In the early stages of this work some experiments were made to see if
potassium permanganate could be used to purify the lead precipitate by
oxidizing the tar brought down in precipitation. It was found that the
permanganate attacked the lead precipitate as well as the other organic
matter in the vessel. This fact and the well-known value of permanganate
in treating skin diseases, its use as an antidote for some kinds of
alkaloid poisoning,[47] as an antidote given to cattle poisoned by
plants,[48] and as an antidote for snake bites,[49] suggested its use as
a remedy for Rhus poisoning. Maisch[50] mentioned that he had used it
with success, but it never came into general use, probably on account of
its staining the skin and clothing. In carrying out this work abundant
opportunities for testing its value as a remedy for the dermatitis
caused by poison ivy were afforded by many cases of accidental and
intentional poisoning. The best example of the latter was obtained with
the ether solution from the extraction of the lead precipitate in the
Soxhlet apparatus (page 28). After removing the ether, a small drop of
the residue was applied to the wrist as described. An itching red spot
about the size of a dime was noticed in thirty-six hours, and it
steadily increased in size. Nearly two days after the application of the
poison, a dilute solution of potassium permanganate containing a little
caustic potash was rubbed into the spot until the pimples were
destroyed. A little black spot was left wherever there had been a
pimple, showing that the permanganate had been reduced to oxide in the
skin. The place was washed and nothing more was thought of it until the
morning following, when it was noticed that the wrist had commenced to
swell during the night, and the characteristic watery secretion was
running from the poisoned spot. More permanganate solution was applied
without potash and the wrist was bandaged, thinking that this would
prevent the spreading of the eruption, but it really facilitated
spreading by becoming saturated with the poisonous fluid and keeping it
in contact with a larger surface of skin. In the meantime the swelling
and inflammation had extended nearly to the elbow. The arm now had the
appearance of having been bitten by a snake. To reduce the swelling it
was immersed in hot water. This seemed to bring out the eruption very
quickly and the blisters were treated with permanganate as fast as they
appeared. The swelling was reduced, but returned during the night. On
the evening following, the forearm was immersed in a bowl of hot
permanganate solution containing a little caustic potash. The solution
was kept as hot as could be borne for about half an hour. After this
bath, the poison was completely oxidized, for the swelling was reduced
and did not return, nor was there any fresh eruption. What appeared to
be a severe case of poisoning was thus cured very quickly. The use of
hot water not only reduces the swelling, but also helps to destroy the
poison. The action of permanganate is also more rapid at high
temperatures.
The oxidizing power of permanganate, as is well known, is greater in
acid solution than in alkaline, five atoms of oxygen being available in
the former and three in the latter, according to these equations:
2 KMnO_{4} + 3 H_{2}SO_{4} = K_{2}SO_{4} + 2 MnSO_{4} + 3 H_{2}O + 5 O.
2 KMnO_{4} + H_{2}O = 2 MnO_{2} + 2 KOH + 3 O.
Permanganate was used as a remedy in some cases mixed with dilute
sulphuric acid, and in others, with zinc sulphate; also with lime water.
It was found to be satisfactory whether used alone or with any of the
substances mentioned, provided it was well rubbed into the skin. The
concentration of the solution used was varied according to the location
and condition of the eruption. Where the skin was thin or already
broken, dilute solutions (one per cent.) were used. In one case, the
eruption appeared in the palm of the hand where the skin was so thick
that it was necessary to open it before the remedies could reach the
poison. The difficulty of getting the remedy in contact with the poison
in the skin is the reason why the eruption is hard to cure.
The remedy most commonly used for this eruption is an alcoholic solution
of lead acetate. This remedy is unsatisfactory for the reason that its
action consists in depositing an unstable lead compound of the poison in
the skin where the conditions of moisture and temperature are favorable
for its decomposition, liberating the poison with all its irritant
properties. Moreover, alcoholic preparations should not be used because
the alcohol dissolves the poison and, on evaporation, leaves it spread
over a larger surface like a varnish. Potassium permanganate, however,
oxidizes the poison completely. The only objection to the use of
permanganate of which the writer is aware is that it stains the skin.
The stain can be removed by vigorous scrubbing with soap, or it will
wear off gradually in a few days. It can be removed at once by certain
acids, but these should not be used by persons not familiar with their
action.
With the knowledge of the facts mentioned, many solutions were tested
for poison by applying them to the skin, and when an eruption appeared,
it was cured quickly and permanently by rubbing in a permanganate
solution, usually mixed with dilute sulphuric acid.