224 THE CHEMISTEY OF ESSENTIAL OILS
water containing the oil passes through a bamboo reed, L, inserted in K
to the florentine flasks, O. Each of these consists of a little wooden
container in which a glass cylinder (an old bottle without bottom or neck)
is inserted. In this, the water separated from the oil runs through the
little pipe, P, again into the boilers, A, H, I. As soon as the water in
C becomes hot, the workman replaces it with cold water. The empty-
ing is effected by a bamboo syphon. The workman inserts the short
arm in the inverted cooler, closes the lo'wer opening and sucks the syphon
until the water flows into it. According to the inborn easy-going nature
of the Jap workman, who likes to pause in his work for a smoke, it
often happens that the cooling water in C begins to boil and steam runs-
through instead of the condensed water saturated with oil, so that the
atmosphere in the neighbourhood becomes so impregnated with pepper-
mint that anyone near loses sight and sense of smell. The workman
does not go unpunished, as he burns his mouth by sucking up the boil*
ing water; that, however, does not prevent him from going on smoking,
and the same thing happens again. In addition to the direct loss of oil
caused by this negligence, it often happens that the water-boiler be-
comes dry, and then the herb in the still is burnt, in spite of the straw.
This sometimes happens in spite of all precautions, as the flames fre-
quently overheat the boilers if the water runs too low, and the products
of burning straw get over with the distillate, which explains why Japanese
peppermint oil sometimes has a peculiar empyreumatic flavour.
Japanese oil of peppermint contains a very high proportion of
menthol, a large amount of which is frequently removed, and the de-
mentholised oil sold as such. The term Japanese peppermint oil is
understood on the market as meaning the dementholised oil. The usual
manner in which the menthol is obtained is by a simple process of freez-
ing, whereby the crystals separate, and are freed from the adherent oil
either by pressure or centrifugal treatment. To purify them they should
be recrystallised from a suitable solvent, such as alcohol. If it is wished
to extract the maximum quantity of menthol, it is advisable to distil off
the terpenes, etc., under reduced pressure, and then freeze the residual
oil.
The crude distillate, containing the whole of the menthol, is known,
in Japan as Torioroschi.
Japanese peppermint oil was first carefully investigated by Beckett
and Wright.^1 They found present in the oil besides menthol, a body iso-
meric with menthone but which was not identified as menthone. Other
bodies found by these chemists were almost certainly mixtures and not
chemical individuals.
Murayama^2 detected Z-limonene in the oil, and Schimmel & Co.^3
isolated from it the alcohol ethyl-amyl carbinol C 2 H 5. CH(OH)C 6 Hllr.
and
4
also the ketone A'-menthenone.
The identity of the ethyl-amyl carbinol found in the oil has been
settled by the preparation of the same body synthetically. Schimmel
& Co.
5
heated normal caproic aldehyde with magnesium methyl-iodide,
and thus obtained ^-ethyl-w-amyl carbinol, which was found to possess
characters substantially identical with those of the natural compound.
(^1) Jour. Chem. Soc. (1876), 13. 2 Jour. de Pharm. et Chim., vii. 1 (1910), 549
^Report, 5 April, 1912, 103. Ibid., October, 1910, 97.
, April, 1913, 82.