214 
BRITISH PHARMACEUTICAL CONFERENCE. 
Pure Arsenic resublimed.6 08 
Pure Distilled Mercury.14*82 
Iodine resublimed.49‘ 
Alcohol, 1 drm. or q. s. 
Water.8 oz. 
The arsenic should be in the finest possible condition; the more minute, the 
more rapid the combination with the iodine. This combination should be 
first made with the arsenic by the addition of a little water, sufficient of the 
iodine being used for a perfect union ; this should be carefully dried, and the 
remainder of the process completed by the entire and effective combination of 
the iodine remaining, together with the mercury, the iodide of arsenic, and as 
much of the alcohol as may be required. The proportion of water being added 
to make up eight ounces, there should result a solution of a permanent charac¬ 
ter, both physically and chemically. Dr. Donovan found that when the tri¬ 
turation of the ingredients was continued until the alcohol became as thick 
as treacle, he obtained the most effective and complete solution. This may 
be left to the operator, provided it be borne in mind that there should be no 
residue whatever. The process of Dr. Donovan may be advised for 
adoption, with these precautions, until the framers of any future Pharma¬ 
copoeia see fit to authorize the 1 recommendation of any other. 
ON THE DETECTION OF FIXED OILS IN PLANTS. 
BY THOMAS T. P. BRUCE WARREN, F.E.S. 
The process here recommended is admirably adapted for detecting, on a 
small scale, the existence of fixed oils in vegetable substances. 
It consists in treating the recent emulsion obtained by expressing the 
juices from the plant, first with hydrochloric acid, which precipitates caout¬ 
chouc if present, and destroys the emulsive character of the juice. The 
caoutchouc collects as a white tenacious mass on the surface of the liquid, 
which is to be completely removed. 
The residue is strongly agitated with bisulphuret of carbon, and, after 
digesting for some time, the supernatant part is decanted off. 
The bisulphuret of carbon will be found to have dissolved the fatty matter 
contained in the juice, which may be recognized by adding a few drops of 
dichloride of sulphur. A granular precipitation immediately follows on the 
addition of the dichloride of sulphur, which is not redissolved either in ether, 
chloroform, or bisulphuret of carbon, even when assisted by heat.* 
The hydrochloric acid should be added in tolerably large quantity, to en¬ 
sure the agglutination of the caoutchouc, since it does not interfere in the 
least with the subsequent part of the test. 
In dealing wfith woody or hard fibrous substances, the same in coarse 
powder may be simply digested in bisulphuret of carbon, and afterwards in 
the manner above indicated.f 
* These precipitates may, in some instances, be regarded as presenting individual cha¬ 
racteristics, and thus offer a means of detecting admixtures of oils. 
f It will be better, in some cases, to treat such substances with highly rectified and 
washed ether, and to precipitate the caoutchouc by the addition of a small quantity of 
alcohol. 
