THE CORROSIVE VEGETABLE ACIDS.
OXALIC ACID (_Acid of Sugar_).--This is one of the most important
poisons with which we have to deal. From its cheapness and well-known
properties it is frequently made use of in cases of suicide, while from
its resemblance to Epsom salts it has on several occasions been taken in
mistake for that medicine. The smallest dose which is known to have
proved fatal is one drachm, which killed a boy aet. sixteen in eight
hours. Taylor relates the case of a woman, aged twenty-eight, who was
found dead one hour after swallowing three drachms of the crystallized
acid. Christison mentions an instance in which one ounce destroyed life
in ten minutes, and another case where the same quantity killed a girl
in thirty minutes. One example has been recorded where a fatal result
ensued probably within three minutes of the acid being swallowed.
The poisonous properties of the _Binoxalate of Potash_ (Salt of Sorrel,
Essential Salt of Lemons) are due to the oxalic acid it contains. This
salt, which exists in the leaves of the wood sorrel (Oxalis acetosella),
is sold to bleach straw, remove ink-stains, &c. It is very cheap; is
almost as powerful as oxalic acid itself, and gives rise to the same
kind of symptoms; it has been taken for the purpose of suicide, as well
as in mistake for the bitartrate of potash, or cream of tartar.
Oxalate of lime exists in considerable quantity in the leaves and stalks
of the common edible rhubarb (Rheum Rhaponticum). It can hardly be
considered poisonous.
_Symptoms._--The effects of poisoning by oxalic acid are peculiar. When
the dose is large (half an ounce or more) and the solution concentrated,
it proves very rapidly fatal. It produces a hot burning sensation in the
fauces and oesophagus in the act of swallowing, severe burning pain in
the stomach, and in most instances immediate vomiting. The vomited
matters are strongly acid, of a dirty green or black color, and consist
of the contents of the stomach with altered mucus and blood. The
remaining symptoms are a sense of constriction or suffocation, lividity
of the countenance, great prostration of strength, feeble pulse, cold
clammy perspirations, and convulsions, which speedily terminate in
death. When a smaller quantity has been taken, much diluted, its
corrosive properties are weakened or destroyed, but the nervous
symptoms, as cramps and numbness, may be well marked.
In cases of recovery the mouth may remain sore for some time, the tongue
swollen, the abdomen tender, the stomach very irritable, and there may
be troublesome diarrhoea. In two instances there has been loss of
voice for several days, owing to the action of the poison on the nervous
system. Twitching of the muscles of the face and extremities has also
been observed.
_Post-mortem Appearances._--The mucous membrane of the fauces,
oesophagus, and stomach is generally white and brittle, but often
colored with the brown mucous matter discharged. The stomach often
contains a black fluid, like coffee-grounds, consisting principally of
altered blood; and its sub-mucous coats are vascular and dark colored.
The stomach though seldom perforated, may yet be so softened as to be
with difficulty removed entire, and sometimes this is not possible. This
softening may be due to the post-mortem action of the poison; but its
effects during life in softening and bleaching the mucous membrane are
sufficiently marked. Occasionally the stomach is black and gangrenous
looking. If death has occurred quickly, the small intestines are seldom
much affected; but where the symptoms have been protracted there are
usually signs of congestion and inflammation.
_Treatment._--Chalk, whiting, or magnesia, suspended in water, or in
some demulcent fluid, must be administered immediately; and if
necessary, vomiting should be excited by tickling the fauces, or
administering emetics of sulphate of zinc and ipecacuan, followed by
large quantities of emollient drinks. The antidote, to be effective,
must be given as soon as possible, the plaster of the apartment, or any
form of mortar being used in the absence of the remedies just mentioned.
Alkalies (soda, potash, or their carbonates) are not only useless, but
they form salts with oxalic acid, which are as injurious as the acid
itself. When there are symptoms of collapse, stimulants are to be freely
employed.
From the tendency to softening, the stomach-pump should not be used.
_Tests._--Crystals of oxalic acid are met with as four-sided prisms,
colorless, without odor permanent in the air, and very acid; this last
character distinguishing them from crystals of sulphate of magnesia and
sulphate of zinc. The crystals, when heated, melt, and are dissipated
without combustion, and leaving no residue. This character is important
as a means of distinguishing oxalic acid from other similar crystals.
They are soluble in from eight to twelve parts of cold water. This acid
may be thus recognised in solution:
1. _Nitrate of silver_ throws down, with oxalic acid, an abundant white
precipitate (oxalate of silver), which is soluble in nitric acid. The
oxalate of silver, when dried and heated on platinum foil, detonates,
and is dissipated in a white vapor.
2. _Sulphate of calcium_ causes a white precipitate with oxalic acid
(oxalate of calcium) which is soluble in nitric or hydrochloric, but not
in any vegetable acid.
The solution containing the acid should be concentrated before testing,
if it be not present in considerable quantity.
Lime water and all soluble lime salts throw down precipitates with
oxalic acid; but as these are liable to be mistaken for a precipitate
with sulphuric acid, it is better to use sulphate of calcium which is
slightly soluble, as the test agent. A good deal of the test solution
must be used, and the precipitate takes time to settle.
3. _Sulphate of copper_ gives a faint bluish precipitate with oxalic
acid (oxalate of copper), which is not redissolved by a few drops of
hydrochloric acid.
These tests will not act if the solution contain nitric acid in excess,
in which case the liquid must be evaporated to crystallization, and the
crystals washed and redissolved in water.
These tests for oxalic acid should never be applied without previously
separating it from all organic matter. This is best done by first of all
acidulating the suspected fluid with acetic acid, and then adding
acetate of lead, which combines with the oxalic acid to form a white
insoluble salt, which may ordinarily be removed by filtration or
subsidence. This filtrate, after being well washed, is to be diffused in
water, and into this a current of sulphuretted hydrogen gas is to be
passed for some considerable time. This will throw down the lead as
sulphide, leaving the oxalic acid in the fluid; any organic matter will
also be carried down. Filtration will separate the solids from the
liquid containing the acid, which may now be evaporated until crystals
are formed, which may be tested in the usual way.
ACETIC ACID.--Although this acid, in its concentrated state, is highly
corrosive, yet it is very seldom brought under the notice of the
toxicologist.
In the case of a young woman reported by Orfila, death quickly occurred
after several attacks of convulsions. At the subsequent post-mortem
examination, the integuments of the dependent parts of the body were
found very livid; the tongue and oesophagus were of a dirty brown
color, the latter being intersected by a fine net-work of capillary
vessels; and the interior of the stomach was interspersed with black
elevations caused by the presence of coagulated blood in the sub-mucous
areolar tissue. The mucous membrane was entire.
As regards the _treatment_, it is only necessary to administer draughts
containing magnesia or its carbonate, followed by mucilaginous or
demulcent drinks.
TARTARIC ACID, though not a corrosive, may be here placed along with the
other vegetable acids. Strange as it may seem, tartaric acid has
destroyed life in at least one instance in this country; an ounce having
been given in mistake for an aperient salt. The deceased swallowed the
whole at once, and immediately called out that he had been poisoned. He
complained of intense pain in the throat and stomach, as if he had
swallowed oil of vitriol, or was on fire. Soda and magnesia were
administered without avail; and after death, at the end of nine days'
suffering, the stomach and intestines were found much inflamed.