ANONACEJE 521
Umneyl gives the following figures for ylang-ylang oils, which are
*not intended to be exhaustive, but represent some oils examined, showing
the percentage of non-volatile matter when the oil (about 2 or 3 grams)
is heated on the water-bath for two hours:—Specific Gravity (15°)
Optical Rotation
Refractive Index (20°)
Ester Number.
Non-volatileManila.•927 to -969
-38° „ -51°
1-494 „ 1-505
99-6 „ 153-2
4-3 to 16-4 °/ 0Bourbon.•964 to -967
-39° „ -41°
1-5130
142-6 to 160-1
25-1 to 40-3 °/ 0Madagascar.•961 to -981
-30° „ -42°
1-5122
123-2 to 171-2
16-9 to 29-3
°
/ 0Mayotte.•947
-48°
1-5070
114-7
14-0 to 19 °/ 0It is doubtful whether these high non-volatile residues are due to
natural constituents of the oil, or to added substances, such as benzyl
benzoate. If the oil be heated at 110° to 120° until no loss in weight
•occurs, any residue above 5 to 7 per cent, should be regarded with sus-
picion and carefully examined. The saponification value of the non-vola-
tile residues (at this temperature) for normal oils is usually from 65 to 100.
If much fatty oil is present as an adulterant, this figure will be greatly
increased, and the residue should be examined for fatty acids, which
•can be separated from the saponification liquid, and the molecular
^weight determined by titration with alkali, when an indication of the
nature of the acids is obtained.
Umney finds that in the case of the finest Manila oils the residue
obtained by evaporation does not usually exceed 6 per cent., whilst
inferior oils frequently contain much more non-volatile matter. It should
be noted that the loss by evaporation on a water-bath is not constant
even after six hours, and that if a larger quantity of oil than 1 to 2 grams
be taken the rate of volatilisation is much slower.
Benzyl benzoate, one of the natural constituents of this oil, is very
slowly volatilised when heated on a water-bath, as shown by the follow-
ing experiment: 5 grams of pure benzyl benzoate heated in a flat bronze
'dish over a water-bath showed the following loss:—
After 3 hours the loss was 9*3 per cent.
6
. 9
, 12
. 15 „
, 18
, 21
45-4 „
59-3 „
72-3
85-7
98-3
It would appear, therefore, that the presence of benzyl benzoate in
^considerable quantity in ylang-ylang oil would be shown by heating the
oil on a water-bath for a limited time. This ester, which has a high
saponification value, is comparatively inodorous, and, as it might be
employed as an adulterant, the usual tests for ylang-ylang oil should be
•supplemented by a determination of the non-volatile matter to guard
against such sophistication.
A sample of pure ylang-ylang oil distilled in Mauritius had the follow-
ing characters:—
Specific gravity 0-9J3
Optical rotation
Refractive index (25°)
Saponification number
Non-volatile residue
- 28°
1-5072
180
16-6 per cent.(^1) P. andE.O.R. (1914), 37, 85.