36 ODOROGRAPHIA. 
and 32°C. These results indicate that the cold climates of the 
North are unfavourable to the production of a very odoriferous 
oil, the high points of solidification resulting from a larger pro- 
portion of stereoptene, which is an inodorous constituent of no 
value to the consumer, but valuable to the fraudulent dealer, who 
takes advantage of its high proportion, and can thereby add a 
proportionately larger quantity of geranium oil. 
Pure otto of rose is, therefore, a mixture of a liquid oxygenated 
body to which it owes its perfume and a solid hydrocarbon or 
stereoptene which is absolutely odourless. The proportion of 
each of these constituents is certainly very variable; the Turkish 
otto may contain as much as 18 per cent., in the French and the 
English as much as 35, 42, 60, and even 68 per cent. have been 
estimated. 
The fluid constituent of otto of rose, according to Markownikoft*, 
is composed of two bodies, C,)H 0 and C,)H,,0. According to 
Poleck +, only the body C,)H,s,O is present. Investigations made 
by Eckart at the Breslau University, and published in the ‘Archives 
der Pharmacie, 1891, pp. 355-389, show that both Turkish and 
German otto contain 5 per cent. of ethyl alcohol, which can be 
distilled off below 100° C., and a body which he names Rhodinol, 
C,,H,,0, constituting the remainder or bulk of the liquid portion. 
The stereoptene is separated by dissolving the otto in 75 per cent. 
aleohol at 70°-80°, and cooling to 0° C. The alcoholic solution 
is then evaporated in a vacuum to obtain the rhodinol. The 
physical constants of this body vary, according to its source, be- 
tween the following limits :—boiling-point, 216°-217° C.; refrac- 
tive index, 1°4710-1'4725 ; refraction equivalent, 48°97—49°28 ; 
dispersion, 11*1-12°5; specific rotation, —2°7 to —2°8. The vapour 
density corresponds with the molecular weight 142°43 (C,)H,,O 
=154). Rhodinol shows all the reactions of an alcohol. Oxida- 
tion with potassium bichromate and sulphuric acid converts it 
into an aldehyde, Rhodinal, believed to be an isomer of, and 
closely resembling, citral, which can be obtained from geraniol 
by similar treatment. By phosphoric anhydride rhodinal is 
transformed into dipentene, losing one molecule of water. 
Citral, Cj)H,,O, which exists to the extent of 74 per cent. in oil 
* Bericht d. Deutsch. chem. Ges. xxiii. 1890, p. 3191. 
+ Ibid. xxiii. 1890, p, 3554. 
