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Mr. W. R. Dimstan and Miss L. E. Boole. 



croton resin, leaving an inactive solution of sodium salts. The resin 

 thus obtained was purified by dissolving it in alcohol and fraction- 

 ally precipitating the solution with water. The last fraction was 

 extremely active and when dry become a pale yellow, brittle, resinous 

 mass devoid of acid properties. It was therefore conclusively proved 

 that the so-called crotonoleic acid, hitherto regarded as the active 

 constituent of croton oil, is a mixture of fatty acids, chiefly oleic 

 acid, with croton-resin, which is the true vesicating constituent of 

 croton oil. 



Preparation, Properties, and Composition of Croton-resin. 



The method by which the resin was first isolated has already been 

 described. It was found advantageous to employ dilute alcohol in 

 extracting the resin from the lead soap, since in this case very little 

 lead salt was dissolved and the alcoholic solution needed but little 

 fractional precipitation with water in order to obtain a pure product. 



Inasmuch as it is known that alcohol dissolves the vesicating con- 

 stituent from croton oil, leaving a bland oil behind, it seemed prob- 

 able that the resin might be isolated by means of fractional precipi- 

 tation from this alcoholic solution of croton oil, and the process of 

 saponification altogether avoided. When freshly expressed croton oil 

 is shaken with rather more than twice its volume of alcohol (50 per 

 cent.), very little dissolves. After promoting subsidence by the 

 addition of kaolin or asbestos, the mixture was filtered, and the alco- 

 holic solution evaporated to dryness, when a thick oil remained. This 

 process was thrice repeated on the original croton oil. The residues 

 were dissolved in alcohol, and the solution precipitated in a number 

 of small fractions by the addition of water. The first fractions were 

 dark in colour and oily in consistence, whereas the last fractions were 

 pale yellow, and solidified to pale yellow resins which were highly 

 active. In this process of fractional precipitation, crystals separated 

 in the early stages ; these were proved to be cholesterol, which is 

 evidently present in some quantity in croton oil. A still easier 

 method of separating pure croton resin from croton oil consists in 

 extracting the oil with more dilute alcohol (25 per cent.), when the 

 resin is dissolved in a nearly pure state. The yield is, however, so 

 small that the method is not well adapted for obtaining any quantity 

 of the substance. The most t-atisfactory process for separating croton- 

 resin from croton oil which we have so far found is the following, 

 which consists in removing the resin as far as possible from the oil 

 by digesting it with alcohol, then converting the glycerides in this 

 mixture into a lead soap, from which the resin is extracted by alcohol 

 and purified by fractional precipitation with water. Croton oil is 

 warmed on the water bath for some hours with about twice its volume 



