UMBELLIFEE^E (^305) »
Bavaria, wild 6-5 to 7 per cent.
Finnish........ 5 to 6
Hessian, wild 6 „ 7
Moravian, cultivated ...... 4
East Frisian 5-5 to 6
Russian, wild 32 „ 3-6
Styrian 6
Wurtemburg 5-5 to 6
German, cultivated ...... 35 „ 5
Galician .......... 4-5
Dutch, cultivated 4 to 6 5
Norwegian, wild....... 5 ,, 6-5
East Prussian, cultivated..... 5 ,, 5-5
Swedish, wild 4 „ 6'5
Tyrolese 65
Caraway oil has the following characters :—
Specific gravity 0-910 to 0-918 (rarely 0-907>
Optical rotation + 70° to + 82° 30'
Refractive index 1-4840 to 1-4890
Carvone 50 to 60 per cent.
As caraway oil consists almost entirely of carvone, of specific gravity
0964, and limonene of specific gravity 0
- 850, the amount of carvone
present can be very approximately deduced from the specific gravity of
the sample.
Various direct methods of determining the carvone have been pro-
posed, based on the preparation of crystalline compounds of this body.
The oxime, the sulphuretted hydrogen compound, and the phenylhydra-
zone have been employed, but only approximate results can be obtained
in all these cases. The following are the details recommended in the
case of the phenylhydrazone :—
When 5 c.c. phenylhydrazine are added to 5 c.c. of caraway oil the
mixture becomes warm owing to chemical combination taking place, and
if the action be accelerated by placing the test tube in boiling water for
a few minutes a copious crystallisation of carvone phenylhydrazone,
C 10 H 14 : N. NH. C 6 H 5 , appears, and on cooling the whole solidifies to
a crystalline mass. After heating for one hour the reaction is complete,.
the excess of phenylhydrazine is removed by adding 5 c.c. glacial acetic
acid whilst hot, shaking, and diluting with 20 c.c. water. The contents,
of the test tube are then cooled and filtered through a paper disc by
means of a pump, and the crystalline mass washed with water until
1
of a pale yellow colour. By this process not only is the excess of phenyl-
hydrazine removed in aqueous solution as acetate, but nearly all the oily
terpene adherent to the crystals is washed away. On crystallising from
a definite volume of 95 per cent, alcohol the carvone phenylhydrazone is
obtained in long silky pale yellow needles, melting at 106° C., but so-
difficult to dry without decomposition as to render the determination
only approximate.
The sodium sulphite process yields good results. On fractional dis-
tillation not more than 25 per cent, should distil below 185° and at least
55 per cent, to 65 per cent, should distil over 200°, a considerable frac-
tion—40 per cent, to 50 per cent.—being obtained from 220° to 230°.
The valuable constituent of this oil is the carvone, and on this
account, and as it is easy to separate this body in a fairly pure state,
carvone is often used in place of the oil, and is official in the German
Pharmacopoeia. The result is that there is much de-carvonised oil on
VOL. i. 20