This salt occurs in small crystals, whose form is that of a four sided
prism. It is extremely acid to the taste, so that by applying the tongue
to one of its crystals, its nature may be immediately discovered. It
dissolves in twice its weight of cold, and in an equal weight of hot
water; it is also soluble in boiling alcohol which takes up about half
its weight; the solutions act powerfully on the vegetable colours, and
at once denote their acid properties. On account of the strong
resemblance which the crystals of this acid bear to those of sulphate of
magnesia, or _Epsom_ salts, many fatal accidents have occurred. We are
not aware that it is ever purchased, in retail, for any other purpose
than as a detergent, to clean the tops of boots; in the large way, it is
an article of extensive trade with the calico printers. Its salts[326]
are likewise employed for various purposes in the arts.
Amongst the many schemes which have been proposed to secure the public
against the possibility of mistaking this acid for Epsom salts, there
does not appear to be one which admits of successful application; nor
are we able to propose any test of discrimination which is not far
inferior in accuracy and convenience, to that which is afforded by the
mere taste of the crystal; indeed we cannot understand how so acid a
solution can be swallowed, without an immediate discovery.
_Symptoms of Poisoning by Oxalic Acid._
From the history of the many cases on record, it appears that this acid
produces all the grievous symptoms, which characterise the action of a
corrosive poison; its operation upon the stomach is similar to that of
any other powerful acid; and dissection displays the same destruction of
parts, as that we have already described under the consideration of the
mineral acids.
_Antidotes._
We should endeavour to form as quickly as possible an insoluble oxalate
of lime; copious draughts of lime water, or magnesia and water, should
be administered; and vomiting immediately excited.
_Chemical tests for the detection of Oxalic Acid._
If any of its crystals can be obtained, we shall be immediately able to
identify them. They dissolve very readily in water, and since the oxalic
has a greater affinity for lime, than any other acid, and forms an
insoluble salt with it, we have thus a ready test of its presence, for
it will decompose all the calcareous salts, not even excepting the
sulphate.