EUPEORBIACEJEJ. 285 



non-vesicating part. The author has endeavoured to ascertain to 

 what constituent of the soluble portion of the oil the vesicating 

 properties are due, and has traced these properties to the non- 

 volatile fatty acids, chiefly to those which have the lowest 

 melting points, are least readily saponified by alkalies, and are 

 first liberated when the alkali soap is decomposed by acids. 

 He attributes the purgative action not to the free acids, but 

 to the combination in which they e3:ist in the oil. 



These conclusions not appearing satisfactory to Professor 

 Kobert, the investigation was taken up by Herr von Hirsch- 

 heydt, a pupil in the University of Dorpat. Upon the basis 

 of the results obtained, Professor Kobert now ( Chem. Zeit., 

 April 6, 1887^ p. 416) attributes the activity of croton oil, both 

 as a vesicant and as a purgative, to crotonoleic acid, not to be 

 confounded with crotonic acid, but an acid discovered by Buch- 

 heim in 1873, to which a formula has not yet been assigned. 

 This crotonoleic acid is said to occur in croton oil both in the 

 free state, in which it is freely soluble in alcohol, and in 

 combination as a glyceride. The glyceride does not possess 

 poisonous properties, but the free acid acts as a powerful 

 irritant to the skin and the intestines (purgative) . According 

 to Professor Kobert, the crotonolglyceride is attacked and 

 split up like other glycerides by the ferments of the juices of 

 the stomach, and the crotonoleic acid being set free then 

 exercises its purgative influence. A similar result may be 

 obtained by administering crotonoleic acid as a pill enclosed in 

 keratin. Kobert is not of opinion, however, that the solubility 

 of croton oil is dependent upon the proportion of crotonoleic 

 acid it contains, but considers it to be connected with the age 

 of the oil. Crotonoleic acid may be prepared by treating the 

 portion of croton oil soluble in alcohol with a hot saturated 

 solution of baryta in a water-bath, washing the stiff white paste 

 that forms with cold distilled water to remove excess of baryta 

 and barium compounds with acetic, butyric and tiglinic acid 

 removing by heat traces of water, and repeatedly treating with 

 ether, which only takes up the barium oleate and crotonoleate. 

 The crotonoleate is separated by dissolving it out in alcohol^ 



