[7] Ann. de Chem. et de Phys., Series VII, Vol. 12, p. 125, 1897.
[8] Amer. Jour. Pharm. 78, p. 53, Feb., 1906.
[9] An account of Pfaff's work will be found in another part of this paper.
[10] Amer. Jour. Med. Sci. 51 (1866), p. 560.
[11] Med. and Surg. Rep. 17, Nov., 1867.
[12] Jour. Exp. Med. 2 (1897), p. 181.
[13] Ibid.
KHITTEL'S INVESTIGATION.
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 für 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."