Chemistry of Essential Oils

522 THE CHEMISTEY OF ESSENTIAL OILS

Both the specific gravity and saponification number are high, and these

factors, together with the figure for non-volatile matter, indicate a high

proportion of benzyl benzoate. The odour was somewhat coarse, and

the value of the oil was considered inferior to that of the finest Manila

oils, thus showing that the odour value is not proportional to the saponifi-

cation value.

Petroleum is sometimes found as an adulterant, especially of the

cheaper cananga oils. This is usually detectable by its odour, but the

following are the figures for a number of samples examined during

1915-16 by the author, which all contained petroleum :—

Specific gravity

Optical rotation

Refractive index

0-865 to 0-886

no 15°

1-4708

„

1-4885

Attempts have been made by Jahrling1 and by Gibbs to value ylang-

ylang oils in a more or less absolute manner by means of their analytical

figures. Jahrling's classification is as follows :—

Quality.

°D...

«D...

Saponification No.

Solubility.

Extra.

Below - 35°

„ 1-4900

Over 145

In 80 per cent.

Alcohol

I. (a)

Below - 48°

„ 1-4950

Over 120

In 90 per cent.

Alcohol

l.(b)

Below - 60°

„ 1-4990

Over 100

In 90 to 96 per

cent. Alcohol

II.

Over - 60°

„ 1-4990

100 or less

In 96 per cent.

Alcohol

This classification will not bear careful examination, and must only be
accepted in a very general way, the samples proving exceptions to it
being very numerous.
This oil contains a large number of aromatic compounds. The
earliest investigation of this oil was that of Gal, who showed the presence
of benzoic acid in the form of esters. Eeychler
2
has since shown that
linalol and possibly geraniol exist, together with the sesquiterpene cadi-
nene. Pinene, ^-cresol methyl ether, and a crystalline solid melting at
138°, probably a sesquiterpene alcohol, were also shown to be present.
Eugenol has been found in cananga oil, and iso-eugenol in ylang-ylang
oil. Both these bodies are probably present in the form of their methyl
ethers.
Methyl benzoate, methyl salicylate, benzyl acetate, benzyl benzoate,
and free benzyl alcohol are present in small amounts, as well as methyl
anthranilate and creosol in traces. Bacon^3 has also recently identified
formic acid, and safrol or iso-safrol.
Elze
4
has also isolated the alcohols nerol and farnesol from Java,
cananga oil, but only in very small amount.

OIL OF POPOWIA CAPEA.

This plant grows in the Ivory Coast Colony, where it is known a&

" cap6 ". It has been examined by E. G. and A. Camus, who found

1

2 Comptes Rendus,^76 (1873), 1482.

3 Bull. Soc. Chim., Hi., 11 (1894), 407, 576,1045; and 13 (1895), 140.

. Jour. Sc. 3 (1908), 65. 4 Chem. Zeit., 34 (1910), 857.