338 
SELECTED ARTICLES. 
crystalline substance, and hardly acts upon the fatty substance. 
If the gentisin, when crystallized by cooling and spontaneous 
evaporation, still contains a little oil, which may have been 
retained from the ebullition, it can be removed by a little 
ether. If it be re-dissolved in boiling alcohol at 30°, it is 
obtained under the form of perfectly pure and beautiful yellow 
crystals. 
Whatever method I might employ, I have never obtained 
more than one part in a thousand, as the product. 
Gentisin is of a pale yellow colour, crystallizes well in long 
needles, is extremely light, has a feeble, peculiar odour, and 
no taste; it possesses no action upon the economy; several 
grammes may be taken with impunity. When exposed to 
the air, gentisin undergoes no alteration; heated to 100 R. in 
a salt water bath, it does not lose weight, and undergoes no 
change.* Placed in a tube plunged in oil heated to 250°,t it 
is not decomposed. At a temperature approximating 300°, 
it assumes a light brownish tint, but still is not volatilized. 
But by heating it by means of a spirit lamp, this substance 
gives off some yellow fumes, which are condensed in the cold 
portion of the vessel. By continuing to heat it, it becomes 
more and more deeply coloured; is diminished in bulk and 
enters into fusion, assuming the appearance of a fatty sub- 
stance. If the heat be not pushed too far, the gentisin, in part 
decomposed, and having the appearance mentioned, becomes 
concrete upon cooling. It then takes the appearance of a 
brown mass, with a crystalline structure; if a small porcelain 
* It is stated, in the number for July of the Repertoire de Chemie et 
de Physique, p. 110, in a note by M. TrommsdorfF upon gentianin, that 
" heated in a glass tube to the temperature of boiling water, a small 
quantity is decomposed, and the remainder sublimes under the form of 
yellow needles." This is, doubtless, by mistake, as MM. Henry & Ca- 
ventou did not announce it in their memoir, and as gentianin is far from 
being decomposed at this temperature. 
f M. Fee, in his Cours d'Histoire Naturelle Pharmaceutique,also tells 
us that gentianin is decomposed at 135°, and yields as a product an azoted 
matter. This, moreover, is not mentioned in the memoir of MM. Henry & 
Caventou. 
