Water should then be considered as one of the elements of
leather, but it must be understood that if it exceeds certain limits,
say 12 to 14 per cent., it becomes useless and even injurious. Moreover,
if there is any excess over the normal quantity, it becomes deceptive
and dishonest, as in such a case one sells for hides that which is
nothing but water. Supposing that a hide, instead of only 14 per cent.,
contained 18 per cent. of water, it is evident that in buying 100 pounds
of such a hide one would pay for four pounds of water at the rate for
which he purchased the hide.
There are, also, some matters soluble in air, which are formed to a
large extent from fat arising as much from the hide as from tanning
substances. The air dissolves at the same time a certain amount of
organic acid and resinous products which the hide has absorbed. After
treating with air, alcohol is used, which dissolves principally the
coloring matters, tannin which has not become assimilated, bodies
analogous to resin, and some extractive substances.
That which remains after these methods have been pursued ought to be
regarded as the hide proper, that is to say, as the animal tissue
saturated with tannic acid. In this remainder one is able to estimate
with close precision that which belongs to the hide. The hide being an
elementary tissue of unchangeable form, it is easy, in determining the
elementary portion, to find the amount of real hide remaining in the
product.
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