THE ODOUR OF ROSE. 39 
is occasioned by the presence of an aldehyde, citral or geranium 
aldehyde, formed by oxidation of geraniol. This is coloured by 
the reagent at first blue-violet, after some time a turbid greenish- 
blue ; whilst the aqueous liquid assumes an intense blue-violet 
colour. Otto of rose (the liquid portion of it) consists, according 
to the investigations of Eckart *, principally of an alcohol, Rho- 
dinol, C,,H,,0, which is isomeric with, and nearly related to 
geraniol. Geraniol yields on oxidation Citral (geranium alde- 
hyde) according to Semmler +, whilst rhodinol yields, on similar 
treatment, an aldehyde Rhodinal, closely resembling citral, and this 
oxidation is partially effected when the otto is exposed to the air. 
On this logic, the aldehyde rhodinal producing the same colour 
reaction as the aldehyde citral, the fuchsin-sulphurous acid test 
can hardly be depended upon. 
The addition of ‘Indian geranium” oil to otto of rose was 
formerly made in Constantinople, but now the mixing takes place 
at the seat of the manufacture of the otto. It is stated that in 
many places the roses are sprinkled with it before being placed in 
the still; this probably makes a more perfect “blend.” Although 
the introduction of geranium oil into Bulgaria is now forbidden 
by the Government, it is still brought in secretly by Jews and 
Greeks. It is said that pure or “ Virgin” otto never leaves 
Kézanlik ; that is probably true, and the assertion that Turkish 
“Virgin” otto never arrives in England at all (even to the 
Turkish Ambassador) is almost certainly true. The manufac- 
turers avow it. The method in use in Bulgaria to detect the 
amount of adulteration with oil of geranium is very simple, and 
very defective ; it is called the congelation test, and is based on 
the fact that the addition of geranium oil lowers the temperature 
of congelation of the otto in proportion to the quantity added. 
A perfectly pure Bulgarian otto congeals at from 14° to 16° 
Réaumur (63° 5 to 68° Fahr.). If geranium is added to it, the 
same otto only congeals at 13° R. (61°2 Fahr.), 12° R. (59° Fahr.), 
11° R. (56°°7 Fahr.), and even lower according to the amount of 
“geranium” added. The purchaser takes a 20-gramme flask 
containing 15 grammes of the otto to be tested, and plunges this 
bottle into a basin of water, the temperature of which is regulated 
* Inaugural Dissertation, Breslau, 1891. 
+ Ber. Deutsch. chem. Ges. xxiii. p. 2965. 
