Chemistry of Essential Oils

236 THE CHEMISTEY OF ESSENTIAL OILS

enriched by the addition of Japanese menthol, which is usually cheaper

than American oil. Camphor oil is occasionally used as an adulterant.

The author and Bennett have found cedar-wood oil and oil of African

copaiba used as adulterants (see below). Glyceryl acetate (tri-acetin)

has been found in sophisticated oils. The behaviour on distillation as

compared with normal samples affords the surest indication of such

adulteration. The following table represents a normal distillation of

pure oil:—

PURE OIL.

(Specific Gravity, O911; Eefractive Index, 1-4645).

Quantity.

Per Cent.

12$

12$

12$

12$

12$

12$

12$

12$

Specific Gravity.

0-898

0-903

0-907

0-910

0-912

0-912

0-915

0-962

Rotation.

• 10°


• 14°


• 16°


• 20°


• 23°


• 23°


• 34°
  —

Refractive Index.

1-4660

1-4635

1-4645

1-4640

1-4615

14615

1-4630

1-4790

An oil containing tri-acetin gave the following results (Bennett):—

Fractions.

1.

2 3 4 5 6 7

Residue

•—

Quantity.

Per Cent.

12$

12$

12$

12$

12$

12$

19

Specific

Gravity.

0-900

0-902

0-910

0-920

0-926

0-938

1-147

Rotation.

• 15°


• 15°


• 14°


• 16°


• 20°


• 22°

—

I

Refractive

Index.

1-4645

1-4670

1-4650

1-4640

1-4640

1-4640

1-4640

1-4450

With cedar-wood and copaiba oils, the high boiling fractions are
found to have very high refractive indices (up to 1*4900 or even 1-500),
and in the case of African copaiba, cadinene is found in the fraction 255°
to 270°, and in the case of cedar oils, the corresponding fraction may be
laevo-rotary to the extent of - 45°.
As indicating the behaviour of African copaiba oil, which has been
used to a considerable extent for adulterating this oil, the following
figures for the pure copaiba oil are of interest. A sample of the balsam
itself was distilled by the author and Bennett and the oil collected in
four equal fractions.
The figures obtained were :—