Chemistry of Essential Oils

120 THE CHEMISTEY OF ESSENTIAL OILS

(melting-point of the nitrite 112° to 113°).t The presence of cineol was

proved by the preparation of the hydrobromide and the iodol compound.

The highest boiling fractions of the oil contain a sesquiterpene (boiling-

point 150° to 152° [17 mm.]; 263° to 265 ° [760 mm.]; dlfi0 0'928;

aD - 4° 30'), possibly caryophyllene. The high boiling portions also

contain a solid body which crystallises from alcohol in needles and

possesses the odour of Dutch myrtle.

The oil contains about 0

s

75 per cent, of paraffin hydrocarbons, of

the empirical formula C 29 H 60 melting at 63° to 64°. Free palmitic acid

was also found, as well as cineol, dipentene, and high boiling sesquiter-

penes and alcohols not yet identified.

Myrica asplenifolia, a North American plant, known as sweet fern,

yields about 0*1 per cent, of an essential oil having a specific gravity

about 0*926, which solidifies on cooling. It probably contains cinnamic

aldehyde.

SALICINE^E.

OIL OF POPLAK BUDS.

The young buds of the black poplar, Populus nigra, yield from 0

• 3
  to 0'6 per cent, of an essential oil of a pale yellow colour, with an odour
  somewhat recalling that of chamomiles. It has the following char-
  acters :—
  Specific gravity 0890 to 0907
  Optical rotation + 1° „ + 6°
  Acid value 2 „ 12
  Ester value... 8 „ 14
  „ „ (after acetylation).... 18 „ 5H
  According to Piccard,
  1
  the principal constituent is a hydrocarbon of
  the empirical formula (C 5 H 8 )«r, which from a vapour density deter-
  mination appears to be C 20 H 32.
  Fichter and Katz,
  2
  however, consider that the hydrocarbon is a
  sesquiterpene C 16 H 24 , which is probably a-caryophyllene. A small
  quantity of a mixture of paraffin hydrocarbons melting at 53° to 68° is
  also present in the oil.

URTICACE^E.

OLL OF PLLEA.

An oil distilled in Eeunion from an unnamed species of Pilea has
been examined by Schimmel & Co.^3 and found to have the following
characters:—

0*852 to

+ 33° 53' „

1-4686 „

5*1 „

24-2 „3

0*8533

+ 58° 20'

1-4690

7-7

34-4

Specific gravity ......

Optical rotation ......

Refractive index.....

Ester value.....

„ „ (after acetylation

On fractionation the oil behaved as follows : —

^Bericht, 6 (1873), 890; 7 (1874), I486. ^ Ibid., 32 (1899), 3183.

(^3) Ibid., October, 1906, 84 ; April, 1907, 113.