182 THE CHEMISTEY OF ESSENTIAL OILS
the optical rotation steadily decreased after the first five days. The
solubility, with the exception of the first day's running, was constant
until the eighth day, after which it decreased. In order to show the
effect of prolonged boiling, a sample of oil having an optical rotation of
- 20° 40' was boiled continuously for several weeks in a glass flask with
reflux condenser, and another portion with a 10 per cent, solution of
sodium chloride. The optical rotation steadily decreased to - 13° 16'
in three and a half weeks, and the change in the brine solution was
much less, being reduced to - 16° 40' in the same length of time. It
is concluded that prolonged contact with water brings about a decided
change in the composition of sandal-wood oil and greatly reduces the
optical rotation.
East Indian sandal-wood oil is a thick, colourless or slightly yellow
liquid, of powerful aromatic odour, and having the following characters :—
Specific gravity
Optical rotation
Refractive index
Acid value
Ester „
Total alcohols (as santalol,0*973 to 0-985- 15° „ - 21°
1-5045 „ 1-5095
0 - 5 to 2 (rarely up to 6)
6 to 20
90 to 97 per cent.
These values may, of course, be slightly exceeded when the oil is not
a complete distillation. As it is very heavy and takes many days for the
wood to be exhausted on distillation, it is not uncommon to find com-
mercial specimens which in fact represent the principal fractions of the
oil, when the optical rotation may sink to about - 11°.
The oil is soluble in 6 volumes of 70 per cent, alcohol; indeed nearly
all pure samples are soluble in 5 volumes and many in 3*5 to 4 volumes.
The oil is frequently adulterated with small quantities of castor oil
and other oils. These adulterants present no difficulty when present in
appreciable amounts, but when present in small quantity are exceedingly
difficult to detect. Oils which only just satisfy the minimum require-
ments as to solubility, specific gravity, optical rotation, and santalol
value should be regarded with considerable suspicion. Glyceryl acetate
is sometimes used as an adulterant, and is detected by the high ester
value of the sample (for which see Vol. II.). Benzyl alcohol is also
sometimes used, but this will be indicated by an abnormally high
" santalol value " and also by the distillation results. With pure sandal
oil nothing distils below 280° at ordinary pressure (or 150° at 14 mm.),
whilst benzyl alcohol distils at a much lower temperature. Cedar-wood
oil is indicated by its insolubility in 70 per cent, alcohol, by its low
" santalol value," and by its high optical rotation. Further, a consider-
able distillate is obtained below 280°. The so-called West Indian sandal
oil (q.v.) is also a somewhat common adulterant, which is easily detected
by the alteration of all the constants of the oil, as well as by its de-
creased solubility and " santalol value ".
Three samples distilled in Mauritius have been examined by Schimmel
& Co.^1 Two of the samples were distilled from heartwood, the third from
sapwood. As will be seen from the subjoined table, all three were re-
markable for their high santalol-content, and their other characters also
agreed with those of East Indian oil, except that the optical rotation was
a little higher:—
(^1) Report, April, 1914, 89.