366 M.PelletieronCafein, [Nov. 



cafein, and then evaporate all the liquors to obtdin a dry 

 extract, using a salt-water bath towards the end of the evapora- 

 tion ; 1 then treat the extract with alcohol of sp. gr. 817 ; this 

 dissolves the cafein without taking up any sensible quantity of 

 the saccharine and gummy colouring matter. In order to extract 

 the whole of the cafein, the extract must be treated five or six 

 times with alcohol, taking care to dry it by steam, or a salt- 

 water bath, before each addition of fresn alcohol. 



The spirituous solutions filtered through purified animal 

 charcoal are to be concentrated by distillation to a certain point, 

 and then very fii e crystals of cafein are obtained. 



Having procured by this process a very considerable quantity 

 of cafein, even from some much damaged coffee which my col- 

 league, M. Henry, had sent me, I had an opportunity of deter- 

 mining whether cafein saturated acids, and whether, as I at first 

 thought, it ought to be regarded as a salifiable organic base. I 

 was soon convinced that this substance possessed no electro- 

 chemical property. Acids increase its solubility but little in 

 cold water, in which it is but slightly soluble, but by hot w^ater 

 it is readily taken up. The circumstance which led me into an 

 error was this ; I obtained some crystals, in the form of long 

 transparent prisms from the acid liquors, whilst from pure water 

 I procured only a confused crystallization of opaque silky 

 threads ; whether acid be present or not, weak solutions give 

 long, acicular, transparent, and slightly fiexible crystals ; but 

 whatever quantity of acid and cafein be mixed, the acidity of the 

 liquor depends upon the relative proportions of water and acid, 

 and it is not sensibly diminished by the cafein. 



I shall not now state the other properties of cafein, referring 

 for them to the Dictionnaires de Technologic et de Medicine, 

 already mentioned, I have only noticed the action of acids to 

 correct an error which I had committed. 



Returning to the process for extracting cafein, it may be 

 inquired, why, as this substance is not alkaline, magnesia is 

 employed to obtain it? The magnesia appears to me to favour 

 the operation on account of its affinity for colouring matter. 

 Having several times endeavoured to do without it, 1 have indeed 

 obtained cafein, but in much smaller quantity, and as it was very 

 impure, much of it was lost by purifying it. I have no doubt, 

 but that by employing acetate of lead, or any other substance, 

 which would separate the colouring matter, the same results 

 would be obtained ; but the process which 1 have detailed 

 appears to me to be more simple than those which it would be 

 necessary to follow in making use of metallic salts. 



According to the analysis which M. Dumas and I have made 

 of cafein, it is of all vegetable products that which contains 



