1919.) The Purification of Indian Sesame (Til) Oil. 327 
grm. of caustic soda). The period of alkali- ae varied 
from 5 to 30 minutes with intervals of 5 minutes each. The 
colour, though an improvement over that of the peeeu sample 
and better than that of the acid-treated samples, did not show 
any marked degree of uct sue 
e fifth set comprised t experiments. The oil was 
treated with different pao ie of the alkali solution varying 
from 1 ¢.c. to 10 c.c. with a constant difference of 1 ¢.c. The 
period of as alkali- contact, before washing with water, was 
one hour in every case. 
In samples Nos. 25, 26, and 27, containing | c.c., 2 c.c., 
and 3 c.c. of the alkali solution respectively, a slight progres- 
sive improvement both in colour and odour was observed. 
Sample No. 28, containing 4 c.c. of the alkali solution, showed 
a marked improvement. Samples Nos. 29 to 34, though con- 
taining different and increasing amounts of alkali, exhibited 
exactly the same degree of improvement both in colour and 
odour. Thus s ample No, 28, containing 0°3792 grm. of caustic 
soda per 100 c.c. of the oil, marked a critical point in the 
improvement of the oil. Further, it is obvious that the mini- 
mum quantity of caustic soda required for the purification of 
the oil is 0°4740 grm. per 100 c.c. of the oil. 
e of experiments were performed with 1,000 c.c 
of the commercial oil which was treated with an alkali solution 
containing 0°5 gram of caustic soda. The oil showed an ex- 
cellent ee a both in colour and odour. 
t may be noted that the above results hold good in the 
case of eres variety of the oil used for the experiments, and 
will have to be modified slightly when applied to the com- 
mercial sesame oil which is “to be met with in several grades 
on the market 
On # arming the treated samples the odour is perceptible 
and not unpleasant but of a nature quite different from that 
of the control sample. On cooling, however, the odour dis- 
rs. 
a 
ae When’a mixture of ' ghee’ (the so-called clarified butter 
in India) and the treated oil is warmed, its odour resembles 
that of rancid ‘ghee.’ It is most likely that the odour of the 
oil is masked by that of the ‘ ghee.’ On cooling the odour of 
epil is not perceptible. The same remarks apply to the 
oil treated with sulphuric acid. 
SuMMARY AND CONCLUSION. 
The Biss tes of the investigation may be summarised as 
follows 
(1) Of all the filtering materials, used for the purification 
of the oil, bone charcoal and French chalk (precipi- 
