EUTACB^L. 425ventage of terpenes and sesquiterpenes in the original oil is calculated.
For purposes of further identification the rotation is estimated, and, if
necessary, the characteristic derivatives are prepared. The terpenes,
of which the principal constituent is d-limon§ne, are characterised by a
pronounced dextro-rotation ; they yield a liberal proportion of limonene
tetrabromide, whereas the sesquiterpenes, which consist chiefly of
bisabolene, are laevo-rotatory and may be identified from the bisabolene
4 rihydrochloride.
OIL OF ORANGE.
There are two varieties of ordinary orange oil in commerce, almost
identical in composition and properties, but with odours and flavours
somewhat different. These are the sweet and bitter orange oils, ob-
tained in the same manner as oil of lemon, from the peel of Citrus
aurantium subsp. sinensis and Citrus aurantium subsp. amara respec-
tively. With regard to the origin of the trees, Prof. Sadebeck (Plant
Cultivation in the German Colonies, and their Products) says : " The
orange tree is probably indigenous to South-eastern Asia, and thence
has spread to the Sunda Islands, further India, Persia, Arabia, Syria,
North Africa, and Southern Europe. Towards the end of the ninth
century of the Christian era, it appeared in Arabia, and since A.D. 1002
in Sicily." An oil is prepared by distillation, but it is much inferior in
every respect to the expressed oil. Considerable parcels of West Indian
oil have been placed on the London market, the examination of which
shows this to be equal if not superior to Sicilian oil.
According to Umney l the chief centres of cultivation in the Medi-
terranean littoral are Hyeres, Cannes, Grasse, Nice, Mentone, Bordi-
ghera, San Eemo, Savone, and Nervi, near Genoa. In Algeria there are
many districts where orange trees flourish. Perhaps the most beautiful
plantations of Europe are the orange groves of Milis in Sardinia, those
of Soller in the island of Majorca, the gardens of Sorrente, near Naples,
the Messina plantations near the foot of Mount Etna, and those of
Eeggio in Calabria.
The sweet orange is largely cultivated in the West Indies and in the
Southern States of North America. In Florida it grows wild in great
abundance and is also exclusively cultivated for its fruit.
The bitter or Seville orange is known as Citrus bigaradia (Duhamel),
Citrus aurantium var. amara (Linnaeus), and Citrus vulgaris (Eisso), of
which some twelve varieties are known. The sweet or Portugal orange
is known as Citrus aurantium (Eisso), of which no fewer than nineteen
varieties are known.
Orange trees require plenty of air and light to enable them to resist
the attacks of parasitic insects and various diseases to which they are
subject. Pruning is carried out in May or June, after the flowering
period. The inner branches are carefully removed, also dead wood and
decayed growth.
The flowers, which expand towards the end of April, furnish on
distillation the sweet oil known as neroli oil, and orange flower water
as a by-product. Preference is given to the products of the bitter
orange, which differs from the sweet orange in its larger and more
numerous flowers, the leaves having larger winged petioles and the(^1) P. and E.O. R. (1916), 246.