Chemistry of Essential Oils

THE CHEMISTKY OF ESSENTIAL OILS

. •12. The leaves and twigs of Abies concolor yield O03 to 0'27 per
-cent, of essential oil which has the following characters :—
Specific gravity... 0'872 to 0-878
Optical rotation - 20° „ - 28°
Refractive index 1-4760 „ 1-4778
Acid value 1 „ 1-8
Ester ,„12-5 „ 27'4
The bark of this tree yields an oil having the following characters :—
Specific gravity 0 870 to 0-877
Optical rotation - 20° „ - 21°
Refractive index 1-4809 „ 1-4833
Acid value... ... 0*87 „ 1-22
Ester „ 6'4 „ 6-9
The approximate composition of these oils is as follows:—

Furfural.

Z-a-pinene.

Z-camphene

Z-£-pinene.

Z-phellandrene

Esters as bornyaacetate

Leaf and Twig

Oil.

trace

. 12 per cent.

Bark Oil.

trace

9 per cent.

42

15

6-5

9-5

3

1

60 per cent.

Dipentene 12 to 13 per cent.

2-5 „

4-5 „

5

7

Free borneol

" Green oil"

Loss.

The remaining " pine-needle oils" may be summarised as to their

characters and constituents in the table on page 61, which includes most

of any importance which have been examined.

N. 0, GRAMINE/E.

(THE GRASS OILS.)

The principal oils of this natural order are derived from the family

formerly known as Andropogon. Much confusion had crept into the

nomenclature of these oils which has been cleared up finally by the ex-

cellent work of Dr. Otto Stapf.^1 This authority has discarded the old

names and has made the following classification, which has been uni-

versally accepted:—

Cymboppgon genus, with 10 species.

Vetiveria genus, with 1 species.

Andropogon genus, with 1 species.

The following are the salient features of these grasses as classified

by Stapf :—

1. Cymbopogon Scho&nanthus Spreng (Andropogon Schoenanthus L.).
   This is known locally as Camel grass. It is a characteristic desert
   plant able to exist on the smallest amount of water, and is distributed
   over Northern Africa and Arabia, and is also found in the Persian Pro-
   vince of Kirman where it grows at altitudes of 6000 ft. and in Afghani-
   stan, Beluchistan, and the Punjab.


2. Cymbopogon Iwarancusa Schult. This grass is believed to be the
   Nardus Indica of the Ancients. The natives call it Terankus (fever-
   healer). The plant is highly aromatic. At great altitudes it becomes
   small and narrow-leaved and then represents a transition form towards
   Cymbopogon Schoenanthus.

(^1) Kew Bulletin (1906), 8, 297.