Chemistry of Essential Oils

LABIATE 207

tke Alpes-Maritimes remain uncultivated; in the region of Draguinan
and Lorgues vast tracts of the Basses-Alpes put enormous quantities of
fragrant rosemary at the disposal of the distiller, but the cost of the pro-
duct would barely repay the expense of labour and fuel.
The average yield of essential oil is from 1 to 1*8 per cent.
Eosemary oil has been examined by several chemists. Bruylants
l
claimed to have isolated a terpene from the oil, but as the oil on which
he worked had a specific gravity 0'885, it was probably adulterated with
turpentine, so that his results cannot be accepted with confidence.
Gildemeister and Stephan^2 have, however, isolated pinene from the
lowest boiling fractions of the oil, which is probably a mixture of dextro-
and laevo-a-prnQue. Camphene has also been definitely identified as a
4X>nstituent of the oil. These two terpenes have been identified, not only
in French, but also in Dalmatian oil. Weber
3
has isolated cineol, and
has also prepared dipentene dihydrochloride from a terpene fraction of
the oil, which makes it probable that dipentene is also present. Cam-
phor 4 and borneol^5 are important constituents to which the oil owes
much of its odour. Traces of esters, probably of borneol, are also
present.
Pure rosemary oil has the following characters:—

French Oil of Rosemary.
Specific gravity
Optical rotation
„ „ (of 1st 10 per cent, distilled)
Refractive index
Acid value.
Ester „.
Biters per cent
Total alcohols (as borneol).

0-900 to 0-920

• 4° to + 13° (rarely to - 9
  C
  )


• 6° „ + 14° ( „ „ - 18°)
  1-4660 to 1-47*5
  0-5 ., 2
  3 „ 14
  1 „ 5
  8 „ 19 per cent.
  The oil is usually soluble, with at most faint turbidity, in from 1 to
  10 volumes of 80 per cent, alcohol.
  Dalmatian Rosemary Oil.
  Specific gravity
  Optical rotation
  „ ,, (of 1st 10 per cent, distilled)
  Refractive index.
  Acid value.
  Eater
  Esters per cent.
  Total alcohols

0-894 to 0-914

• 1° to + 7° (rarely to + 12°)
  
  
  • 1
    1-4650
    0-5
    5
    1-8
    8
  
  
  
  

to + 8°

„ 1-4700

5 1-5

520

, 7 per cent.

„ 18 „

The solubility is identical with that of French oil.

Spanish Rosemary Oil.

Specific gravity 0-898 to 0-922

Optical rotation - 6° „ + 12°

„ „ (of 1st 10 per cent, distilled) - 6° to f 6° (rarely a little higher)

Refractive index 1-4660 to 1-4700

Acid value 1 „ 2

Ester„ 2-3 „ 17-5

Esters per cent. 0'8 „ 6 per cent.

Total alcohols 10 „ 20 „

. The solubility is identical with that of French oil.
l
Jour. de Pharm. etde Ghim., iv. 29 (1879), 508.
Arch der Pharm., 235 (1897), 586. * Annalen, 238 (1887), 89.
8 Ibid., 114 (1860), 197.
Jour, de Pharm. etde Chim., iv., 29 (1879), 508.