

Yes; but I do not understand what change of state takes place in the
lime that occasions its giving out latent heat; for the quick-lime,
which is solid, is (if I recollect right) reduced to powder, by this
operation, and is, therefore, rather expanded than condensed.

MRS. B.

It is from the water, not the lime, that the latent heat is set free.
The water incorporates with, and becomes solid in the lime; in
consequence of which, the heat, which kept it in a liquid state, is
disengaged, and escapes in a sensible form.

CAROLINE.

I always thought that the heat originated in the lime. It seems very
strange that water, and cold water too, should contain so much heat.

EMILY.

After this extrication of caloric, the water must exist in a state of
ice in the lime, since it parts with the heat which kept it liquid.

MRS. B.

It cannot properly be called ice, since ice implies a degree of cold, at
least equal to the freezing point. Yet as water, in combining with lime,
gives out more heat than in freezing, it must be in a state of still
greater solidity in the lime, than it is in the form of ice; and you may
have observed that it does not moisten or liquefy the lime in the
s