The first attempt to find the poisonous constituent of this plant was
made by Khittel in 1857. His work was published in _Wittstein's
Vierteljahrresschrift fuer praktische Pharmacie_, VII, 348-359.[14]
Khittel obtained 37-1/2 ounces of fresh leaves of poison ivy from the
botanical garden in Munich, dried them, and got a residue of 9-1/2
ounces which he analyzed. Not detecting anything to which the poisonous
qualities of the plant could be attributed, he made another series of
experiments which, as he thought, showed that a volatile alkaloid is the
poisonous constituent. It was obtained by the following process: "3
ounces of the powdered leaves were infused with hot distilled water,
after three days strained, expressed, the liquid evaporated to 3 ounces,
and with the addition of potassa, carefully distilled to one-half. The
clear, colorless distillate had an alkaline reaction, and an odor
resembling henbane or hemlock. It was saturated with sulphuric acid,
evaporated, and treated with a mixture of equal quantities of alcohol
and ether which left sulphate of ammonia behind, the solution was
evaporated spontaneously, distilled with potassa, the alkaline
distillate neutralized with hydrochloric acid, and a precipitate could
now be obtained with chloride of platinum. Want of material prevented
further experiments."
The editor of the _American Journal of Pharmacy_ inserts the following
note: "It would have been more satisfactory if the author had given some
physiological evidence of the poisonous nature of the alkaloid
substance obtained. It is quite interesting to hear that the hitherto
intangible venom of this plant has at last been detected."