174 
PHARMACEUTICAL EXTRACTS. 
success in fixing the Daguerreotype images, and for many 
other purposes. 
The red chloride of gold (terchloride) is prepared in the 
same manner; only the aqua regia employed is made with 
two parts of hydrochloric acid, and one part of nitric acid. 
The gold is first treated with excess of aqua regia, on a 
sand-hath, and the water-bath is not employed until the 
metal is entirely dissolved. In other respects the operation 
is conducted in the same way as in the preparation of the 
yellow chloride. 
Ibid, from Ibid. 
ART. XLII.—ON THE PREPARATION OF PHARMACEU- 
TICAL EXTRACTS. 
BY M. BURIN. 
In a work which I hope soon to publish, I have treated 
of the preparation of extracts in a series of articles, which, 
considered collectively, are founded on the following prin- 
ciples: — 
1st. A vegetable substance being given, to endeavor to 
ascertain to which of its chemical constituents its medicinal 
activity should be ascribed. 
2d. The active constituents being known, to study their 
chemical characters, in order to determine, among other 
things, the solvents which ought to be employed for sepa- 
rating these from such as are inert, and which on that ac- 
count may prevent the preservation of the product, or de- 
stroy the energy of its properties. 
3d. To effect the evaporation of the liquid employed as a 
vehicle, in such a way as to avoid completely the decom- 
