Nature of the Vesicating Constituent of Croton Oil. 245 



of alcohol (70 per cent.). The oil is allowed to settle, and the alcohol 

 decanted. The residual oil is again twice extracted with alcohol in 

 the same manner. The mixed alcoholic solutions are then distilled to 

 a small volume and the oil saponified by heating it on the water bath 

 with a mixture of freshly precipitated lead oxide and water. The 

 lead soap is thoroughly washed with warm water, mixed with white 

 sand, dried, powdered, and percolated with warm alcohol. Dilute 

 alcohol (25 per cent.) removes the resin almost pure ; but the entire 

 extraction of the active constituent takes a long time, and we have 

 found it in the eud shorter to extract with strong alcohol (70 per 

 cent.), which dissolves also a little lead oleate, and then to purify the 

 resin by fractional precipitation of the alcoholic solution with water. 

 The first fraction usually contains the whole of the lead salt, and the 

 later fractions furnish a pale yellow, hard, brittle resin, which is 

 generally quite pure, or needs but one repetition of the process of 

 fractional precipitation to make it so. Croton-resin is a pale yellow, 

 brittle, nearly transparent substance, which is easily reduced to a 

 fine powder. Numerous attempts have been made in various ways to 

 crystallise it, or to separate some crystalline substance from it, but 

 in every case without success. It contains carbon, hydrogen, and 

 oxygen, but no nitrogen. Its homogeneity and composition have been 

 established by the analyses of various specimens representing different 

 fractions obtained by the addition of small quantities of water to its 

 alcoholic solution. A specimen of the resin, which had been frac- 

 tionated in the manner described, was dissolved in dry ether, and the 

 ethereal solution evaporated in a large flat-bottomed dish. The thin 

 film thus formed was heated for two hours in the water bath and 

 then exposed for some weeks in a vacuous desiccator over sulphuric 

 acid. A portion of this specimen (A) was burned in two parts, with 

 the following results : — 



I. Weight of resin 0*2009 



Weight of water . . 0*1496 



Weight of carbon dioxide . . 0*4902 



C = 66*55 per cent. ; H = 8'26 per cent. 



II. Weight of resin 0*18 



Weight of water 0*1296 



Weight of carbon dioxide . . 0*438 



C = 66*4 per cent. ; H. = 8 per cent. 



Mean for A — 



C = 66*45 per cent ; H = 8*13 per cent. 



The remainder of the specimen was dissolved in alcohol, and the 



