t derives
the oxygen which burns it from the atmosphere, or from any other source,
the chemical effect on the wood is the same. In the case of real
combustion, wood becomes black, because it is reduced to the state of
charcoal by the evaporation of its other constituents. But can you tell
me the reason why wood turns black when burnt by the application of an
acid?

CAROLINE.

First, tell me what are the ingredients of wood?

MRS. B.

Hydrogen and carbon are the chief constituents of wood, as of all other
vegetable substances.

CAROLINE.

Well, then, I suppose that the oxygen of the acid combines with the
hydrogen of the wood, to form water; and that the carbon of the wood,
remaining alone, appears of its usual black colour.

MRS. B.

Very well indeed, my dear; that is certainly the most plausible
explanation.

EMILY.

Would not this be a good method of making charcoal?

MRS. B.

It would be an extremely expensive, and, I believe, very imperfect
method; for the action of the acid on the wood, and the heat produced by
it, are far from sufficient to deprive the wood of all its evaporable
parts.

CAROLINE.

What is the reason that vinegar, lemon, and the acid of fruits, do not
produce this effect on wood?

MRS. B.

They are vegetable acids, whose bases are composed of hydrogen and
carbon; the oxygen, therefore, will not be disposed to quit this
radical, where it is already united with hydrogen. The strongest of
these may, perhaps, yield a little of their oxygen to the wood, and
produce a stain upon it; but the carbon will not be sufficiently
uncovered to assume its black colour. Indeed, the several mineral acids
themselves possess this power of charring wood in very different
degrees.

EMILY.

Cannot vegetable acids be decomposed, by any combustibles?

MRS. B.

No; because their radical is composed of two substances which have a
greater attraction for oxygen than any known body.

CAROLINE.

And are those strong acids, which burn and decompose wood, capable of
producing similar effects on the skin and flesh of animals?

MRS. B.

Yes; all the mineral acids, and one of them more especially, possess
powerful caustic qualities. They actually corrode and destroy the skin
and flesh; but they do not produce upon these exactly the same
alteration they do on wood, probably because there is a great proportion
of nitrogen and other substances in animal matter, which prevents the
separation of carb