i8o PLANT AND ORGANIC CHEMISTRY 
but a system by Osse 1 has been devised to evaporate the pe¬ 
troleum-ether and save the volatile oil. 
Distillation of volatile principles may be sometimes sub¬ 
stituted by other methods, such as “infusion” and “enfleur- 
age,” of which I shall speak later. 
The following is the general plan I usually follow, based 
upon DragendorfFs scheme, in order to determine the con¬ 
stituents of any plant. Twenty, fifty, or a hundred grams of 
the dried powdered plant are weighed and macerated with suc¬ 
cessive solvents. The solvent is added in the proportion of 
ten c. c. to one gram of powder. This is allowed to stand, 
with frequent shaking, for eight days, when the liquid is re¬ 
moved with a pipette or filtered from the powder. The residual 
powder is then rinsed with more of the solvent, which, added 
to the extract first obtained, is made to a known volume. 
The powder is dried at the ordinary temperature, and is then 
ready for maceration with a second solvent, and so on, until 
the sequence of solvents has removed all soluble matter from 
the powder. The residual insoluble portions are cellulose, 
lignin, and other allied substances, which form the firm frame¬ 
work of the plant. 
The solvents used must be chemically pure. The order 
of solvents recommended by Dragendorff, and the classes 
of compounds which may be extracted by them are given in 
the table. 
PETROLEUM-ETHER EXTRACT 
Ethereal oils; volatile fat acids; glycerides; waxes; cam¬ 
phors; cholesterin or allied substances; chlorophyll and 
alkaloids with fixed oils; aldehydes; ethereal salts; alcohols; 
aromatic acids; resins. 
ETHER EXTRACT 
Resins; waxes; fats; chlorophyll; coloring-matters; organic 
acids; glucosides; alkaloids (caoutchouc, chloroform, or bisul¬ 
phide extracts). 
1 Archiv, d. Pharm. (3), vii, 104 (1875). ( Year-Book Pharm., 1876, 362.) 
