254 THE CHEM1STKY OF ESSENTIAL OILS
Lehmannl has drawn attention to the fact that oils of recent distilla-
tion have frequently had a lower specific gravity and optical rotation than
usual, and also showed a marked decrease of solubility in 90 per cent,
alcohol. The amount of oil obtainable from the herb is also decidedly
smaller, seldom being above 2 per cent. Two of the typically abnormal
oils showed the following constants:—
Specific gravity.0-935 to 0'937
Optical rotation - 9° „ - 34°
Refractive index 15050 „ 1-5070
Saponification value 4-5 „ 6-5
,, „ (after acetylation)... 38 „ 42
Both were soluble in 4 to 5 volumes of 90 per cent, alcohol. The
odour of the oil was especially fine and strong. The suspicion that the
leaves had been adulterated proved to be unfounded. The marked re-
duction in the yield of the oil and the change in the nature of the con-
stants is probably attributable to atmospheric conditions existing during
the time of the growth of the herb.
Patchouli oil is adulterated to a certain extent with the oil from other
leaves which are fraudulently packed with patchouli leaves, such as basil
leaves and the leaves of a Malayan plant, known as " purpulut " (Urena
lobatd). The leaves of Hyptis suaveolens are also used as an adulterant.
Sassafras (or heavy camphor oil) is sometimes found as an adulterant,
as well as cubeb oil, cedar-wood oil, and—rarely—petroleum.
The earliest chemical examination of this oil was made by Dr. Glad-
stone in 1864, who stated that it contained a hydrocarbon analogous to
that from oil of cubebs, together with a small quantity of an intensely
blue colouring matter which he termed cserulein. Gal
2
and Mont-
golfier^3 have shown that the oil contains a solid body, which they
termed patchouli camphor, and which Wallach has shown to be a ses-
quiterpene alcohol C 15 H 26 O. This body is probably the oxidation pro-
duct of other substances in the oil, and appears to have little or no
odoriferous value. It is deposited when the oil stands for long in a
cold place. When recrystallised it melts at 56°. It is laevo-rotary,
the specific rotation in the melted condition being - 118°, or in chloro-
form solution - 97° 42'. Dehydration gives rise to a hydrocarbon
G15H24 patchoulene. This hydrocarbon has an odour of cedar-wood
oil, boils at 254° to 256°, and has a specific gravity 0*9334 and optical
rotation - 36° 52'.
Wallach claimed to have isolated cadinene from the oil, but later
researches have shown that this sesquiterpene is absent from the oil,
so that the oil examined by Wallach was probably adulterated.
Von Soden and Eojahn
4
have examined samples of patchouli oil of
known purity, and have separated it into two main fractions by distilla-
tion under reduced pressure. The earlier fractions of specific gravity
0*984 to 1
- 002 were found to consist chiefly of patchouli alcohol, whilst
two other fractions of specific gravity 0946 and 0964 were found to
consist of high-boiling sesquiterpenes. A series of refractionations suc-
ceeded in separating a fraction of specific gravity 0930 to 0940 and of
optical rotation — 50°, and one of the same specific gravity but of rather
higher boiling-point. From the former, after hydrolysis, a sesquiterpene
was obtained in a state of purity which boiled at 264° to 265° at 750 mm.,
' Chem. Zeit. (1913), 37, 1589.^2 Comptes rendus, 68 (1869), 406.
* Ibid., 84 (1877), 88. * Bericlite, 37 (1904), 3353.
