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digestion in petroleum-ether, and the extent to which they are capable of
absorbing and losing moisture ascertained during the time the powder is being
treated with petroleum-ether, the flasks being agitated daily during this time.
After thorough digestion it is to be noted if any petroleum-ether has been
lost; if so, sufficient petroleum-ether should be added to make up 100cc. With
a pipette 20 to 25cc. of the supernatant fluid should be drawn off and placed in
separate small flask to be used for quantitative determinations. The remainder
is to be filtered, the residue washed with petroleum-ether till the solvent passes
through uncoloured, and the filter and residue dried at the ordinary temperature
for a day by aspiration and afterwards under a bell-jar beside strong sulphuric
acid. When quite dry the substance is to be removed from the filter (which
must be kept for subsequent solutions) and placed, in the same flask as was used
for petroleum-ether, with 100cc. ether and left to digest for eight days. The
interval may be utilised in examining the petroleum-ether extract.
When the substance has been thoroughly digested with ether with frequent
agitation, sufficient ether having been added, if necessary, to make up to 100cc.,
enough may be drawn off for quantitative analysis and the rest filtered throug
h t h e s a m e f i l t e r a s w a s u s e d f o r p e t r o l e u m - e t h e r . T h e e t h e r s o l u t i o n s h o u l d
be allowed to evaporate spontaneously, and the filter and residue dried by
aspiration or beside sulphuric acid. When quite dry the residue is to be remov
e d f r o m t h e f i l t e r , t h e f i l t e r k e p t f o r f u t u r e u s e , a n d t h e s u b s t a n c e p l a c e d i n t h e
same flask as before with 100cc. absolute alcohol and left to digest for eight
days The interval may be utilised in examining the ether extract.
When thoroughly digested with absolute alcohol, filtration will again
take place through the same filter after sufficient alcohol has been added to
make up to 100cc., and after sufficient supernatant solution has been drawn off
with a pipette for quantitative estimation. The filter and substance well washed
with alcohol may be dried in a water-bath at 60°C. and kept under a bell-jar till
the examination of the alcoholic extract is completed.
The residue is then removed from the filter and placed in the same
flask with100cc. distilled water and digested with much agitation for several
hours. Filtered through the same filter as before, a measured quantity of the
filtrate should be taken for quantitative estimation.
Beyond this point it is not necessary to go, since both the residue and
watery extract should be found inert.
I. Examination of the petroleum-ether extract.
1. Estimation of the essential oil.
5cc. of petroleum-ether solution was drawn off by a pipette and placed
in a tared glass dish with vertical sides and ground-glass cover. This was placed
under a bell-jar and aspirated with dried air at ordinary temperature till Petro-
leum-ether ceased to be present. The 'co-efficient of evaporation' obtained by
weighing after intervals of one minute—the tared dish during weighment closed
by its glass cover—will probably not be ascertained; there seems not to occur a
period when there is a constant rate of evaporation of oil. When the petroleum
-ether ceases to be given off, the extract left does not at a temperature of 86°F.
appreciably lose weight, though left for a day. When the dish and extra
ct recorded the same weight at three (instead of, as is more usual, two) successive
weighments, the weight was noted; the correction for petroleum-ether residue
deducted; the resulting number was then recorded as Total Petroleum-Ether
Extract. The dish was then placed in an air-bath, and heated to 110°C.
weighed till weight was constant; the weight noted was then subtracted from
the weight recorded as total petroleum-ether extract, and the result given as
essential oil.
In the case of gánjá of 1892-93, the results were:—
W e i g h t
of 5cc.
Petro-
leum
ether.
C o r r e c t i o n f o r 5 c c . P e t r o - l e u m
ether.
Total
petro-
leum
ether
extract
weight
5cc..
Per
cent.
A f t e r a s p i r a t i o n . . .
Round ... 0.1300–0.0064=0.1236=24.72
Flat
... 0.1330—0.0064=0.1266=25.32
After air- bath 11000 . .
.
Round ... 0.0925=18 53%
Hence,
Flat ... 0.0948=18 96%
Essential oil . . .
Round ...
24.72—18.53=6.19%
Flat ...
25.32—18.96=6.20%