208 THE CHEMISTEY OF ESSENTIAL OILS
[Very many samples of Spanish " rosemary" oil have figures well
outside the above limits. They are usually, however, distillates fron*
a mixture of sage with rosemary flowers—and are accepted as " com-
mercial " Spanish rosemary oil.]Tunisian Rosemary Oil.Specific gravity 0'905 to 0-925
Optical rotation - 2
°
„ + 6°
Befractive index 1-4660 „ 1-4695
Acid value 1 „ 2
Ester , 5 „ 10
Total alcohols 12 to 17 per cent.The solubility is identical with that of French oil.English Rosemary Oil.Specific gravity 0-8965 to 0*924
Optical rotation - 10° „ + 3°
Be ractive index 1-4650 „ 1-4690
Esters .. about 5 per cent.Greek rosemary oil does not differ materially from Dalmatian or
Spanish rosemary oils; but Corsican and Sardinian oil have the peculi-
arities of having a high optical rotation (up to + 18°), high ester value
(about 10 to 13 per cent.), and a high percentage of alcohols (up to-
25 per cent.).
Up till recently laevo-rotatory rosemary oils, or oils yielding a laevo-
rotatory first 10 per cent, on distillation, were regarded as adulterated.
The above figures indicate the incorrectness of this view. The whole
question of the fractional distillation of this oil has been studied by the
author and C. T. Bennett,^1 who had consigned to them authentic speci-
mens of rosemary herb grown in Spain and France respectively (some
300 Ib. in all), and the oil from these was distilled in the laboratories,
of Wright, Layman & Umney, Ltd., under the direct supervision of
Mr. J. C. Umney. The results of the examination of these oils prove
beyond doubt that a laevo-rotatory oil is consistent with purity, and
also a dextro-rotatory oil giving laevo-rotatory fractions.
It is customary in France to distil the oil from herb which has been
collected after the flowering period (February and March) and dried for
about eight days in the sun. In Spain the distillation goes on all the
year round, and some variation is therefore to be expected. Both fresh
and dried herbs are employed, the latter when the supply is greater
than the capacity of the stills and when it has to be carted from a long
distance. In the dry state the leaves can be readi'y separated from the
stalks by threshing, but in the fresh condition it is impossible so to-
separate them. The yield from the fresh herb is from 0
- 4 to 0
75 per
cent, while the dried leaves yield about 1 per cent, of oil, which is of
finer quality than that from the fresh herb. The characters of three;
typical samples were as follows :—
(^1) Chemist and Druggist (1906), 137.