Chemistry of Essential Oils

132 THE CHEMISTKY OF ESSENTIAL OILS

c.c. =0

*

0001 grm. Pb.) added to the blank until the brown coloration

produced matches the sample under examination, the liquid being stirred

three times after each addition of standard lead solution by means of a

piston-shaped glass rod.

The results are calculated by means of the formula x = n x 0'04

-5- w, where x is the percentage of lead sought, n the number of c.c. of

standard lead solution required, and m the amount of original solution

taken. The tint of the solutions can be compared by looking through

the Nessler glasses resting on a white tile. But better results are

obtained by using a Duboscq colorimeter. The values for lead found by

this method are slightly high, the average excess found being 0*00018

grm. This correction may be applied if strictly accurate results are

required. The following were the results obtained on five oils in compari-

son with the results by gravimetric analysis :—

1

2

3

4

5

°/o found by

Gravimetric

Method.

0-0566

0-0524

0-0494

0-0546

0-0611

°/ 0 found by

Colorimetric

Method.

0-0536

00520

0-0512

0-0

0-0592

Difference.

+ 0'0030

+ 0'0004

• 0-0018

• 0-0026


• 0-0019
  Experiments were made on the lead-dissolving power of cassia oiL
  10 c.c. of the lead-free cassia oil was introduced into each of 22 test
  tubes, together with a strip of bright lead about 1 cm. broad and 6 cm.
  long. The tubes were then closed with clean corks, shaken at intervals,
  and tested at intervals. The amount of lead absorbed increased with the
  time, and reached a maximum of 0'074: per cent, after one month, and
  then seemed to remain constant. It is noteworthy that after that
  period the lead content exceeds the percentage found in commercial
  samples, which is, as a rule, from 004 to 0 06 per cent.

OIL OF CINNAMON.
The cinnamon oil (i.e. the bark oil) of commerce is understood to be
the product of distillation of the bark of Cinnamomum zeylaniciim, the
Ceylon cinnamon, a native of that island. The leaves and root bark
also yield essential oils, the former of which is of considerable impor-
tance commercially. The cinnamon tree is a small evergreen tree with
shining leaves and panicles of greenish flowers, of somewhat unpleasant
odour. It is extensively cultivated in Ceylon, from which nearly all
the bark of commerce is obtained. It is also grown in India, Mauritius,
the Seychelles and Jamaica, but Ceylon is responsible for practically
the whole of the cinnamon used. Several varieties are cultivated, but
whether they are merely the same plant slightly modified by the in-
fluence of soil, etc., or not, is uncertain. The Colombo, Negumbo, and
Matura districts in the south-west of the island produce the majority of
the bark, and the famous "cinnamon gardens" of Colombo, which oc-
cupy a considerable space, form one of the great attractions of the
island. The age of the tree, the care devoted to its cultivation, and the
time at which the bark is gathered largely determine the value of the
product. The appearance and size of the " quills," together with their
odour and flavour, determine their value on the market. The small
fragments or chips and the bark of inferior quality are used in Ceylon