150 
Selected Articles, 
ART. XXXIV. — ON AN ACID FROM SAPONINE. By E. Fremy, 
Ojv the 17th of February the author addressed a note to 
the Royal Academy of Sciences, on Esculic acid. When 
pulverized horse chestnuts are treated with cold alcohol, this 
menstruum takes up the acrid principle they contain, and on 
evaporation affords a gelatinous mass, of a light yellow co- 
lour, which has the following properties: It is soluble in wa- 
ter and alcohol in all proportions, but its solubility decreases 
in proportion to the augmentation of the concentration of the 
alcohol; it is insoluble in ether. The aqueous solution froths 
on agitation ; when treated with nitric acid it is transformed 
into a yellow resin. It is seen that these properties are the 
same as those of the saponine obtained from the Egyptian 
soapwort. It may, therefore, be asserted that horse chest- 
nuts also contain saponine. 
If this saponine be treated with hydrochloric acid, a pre^ 
cipitate is not immediately formed, but the fluid soon becomes 
turbid, and deposits an acid, white substance; if heat be used 
this precipitation takes place at once. This precipitate is 
scarcely soluble in cold water, very soluble in alcohol, and 
crystallizes in small granular forms. The author has given 
it the name of Esculic acid. Besides this acid, the saponine 
in question contains a very acrid colouring principle which 
has acid properties. The combination of this substance with 
potash is insoluble in weak alcohol, whilst the esculate of 
ihis alkali is very soluble in that fluid. 
Saponine, therefore, is to be treated, either with the aid of 
lieat, or otherwise, with a little potash ; then alcohol is to be 
added, which precipitates the combination of the colouring 
fnatter with the potash, in the form of a thick syrup. The 
supernatant fluid is to be decanted and evaporated, to drive 
off the alcohol. It is then to be treated with an acid, which 
(precipitates the esculic acid. It is therefore evident, that in 
the saponine of the horse chestnut, this acid is retained by this 
yellow colouring matter, which prevents its precipitation. Pure 
esculic acid is almost insipid, and scarcely soluble in water, 
