ON CYANOGENESIS IN PLANTS. 
405 
The ether soluble hydrolytic product of dhurrin is therefore undoubtedly para- 
hydroxy benzaldehyde, which melts at 118°, gives a purple colour with ferric chloride, 
and forms a colourless hydrazone melting at 178°. 
The occurrence of tribromphenol amongst the products obtained by brominating 
parahydroxybenzaldehyde has been observed by Werner (‘ Bull./ 46, 278), but it 
does not appear to have been previously noticed that, by using bromine water and 
dilute aqueous solutions of the aldehyde, the latter is converted almost exclusively 
into tribromphenol. This result was confirmed with a specimen of the aldehyde 
prepared from phenol and carefully purified from all traces of the latter. 
C 6 H 2 (OH)CHO + HoO + 4Br 2 = C 0 fLBr 3 OH + 5HBr + C0 2 . 
Dextrose. 
The acid liquid, after removal of the parahydroxybenzaldehyde, was mixed with 
powdered animal charcoal, warmed for several hours, and filtered. It was slightly 
yellow, but was sufficiently transparent for observation in a polarimeter, when it 
showed a marked dextro-rotation. It was next heated with phenylhydrazine for an 
hour on the water-bath, and the separated osazone collected and recrystallised from 
hot alcohol, when the characteristic bright yellow needles of glucosazone melting at 
204° were obtained. The sugar produced is therefore d-glucose, that is, ordinary 
dextrose. 
The Hydrolysis of Dhurrin and its Chemical Constitution. 
Hydrolysis of Dhurrin by Emulsin. —About 1 gramme of the glucoside was 
dissolved in cold water, and a filtered extract of sweet almonds added, the mixture 
being then set aside for 12 hours at the ordinary temperature. After a few minutes 
the odour of hydrocyanic acid was perceptible, and at the end of the experiment 
over 90 per cent, of the possible quantity of parabydroxybenzaldehyde was obtained. 
This method of hydrolysing the glucoside is to be preferred to that involving the use 
of acids, since the aldehyde produced is more easily purified. 
The quantitative determination of the acid hydrolytic products of dhurrin 
appeared to afford a method of confirming the formula assigned to this glucoside 
from the results of combustion, which are perhaps not completely satisfactory owing 
to the difficulty of obtaining the substance anhydrous without decomposing it. 
Attempts were therefore made to determine the amounts of hydrocyanic acid and 
dextrose produced on hydrolysis. For this purpose a weighed quantity of dhurrin 
dissolved in water was placed in a small Jena flask, and sufficient dilute (10 per 
cent.) hydrochloric acid added. 
The flask was then corked and secured by wire and heated in a water-bath for 
5 minutes. In this way complete hydrolysis is secured without much secondary 
decomposition. The prussic acid formed was distilled off in a gentle current of steam, 
