CHEMICAL HISTORY OF GENTIAN ROOT. 339 
capsule be employed, and this be inclined to expose the 
structure, it will be found to have crystallized in small 
needles. 
Gentisin is very little soluble in water at the ordinary 
temperature, the proportion is 0.020 to 100; boiling water 
dissolves but 0.026. If a small quantity of sulphuric, nitric, 
or muriatic acids be added to the water, the solvent power is 
not augmented; if, on the contrary, a small quantity of alkali 
be added, (potassa, soda, or ammonia,) the liquid immediately 
assumes a beautiful yellow colour, and the crystals are com- 
pletely dissolved, and in large quantity. 
110 of alcohol at 30°, dissolves 0.20 of gentisin at the or- 
dinary temperature; upon carrying it to ebullition, it dissolves 
1.12, and allows it to deposit in beautiful yellow crystals upon 
cooling. Alcohol at 40°, dissolves 1.60 when in a state of 
ebullition, and only 0.22 at the ordinary temperature. 
Ether, which hitherto has been regarded as its best solvent, 
does not take up at the ordinary temperature, but 0.050 to 
the 100, when it is pure. 
The alkalies dissolve it without alteration, and form with 
it crystallizable compounds, which I have been inclined to 
consider as true salts. But they are decomposed easily; and 
not having been enabled to study more than a single one, I 
have hesitated to give to gentisin the name of gentisic acid, 
which perhaps would be more appropriate. Like many co- 
louring substances, it appears truly to play the part of an acid 
as regards bases. 
I shall, nevertheless, present some of the characters of very 
beautiful yellow crystals, which I obtained by combining 
gentisin with soda. By adding some drops of caustic soda to 
distilled water holding in suspension crystals of gentisin, they 
were promptly dissolved, and gave to the water a beautiful 
yellow colour. By evaporating the liquid almost entirely, a 
crystalline mass was obtained, which, treated with boiling- 
alcohol at 30'^, was partially re-dissolved; and, upon cooling, 
was deposited under the form of beautiful long crystals of a 
golden colour. These crystals, collected and dried by expo- 
