284 THE CHEMISTEY OF ESSENTIAL OILS
OIL OF BHODODENDRON.Several species of Rhododendron contain essential oils, a distillate
(from mixed species) having been examined by Haensel.
1
The yield
of oil was 0*123 per cent., which had the following characters :—
Specific gravity 0-862 at 18°
Optical rotation - 4-33°
The oil contains a small quantity of aldehydes.
Bertrand-Fils
2
have examined a specimen of this oil and found it to
have a specific gravity O840, and an ester value 63
*
5.APOCYNACE>E.OIL OF APOCYNUM ANDEOS^BMIFOLIUM.The rhizome of Apocynum androscemifolium jields about 0*016 per
cent, of essential oil having the following characters :—
Specific gravity 0-948 at 12°
Optical rotation + 0° 50'
The oil distils between 130° and 250°. It contains furfurol, and
aceto-vanillone CH 3 0 : CgH^OH). CO. CH?, which results from the
decomposition of a glucoside, named androsin.VALERIANACE/E.OIL OF VALERIAN.Oil of valerian is obtained by the distillation of the roots of Valeri-
ana officinalis, a plant growing wild, and also cultivated, in Northern
and Middle Europe and in Asia. This is the Dutch and Thuringian
root usually distilled in Europe, but a much larger yield of a very
similar oil is obtained from the Japanese plant Valeriana officinalis,
var. angustifolia.
European roots yield from 0*5 to 1 per cent, of oil, whilst the
Japanese roots yield up to 8 per cent.
The characters of the two oils are as follows :—
European. Japanese.
Specific gravity ... 0-920 to 0-960 0-965 to 1-000
Rotation
Refractive index
Acid value.
Ester „- 8° „ - 15° - 20° ,, - 35°
1-4840 „ 1-4868 1-4775 „ 1-4875
12 „ 55 1 „ 20
55 „ 100 90 „ 135
The oils from the two varieties are similar, and may be used indis-
criminately.
Pierlot investigated this oil some years ago, but his results cannot
be accepted in the light of our present knowledge of essential oils.
Oliviero^3 has carefully examined some European oils which had ab-
normally low specific gravities—*875 to '900, and isolated the terpenes
pinene, camphene, and limonene; borneol and its formic, acetic, and
iso-valerianic esters, terpineol, and probably a sesquiterpene, a sesqui-
terpene alcohol C 15 H 26 O, and a crystalline bivalent alcohol of the(^1) Chem. Zentral. (1906), «• 1495 1. * Bulletin, 4 (1920), 1.
sComptes rendus, 117 (1893), 1096.