SECT. XXVI.--_Observations upon Tartarous Acid, and its Combinations._
Tartar, or the concretion which fixes to the inside of vessels in which
the fermentation of wine is completed, is a well known salt, composed of
a peculiar acid, united in considerable excess to potash. Mr Scheele
first pointed out the method of obtaining this acid pure. Having
observed that it has a greater affinity to lime than to potash, he
directs us to proceed in the following manner. Dissolve purified tartar
in boiling water, and add a sufficient quantity of lime till the acid be
completely saturated. The tartarite of lime which is formed, being
almost insoluble in cold water, falls to the bottom, and is separated
from the solution of potash by decantation; it is afterwards washed in
cold water, and dried; then pour on some sulphuric acid, diluted with
eight or nine parts of water, digest for twelve hours in a gentle heat,
frequently stirring the mixture; the sulphuric acid combines with the
lime, and the tartarous acid is left free. A small quantity of gas, not
hitherto examined, is disengaged during this process. At the end of
twelve hours, having decanted off the clear liquor, wash the sulphat of
lime in cold water, which add to the decanted liquor, then evaporate
the whole, and the tartarous acid is obtained in a concrete form. Two
pounds of purified tartar, by means of from eight to ten ounces of
sulphuric acid, yield about eleven ounces of tartarous acid.
As the combustible radical exists in excess, or as the acid from tartar
is not fully saturated with oxygen, we call it _tartarous acid_, and the
neutral salts formed by its combinations with salifiable bases
_tartarites_. The base of the tartarous acid is a carbono-hydrous or
hydro-carbonous radical, less oxygenated than in the oxalic acid; and it
would appear, from the experiments of Mr Hassenfratz, that azote enters
into the composition of the tartarous radical, even in considerable
quantity. By oxygenating the tartarous acid, it is convertible into
oxalic, malic, and acetous acids; but it is probable the proportions of
hydrogen and charcoal in the radical are changed during these
conversions, and that the difference between these acids does not alone
consist in the different degrees of oxygenation.
The tartarous acid is susceptible of two degrees of saturation in its
combinations with the fixed alkalies; by one of these a salt is formed
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