516 THE CHEMISTEY OF ESSENTIAL OILS
prefer to nickelplate it. The oil is very sensitive towards air and light,
and must therefore be kept in a dark place and in well-filled vessels.
Experiments with steam distillation in vacuo should be made with proper
apparatus, and the blossoms should also be macerated beforehand; this
would no doubt favour a rapid production of oil.
- " The valuation of ylang-ylang oil by means of an analytical deter-
mination of the individual constituents is a matter of considerable diffi-
culty and doubt, as it owes its perfume to a large number of odoriferous
substances, and, as a matter of fact, the oil is judged in the trade chiefly
by the odour so long as analysis shows that it is pure."
The ylang-ylang tree was introduced into Eeunion about 1770, but it
was not exploited as a source of perfume material until about 1880.
According to Desruisseaux,^1 the plant succeeds well in the island in all
porous and substantial soils which are met with in the tropical and
equatorial zones. It dreads above all the presence of stagnant water, as
also violent winds, which in some countries blow almost incessantly.
Consequently in Eeunion, below the 21st degree of South latitude, it has
been recognised that at an altitude of 400 metres and upwards, the ylang-
ylang did not flourish. But it is certain that in the equatorial zone the
tree may accommodate itself to higher altitudes and flourish there.
The ylang-ylang in Eeunion begins to produce flowers at the age of
eighteen months to two years. At the age of four years, a tree may yield
5 kilos of flowers if it is planted in a rich soil. Trees have been known
of ten years of age to produce, under the action of strong manuring, as
much as 10 and 15 kilos of flowers annually.
The flowers succeed each other on the tree continuously, so that it is
possible, so to speak, to pluck them all the year round. But it is during
the winter season that they are particularly plentiful, that is from Nov-
ember to March in the tropical countries of the Southern hemisphere.
The flowers do not all develop at the same time on the bunches ; only
those which are at the right stage should be plucked, with a portion of
their peduncle. For this purpose the gatherer should make use of his
nails or of a pair of small scissors. The flowers are placed in small
baskets or cloths.
When plucking is in progress, it is necessary to avoid shaking the
branches of the tree and the bunches of flowers too roughly, so as not to
spoil those which remain on the tree, and when the latter is too high, the
gatherers should not climb on the branches which break rather easily,
but should use a double ladder. Generally this delicate work is performed
by the women and children.
The flower should be delivered to the stills a short time after gather-
ing, otherwise its yield of essential oil will decrease and the fineness of
the perfume will be lost. The plucking should be made as far as possible
in the early morning, and it is necessary to avoid bruising the flowers.
Bruised, faded, and blackened flowers yield an essential oil of inferior
quality.
The distillation is carried out in presence of water, and may be per-
formed in a simple still. The type of still which provides for the return
of the waste waters of distillation is the most practical.
The flowers of ylang-ylang contain from 1
- 5 to 2'5 per cent, of their
weight of essential oil. They are richer when they are derived from lands
well exposed to the sun and not very moist, and when the plucking is
1
Bulletin du Jardin Colonial (1910).
