204 THE CHEMISTEY OF ESSENTIAL OILS
OIL OF LAVANDULA SPICA (L. Latifolia).
This oil, known as spike lavender oil, is a commercial article of con-
siderable importance, and is used very largely in cheap perfumery.
Its odour is camphoraceous, and far less pleasant than that of true
lavender oil. Lavandula spica flourishes, generally speaking, in the
same districts as Lavandula vera, and grows to a very large extent and
very freely in Spain. The yield of oil from the flowers varies from
0*5 to 1*0 per cent.
Spike lavender oil is a pale yellow or almost colourless oil having
the following characters :—
French Oil. Spanish Oil.
Specific gravity .... 0-900 to 0-921 0-903 to 0-922
Optical rotation.... - 2° „ + 7° - 5° „ + 12°
Kefractive index .... 1-4640 „ 1-4680 T4640 „ 1-4670
Ester value 3 „ 22 4 „ 27
Dalmatian spike oil resembles Spanish oil in characters.
Pure spike oil will dissolve in 2 to 2*5 volumes of 70 per cent, or in
3 to 4 volumes of 65 per cent, alcohol to a perfectly clear solution.
The most important feature of spike oil from the perfumer's point of
view, is the amount of free alcohols contained therein, which is usually
returned as borneol (calculated from the acetylation results). This
will, in genuine spike oils, rarely be less than 30 per cent. Spanish
spike oils frequently show rather less than this—28 to 29 per cent.,
but it is probable that this is due to the fact that other Labiate flowers
grow in close proximity with the lavender flowers, and are to some ex-
tent distilled with them, without any intention of fraud, but because it
is in practice impossible to separate them. Umney
l
has recorded the
analyses of about a hundred samples of spike lavender oils, with a borneol
value varying from about 23 to 41 per cent. Any sample with less than
28 per cent, should be viewed with suspicion, and samples containing
much less than this are undoubtedly adulterated.
If spike oil be fractionally distilled (preferably in a flask as illus-
trated (fig. 24), with the lowest bulb holding about 125 c.c.), using 50 c.c.
for the purpose, the first 10 per cent, obtained is usually dextro-rotatory,
and not differing more than about 2° in rotation from the original oil.
The author and Bennett have shown that (as is especially the case
with Spanish oils) pure spike oil may be slightly laevo-rotatory up to
- 3°, and also yield a laevo-rotatory fraction on distillation as above.
The following classification of spike oils grown in different districts
by Birckenstock (see under Lavender Oil) confirms this statement. So
that the statement that pure oils are always dextro-rotatory is incorrect.
Birckenstock distinguishes the following groups : Ardeche, H6rault,
Drome, Gard, Basses-Alpes, Alpes-Maritimes, and Var. Whilst, accord-
ing to the author, the first-named group represents the spike type
proper, and yields oils of the following properties: d15o 0'918 to 0'921;
aD + 7° 48' to 9° 36'; aD of the first 10 per cent, of the distillate + 8° to
- 10°; ester-content 4 to 5 per cent.; alcohol-content 21 per cenfc.;
soluble in 3 volumes 67 per cent, alcohol,—the " Var" group some-
what approaches the lavender type : dl50 0*9035 to 0'905 ; OD - 1° 10' to
0°; aD of the first 10 per cent, of the distillate + 2°; ester-content
2 to 3 per cent.; alcohol-content 20 to 32 per cent.; soluble in 5 to 6
^olumes 60 per cent, alcohol. The other groups represent intermediate
1
P. and E.O.R. (1916), 239.
