256 POISONS : THEIR EFFECTS AND DETECTION. [§ 315. 
sulphuretted hydrogen ; the solution, after concentration, repeatedly 
extracted with ether ; and the ethereal solution saturated with dry 
C0 2 , which generally precipitates some of the alkaloids. The ethereal 
solution is then poured into clean vessels, and mixed with about half 
its volume of water, through which a current of C0 2 is passed for twenty 
minutes ; this may cause the precipitation of other alkaloids not thrown 
down by dry C0 2 . If the whole of the alkaloids are next obtained by 
these means, the solution is dehydrated by agitation with barium oxide, 
and a solution of tartaric acid in ether is added (care being taken to 
avoid excess) ; this throws down any alkaloid still present. The detec¬ 
tion of any yet remaining in the viscera is effected by mixing with 
barium hydrate and a little water, and agitating with purified amylic 
alcohol; from the alcohol the alkaloids may be subsequently extracted 
by agitation with very dilute sulphuric acid. 
Another ingenious method (also the suggestion of Selmi) is to treat 
the organic substance with alcohol, to which a little sulphuric acid has 
been added, to filter, digest with alcohol, and refilter. The filtrates are 
united, evaporated down to a smaller bulk, filtered, concentrated to a 
syrup, alkalised by barium hydrate, and, after the addition of freshly 
ignited barium oxide and some powdered glass, exhausted with dry 
ether ; the ether filtered, the filtrate digested with lead hydrate ; the 
ethereal solution filtered, evaporated to dryness, and finally again taken 
up with ether, which, this time, should leave on evaporation the alkaloid 
almost pure. 
G. D. Beal and St Elmo Brady (J . Ind. Eng. Chem., 1916) treat 
ethereal solutions of alkaloid by dry hydrochloric acid gas, drive off the 
ether, and, after weighing the residue, check the last weight by titrating 
with standard alkali, using as indicator phenolphthalein. 
§ 315. Dragendorff’s Process. —To Dragendorff we owe an elaborate 
general method of separation, since it is applicable not only to 
alkaloids, but to glucosides, and other active principles derived from 
plants. His process is essentially a combination of those already 
known, and its distinctive features are the shaking up—(1) of the 
acid fluid with the solvent, thus removing colouring-matters and 
certain non-alkaloidal principles; and (2) of the same fluid made 
alkaline. 
I. The substance, in as finely divided form as possible, is digested 
for a few hours in water acidified with sulphuric acid, at a tem¬ 
perature of 40° to 50°, and this operation is repeated two or three 
times, with filtering and pressing of the substances; later, the 
extracts are united. This treatment (if the temperature mentioned 
is not exceeded) does not decompose the majority of alkaloids or other 
active substances ; but there are a few ( e.g . solanine and colchicine) 
which would be altered by it; and, if such are suspected, maceration 
