Chemistry of Essential Oils

N. O. GEAMINE^E 65

The trade in citronella oil is in a very unsatisfactory condition, as
practically all the oil exported from Ceylon is, by consent, adulterated,
the amount of pure oil sold being almost negligible. This aspect of the
question will be discussed latter.
A pure distillate should have the following characters :—

Specific gravity

Optical rotation

Refractive index

= 0-898 to 0-920

= _ 7° to - 18° (rarely to - 20

°

)

= 1-4785 to 1-4900

FIG. 10.—Citronella oil still. 1 chimney; 2 steam boiler; 3 still; 4 and 5 con-

denser ; 6 underground cellar; 9 receiver.

The total acetylisable constituents, calculated as geraniol should not

fall below 55 per cent., and is often above 57 per cent., rarely reaching

60 per cent. The oil should dissolve to a clear solution in 1 to 2

volumes of 80 per cent, alcohol, and on the addition of more alcohol up

to 10 volumes, no turbidity—or at most a slight opalescence—should be

produced. The principal adulterant of this oil is petroleum, but resin

spirit has also been used, and during the past few years the lighter frac-

tions of petroleum of the petrol type have been employed. The author

and Bennett have examined the effect of adulteration on the characters;

of the first 10 per cent, distilled from the oil, with the results set out*in

the following tables :—

TABLE I.—PURE CITRONELLA OILS.

Characters of first 10 per cent, distilled at 20 to 40 mm. pressure.

Specific

Gcavity

at 15-5°.

A 0-861

B

C

D

E

1

. 0-861

. 0-860

. 0-P63

. 0-866

. 0-867

Rotation in

100 mm.

Tube.

• 44°


• 43°


• 35°


• 23°


• 6
  °


• 11°

Refractive

Index at

190 C.

1-4680

1-4732

1-4692

1-4655

1-4590

1-4571

1

E is an oil from the Straits Settlements.

(^2) F is a Ceylon oil distilled by Winter, and probably prepared by fractionation.
VOL. I. 5