s that of evolving a considerable
quantity of heat when mixed with water; this I have already shown you.

EMILY.

Yes, I recollect it; but what was the degree of heat produced by that
mixture?

MRS. B.

The thermometer may be raised by it to 300 degrees, which is
considerably above the temperature of boiling water.

CAROLINE.

Then water might be made to boil in that mixture?

MRS. B.

Nothing more easy, provided that you employ sufficient quantities of
acid and of water, and in the due proportions. The greatest heat is
produced by a mixture of one part of water to four of the acid: we shall
make a mixture of these proportions, and immerse in it this thin glass
tube, which is full of water.

CAROLINE.

The vessel feels extremely hot, but the water does not boil yet.

MRS. B.

You must allow some time for the heat to penetrate the tube, and raise
the temperature of the water to the boiling point--

CAROLINE.

Now it boils--and with increasing violence.

MRS. B.

But it will not continue boiling long; for the mixture gives out heat
only while the particles of the water and the acid are mutually
penetrating each other: as soon as the new arrangement of those
particles is effected, the mixture will gradually cool, and the water
return to its former temperature.

You have seen the manner in which sulphuric acid decomposes all
combustible substances, whether animal, vegetable, or mineral, and burns
them by means of its oxygen?

CAROLINE.

I have very unintentionally repeated the experiment on my gown, by
letting a drop of the acid fall upon it, and it has made a stain, which,
I suppose, will never wash out.

MRS. B.

No, certainly; for before you can put it into water, the spot will
become a hole, as the acid has literally burnt the muslin.

CAROLINE.

So it has, indeed! Well, I will fasten the stopper, and put the bottle
away, for it is a dangerous substance. --Oh, now I have done worse
still, for I have spilt some on my hand!

MRS. B.

It is then burned, as well as your gown, for you know that oxygen
destroys animal as well as vegetable matters; and, as far as the
decomposition of the skin of your finger is effected, there is no
remedy; but by washing it immediately in water, you will dilute the
acid, and prevent any further injury.

CAROLINE.

It feels extremely hot, I assure you.

MRS. B.

You have now learned, by experience, how cautiously this acid must be
used. You will soon