PREPARATION OF ESSENTIAL OILS. 75 
should here observe that it is necessary to agitate before using 
it. The following is the modus faciendi: when it is wished to 
essay cochineal or its extract, ten grains are taken, reduced 
to fine powder, and agitated with 100 grains of warm water; 
when the undissolved portions are deposited, the liquid is de- 
canted and poured into the graduated cylinder, and upon the 
residuum 100 grains more of warm water are poured; the same 
process is continued until the zero of the cylinder has been 
reached, when the cochineal will be exhausted of its coloring 
matter. The proof liquor is to be added in such proportions 
that, upon the first addition, the quantity in the tube should 
be raised to 30 or 35°, and afterwards continued until the 
liquid in the tube is clear and colorless. Then, upon examin- 
ing the height to which the mixed liquids have risen, the 
number marked indicates in hundredths the quantity of 
coloring matter contained in the cochineal submitted to ex- 
amination. This method is simple of execution, and so easy 
that it can be readily executed by an intelligent operator. 
Journ. de Chimie Med. 
ART. XVIII. — UPON THE PREPARATION OP ESSENTIAL 
OILS. By E. Soubeiran. 
Since the time that Hoffman advised the addition of salt to 
water in order to prepare the heavier essential oils,Baume alone 
has raised his voice in opposition to it, but with little effect upon 
the opinion of his successors, for all have recommended anew 
the method proposed by Hoffman; very lately, however, M. 
Mialhe has concluded, from experiment, that the employment 
of salt is unnecessary. The advantages that Hoffman attri- 
buted to the presence of salt, were the following : to render 
the water more capable of penetrating and separating the 
the vegetable substances; to prevent fermentation from taking 
