MAGNOLIACEJE 505
The oil is soluble in 3 volumes of 90 per cent, alcohol.True Aniseed Oil.Specific gravity at 20° 0'980 to 0*990
Optical rotation 0° to - 2°
Refractive index.......1-5560 to 1*5590
Congealing-point16°,,16" „ 18°
Melting-point 17° , ,20°The oil is soluble in 3 volumes of 90 per cent, alcohol.
The usual adulterants are petroleum, fennel oil, or its stearoptene,
and the waste liquid portion of the oil obtained in the manufacture of
anethol (the solid odorous constituent of the oil). In addition, spermaceti
has been said to be added, but the author has never met with a sample
adulterated with this body. The value of the oil depends on the quantity
•of anethol it contains, and as this melts at 21° to 22° and boils at 232°,
the melting-point and the behaviour on fractionation of the oil yield most
valuable information as to its purity. With regard to the latter, the
frac ion obtained between 225° and 235° should not be less than 80 per
<5ent.—usually varying from 80 to 85 per cent.—corresponding to prac-
tically that quantity of anethol. Anethol has a great tendency to exist in
a state of superfusion, so that the oil can be easily cooled down, if not
agitated, below its normal solidifying-point, consequently it is necessary
•either to solidify the oil in a very thin test-tube, and taking its melting-
point, or to determine its solidifying-point in Beckmann's apparatus.
Schimmel & Co. describe the method they adopt in the following
terms, and the author considers it yields very concordant results:—
" For the determination of the point of solidification of essential oils,
ithe well-known Beckmann's apparatus for the determination of the
molecular weight from the decrease of the freezing-point may well be
used. A few small modifications make it particularly suited for the ex-
amination of anise and star-anise oils. These slight alterations consist
mainly in the removal of the cork-connections, by which the full view
of the mercurial column of the thermometer is impeded. The lateral
branch of the freezing tube of the Beckmann's apparatus, serving for
the introduction of the substance to be examined, can also be omitted.
The battery jar serves for receiving the refrigerating fluid. The test tube
suspended in the metal cover serves as aircover around the freezing tube,
preventing the premature solidification of the oil to be examined. This
tube is wider at its top, narrowing down at the junction where it rests on
the rim of the lower tube. In order to support the freezing tube, three
glass protuberances are affixed on its inside about 5 c.c. below its upper
rim. The thermometer, divided into •£ degrees, is supported in a metallic
cover by three small springs, permitting a ready displacement both up-
wards and downwards.
" For making the determination for anise and star-anise oils, the jar
is filled with iced water and broken ice, for fennel oil with a freezing
mixture consisting of broken ice and common salt. Then the sample of
oil to be tested is introduced into the freezing tube, reaching to a
height of about 5 cm., and the thermometer is inserted into the oil with
the precaution not to touch the wall of the tube in any place. During
the cooling process any concussions have to be avoided, as they tend to
cause a premature solidification of the oil. When the thermometer has