402 
PROFESSOR WYNDHAM R. DUNS TAN AND DR, THOMAS A. HENRY 
<llmrra are due to the presence of a glucoside, which yields prussic acid under the 
influence of an enzyme also present in the plant. 
Extraction of the Glucoside (Dhurrin). 
The finely-powered plant was extracted with alcohol, the solvent distilled off and 
the residue warmed with water until nothing more dissolved. 
To this liquid aqueous lead acetate was added so long as a precipitate formed. 
The precipitate (lead tannate, &c.) was removed. The filtrate, which was now 
bright yellow, was treated with sulphuretted hydrogen, care being taken to avoid a 
large excess, and the lead sulphide was removed by filtration. A stream of air was 
then drawn through the liquid to remove hydrogen sulphide, and the solution 
evaporated in a vacuum. After several weeks the syrup deposited a small 
quantity of a crystalline substance, and more was obtained by adding small quantities 
of alcohol and dissolving the mixture of precipitated sugar and glucoside in a little 
water, and setting aside to crystallise as before. This process was very tedious, and 
the two following methods have been since found to yield the glucoside much more 
rapidly. 
A. The liquid, after the hydrogen sulphide treatment, is evaporated in a vacuum to 
a convenient volume, and the amount of free sugar determined with Fehling’s 
solution. A little more than the calculated quantity of phenylhydrazine necessary 
to convert this amount of sugar into the osazone is then added, and the mixture 
heated for 30 minutes at 100' J C., filtered, and the filtrate shaken with ether to remove 
any excess of phenylhydrazine. On evaporation in a vacuum the residue generally 
solidified to a mass of crystals, which were easily purified by recrystallisation from 
alcohol. The method always involves the loss of some of the glucoside, and cannot 
be employed in the isolation of small quantities. 
B. The second method, which is the more effective, consists in evaporating in a 
vacuum the extract left after the lead acetate and hydrogen sulphide treatment 
with sufficient purified animal charcoal to convert the whole into a powder, which is 
then exjiosed in a vacuous desiccator until quite dry, when it is extracted in a 
Soxhlet apparatus with dry acetic ether. This solvent slowly removes the glucoside, 
leaving behind nearly all dextrose and brown extractive matter. On distilling oft’ 
the solvent a syrupy residue is left, which if necessary is again treated in the same 
manner ; usually, however, it crystallises after standing in a vacuum over sulphuric 
acid for a few days. The substance may be recrystallised from hot alcohol or boiling- 
water. 
The glucoside crystallises from water in brilliant leaflets, and from alcohol in small, 
transparent, rectangular prisms. It has no definite melting point, becoming brown 
when heated much beyond 100°, decomposing completely at 200°. It is easily 
soluble in hot alcohol, hot acetic ether and boiling water, separating in crystals on 
