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Indian Forest Records. 
[VoL. i 
Ngai camphor which is at present manufactured only in Hainan and 
Formoso and at Canton, so far as Eastern opinion regarding its excel- 
lence and peculiar virtues for medicine is concerned, is second only to 
Barus camphor. 
It will thus be seen that in point of commercial value Ngai camphor 
holds an intermediate position between Barus and common camphors. 
Methods of Assaying a Camphor-yielding Plant. 
The estimation of volatile oil is the chief thing in the analysis of a cam- 
phor-yielding plant or any plant which contains volatile oils. Besides 
this, water determinations are also made in such plants or their parts, 
both in their fresh green state and when they have been dried in the shade. 
These water determinations serve in comparing the yields (per cent.) of 
volatile oils from the plants in their fresh and dry states and further in 
comparing the oil determinations in different samples calculated on the 
dry material. 
Moisture Determination. 
The moisture determination is made as usual. About 3 — 4 grams of 
the leaves in small fragments or of the stem or of other parts of the plant 
carefully cut up into thin slices are accurately weighed and dried at 100°C. 
till the weight is constant. A slight inaccuracy in this determination 
occurs on account of most of the volatile portions of the plant escaping at 
100°C., and in consequence being calculated as moisture, but since the 
percentage of volatile oils is generally very small in the plants in question, 
the water determination may be regarded as (very approximately) correct 
for all practical purposes. 
Volatile Oil Determination. 
As the percentage of volatile oils in plants is generally low, it is rather 
difficult to determine exactly the percentage of the oil present. The 
estimation is generally made by two methods, which are described below. 
(1) By steam distillation. — A weighed part of the plant, sufficiently 
and suitably comminuted, in which the amount of volatile oils is to be 
determined, is distilled by passing steam over it, and the distillate consist- 
ing of condensed steam and volatile oil is shaken with ether, which dis- 
solves out the whole of the volatile oil present in the distillate. The etheral 
solution of the volatile oil thus obtained is then dried over calcium 
chloride, rapidly filtered and carefully distilled over. The residue is 
weighed as volatile oil. Obviously the results obtained by this method 
are only approximately correct. v 
