186 ODOROGRAPHIA. 
cyanic acid per 100 grammes of water, but that prepared in No- 
vember yielded 134 milligrammes per 100 grammes *. 
The oil of cherry-laurel is distilled in the south of Switzerland 
and in Italy. In England it is only obtained as a bye-product in 
the distillation of cherry-laurel water ; in this way a quantity of 
about 24 ozs., obtained during the distillation of 300 lbs. of leaves, 
was examined by Tilden in 1875, and the results of the investiga- 
tion read before the Bristol Pharmacy Assoc. in that year. Ac- 
cording to that report, the oil was found to be of a pale yellow 
colour and held in suspension a few crystals, probably consist- 
ing of benzoic acid. The sp. gr. was found to be 1:0615. It 
contained rather under 2 per cent. of prussic acid, and had an 
odour much resembling that of oil of bitter almonds. When 
shaken with excess of strong solution of acid sulphite of sodium, 
all the aldehydic constituents of the oil were dissolved, leaving 
only 1 or 2 per cent. of an oily substance containing a brown resin. 
The sulphite, when crystallized out from the solution and distilled 
with sodium carbonate, yielded an essential oil which, after drying 
by calcic chloride, presented all the characteristics of pure benzoic 
aldehyde. It distilled without residue between 174° and 178° C. 
and its sp. gr. at 17° C. was found to be 10492. ‘The small amount 
of viscid oil left by the bisulphite when distilled with potassium 
bichromate and sulphuric acid, yielded no volatile product, and the 
crystalline deposit obtained after this treatment proved, on exami- 
nation, to be benzoic acid. These experimeuts therefore indicate 
that the essential oil of cherry-laurel leaves consists mainly of ben- 
zoic aldehyde accompanied by hydrocyanic acid and about 1 per 
cent. of a volatile oil (possibly benzoic alcohol), and minute quantities 
of an odorous resin. 
It is generally understood that, like the oil of bitter almonds, 
this oil does not exist ready-formed, but is produced by the action 
of water. ‘he principles contained in the leaves, which are the 
cause of this reaction (which, as Mr. Umney, who made the investi- 
gation, points out, is instantaneous), are yet unknown and merit 
investigation. 
* Pharm. Journ. [3] xviii. p. 170. 
