Chemical Science. 401 



yields a very brittle substance, of a gold yellow-colour, which when 

 put into cold water produces a solution, whilst white opaque fila- 

 ments remain, which ultimately form a soft semi-transparent yellow 

 mass resembling some resins. If the aqueous solution be heated, it 

 becomes turbid, and there form, both on its surface and at its bottom, 

 yellow drops, resembling a fused resin ; these, when cold, become 

 hard and brittle. The solution re-heated, is again rendered tur- 

 bid, and this effect is produced until the whole is evaporated. 



It is found on examination, that the substance remaining undis- 

 solved by the water at first, is of the same nature as that dissolved, 

 and may itself be dissolved in abundance of water. It appears that the 

 first portion of water dissolves more than the second or third, frorai 

 the presence probably of some acid taken up by it. A yellowish- 

 brown extractive matter also appears to be present ; for the first so- 

 lution is much more coloured than the second, and the product of the. 

 second solution evaporated, appears to be much purer than that of 

 the first. If by successive evaporations the resin-like substance be 

 separated, the last, or mother liquor, contains a substance consi- 

 derably soluble in Avater, and but slightly troubled by infusion of 

 galls; the turbidnessis occasioned probably by the presence of the 

 bitter substance, a portion as is evident to the taste remaining. 



The bitter resin-like substance is slightly soluble in water ; con- 

 siderably so in alkaline solutions ; abundantly precipitated by in- 

 fusion of galls, but not at all by acetate of lead. When heated it 

 yields a white vapour, of which the taste is not bitter, and leaves a 

 very bulky charcoal. Nitric acid dissolves it, and the acid is de- 

 composed, acting upon the substance, although with difiiculty. If 

 the solution be diluted, part of the substance precipitates in very 

 bitter white flocculi. 



This substance, containing the bitterness of the colocynth, ap- 

 pears to M. Vauquelin to be a particular principle. It is very so- 

 luble in alcoh&l, less so by far in water, but giving a solution of 

 extreme bitterness and frothing on agitation. He proposes for it 

 the name o{ Coloci/ntine.—Jour. de Phar. 1824, 416. 



26. Active Principle of the Daphne Alpina. — The following con- 

 clusions have been arrived at by M. Vauquelin, in consequence of 

 experiments on this plant. 



1. That the irritating principle of the daphnds is a volatile oil. 



2. That it is during the vegetation of the plants, when they 

 contain most of the volatile oil, that they possess most energy. 



3. That this oil being gradually converted into resin, the irritat- 

 ing powers of the plant diminish in proportion. 



4. That a certain quantity of resin being formed, defends the 

 rest of the oil, from a similar change, and that it is in consequence 

 of this circumstance that old plants retain, to a certain degree, the 

 power of acting on the skin. 



