200 THE CHEMISTEY OF ESSENTIAL OILS
Specific gravity 0'886 to 0'896
Optical rotation - 7° „ - 9° 33'
Esters 47 to 56 per cent.English oil of lavender is quite different in its odour and chemical
characters from Continental lavender oil. It is generally valued at a
very much higher rate than French oil and is esteemed more highly
than any other type of lavender oil.
The chief difference between English and French oils of lavender
lies in the fact that the former contains only about 7 to 10 per cent, of
esters calculated as linalyl acetate, whereas the latter contains up to 44
per cent, and over. Messrs. Schimmel have actively endeavoured to
establish this ester-content as the basis of the valuation of the oil.
They maintain the superiority of fine French oil over English oil, and
go so far as to say that the latter cannot compete with the former.
The author, in common with most others, holds the opposite opinion,
and considers that no comparison can be made between the two oils
on the basis of their ester-content. This is much accentuated, if such
were necessary, by the fact that linalyl acetate is not the odoriferous
ingredient of oil of lavender. It is so much modified by the presence of
other bodies, as to be regarded as only one of the odoriferous com-
pounds in the oils. Pure linalyl acetate has a marked bergamot odour,
and may be regarded as the characteristic ingredient of that oil. The
fact that English oil fetches a very much higher price than French oil
speaks for itself. For a comparison of oils grown in the same locality,
the ester comparison may, however, be of service. The oils produced
in the South of Europe are finer according as the plants are growing at
greater elevations, and according to Schimmel & Co. the very finest oils
are produced from the higher valleys of the Savoy Alps, yielding 44 per
cent, of ester. The fine oils yielding 38 to 40 per cent, of ester are
usually obtained from the Alpes Maritimes and the Basses Alpes, close
to the Italian frontier. Less fine, but still excellent, oils with 28 to 32
per cent, of ester are obtained from the French Departments of the
Gard, Dr6me, and Herault. §
These statements, however, are based only on a comparison of the
ester values, and are in direct opposition to the views and experience
of several of the leading distillers of this oil. Lautier, for example, says
(Etudes sur quelques precedes et products de parfumerie): " No one
can deny that the oils from Drome or Vaucluse are of far inferior odour
to those from the Alps. Yet the former contain 35 to 40 per cent, of
esters." It is also true that some of the oil distilled on the Italian
frontiers with 25 to 30 per cent, of esters is of the finest grade, and
Umney, who in the main agrees with Schimmel on this question, ad-
mits that with an ester value of much over 40 per cent, the oil* may be
rank. The " ester theory " has induced a considerable amount of adul-
teration with artificial esters and should be accepted only within very
definite limitations.
English lavender oil, on keeping, especially in the presence of traces
of moisture, alters considerably in character.
Brewis and Umney
l
have recorded the following figures for a series
of samples of known authenticity :—
(^1) P. and E.O.R. (1912), 5.