be easily gauged by the appearance of a
cooled sample of the oil.

The potassium bichromate is dissolved in hot water and added to the
crude palm oil, previously heated to 125 deg. F. (52 deg. C.), the requisite
amount of muriatic acid being then run in and the whole well agitated by
means of air. The bright red colour of the oil gradually changes to dark
brown, and soon becomes green. The action having proceeded for a few
minutes, agitation is stopped, and, after allowing to settle, the green
liquor is withdrawn.

When sufficiently bleached the oil is finally washed (without further
heating) with hot water (which may contain salt), to remove the last
traces of chrome liquor.

If the above operation is carried out carefully, the colouring matter
will be completely oxidised.

It is important, however, that the temperature should not be allowed to
rise above 130 deg. F. (54 deg. C.) during the bleaching of palm oil, otherwise
the resultant oil on saponification is apt to yield a soap of a "foxy"
colour. The bleached oil retains the characteristic violet odour of the
original oil.

It has been suggested to use dilute sulphuric acid, or a mixture of this
and common salt, in the place of muriatic acid in the above process.

_Crude Cotton-seed Oil._--The deep colouring matter of crude cotton-seed
oil, together with the mucilaginous and resinous principles, are removed
by refining with caustic soda lye.

The chief aim of the refiner is to remove these impurities without
saponifying any of the neutral oil. The percentage of free fatty acids
in the oil will determine the quantity of caustic lye required, which
must only be sufficient to remove this acidity.

Having determined the amount of free acidity, the quantity of caustic
soda lye necessary to neutralise it is diluted with water to 12 deg. or 15 deg.
Tw. (8 deg. or 10 deg. B.), and the refining process carried out in three
stages. The oil is placed in a suitable tank and heated by means of a
closed steam coil to 100 deg. F. (38 deg. C.), a third of the necessary weak
caustic soda lye added in a fine stream or by means of a sprinkler, and
the whole well agitated with a mechanical agitator or by blowing a
current of air through a pipe laid on the bottom of the tank.

Prolonged agitation with air has a tendency to oxidise the oil, which
increases its specific gravity and refractive index, and will be found
in the soap-pan to produce a reddish soap. As the treatment p