28 BULLETIN 867, U. S. DEPARTMENT OF AGRICULTURE. 
tom, with. just enough motion to insure good movement between the two phases 
without emulsifying them, it is found that all soap.can readily be removed. If an 
emulsion should form, it can be broken by. heating the oil and sprinkling in salt, with 
such agitation as has been described. Upon the settling out of the brine, it is drawn 
off and the oil dried and filtered. - 
No bleaching has been effective for the regular commercial types 
of No. 3 castor oil. This is attributed to the fact that the present 
practice has fixed the color by overheating and at the same time has 
introduced iron salts, due to the action of the comparatively high 
acidity upon the container walls. It has been found that castor oil, 
though highly colored, can be refined by alkali treatment and bleach- 
ing only when the oil has been treated with the same care that applies 
to any other oils intended for bleaching. A greenish yellow extracted 
oil has been successfully bleached, as well as a green oil produced by 
expelling castor beans in their original hulls or pods, but no success 
has been attained in endeavoring to bleach any of the commercial 
types of No. 3 oil, whether green or brownish vellow. 
BLEACHING. 
Castor oil coming directly from the presses or expellers is of a 
brownish gray color, due to suspended meal and droplets of water. 
Inasmuch as the oil produced by cold pressing or expelling runs low 
enough in acid to be satisfactory for the general purposes for which 
No. 1 castor oil is intended, it is not refined in practice, but merely 
cleaned up and bleached. Before satisfactory filtering and bleaching 
can be accomplished the oil must be dried. This is effected by 
heating the oil either at atmospheric pressure or in vacuum. Such 
equipment consists of an oil tank with closed coils, agitator, sight 
glasses, and a small 4-inch entrainment, which seems small but is 
ample to carry off the comparatively small amounts of water. Closed 
steam coils supply the necessary heat. Effective agitation is neces- 
sary to bring the moisture-bearing portions to the surface for ready 
drying. The oil may be circulated by pumping from the bottom 
and in at the top in the form of a spray, which, of course, operates to 
minimize the period of heating. After such drying is effected the 
oil is pumped to a mixing kettle and treated with fuller’s earth and 
carbon. The practice differs in different plants and according to the 
grade of the oil. A common method is to heat the oil to approxi- 
mately 200° F., preferably in vacuum, and then add from 2 to 4 per 
cent of a good grade of dry fuller’s earth. This mass is agitated for 
half an hour and then a good grade of bleaching carbon is introduced, 
varying from 0.2 to possibly 1.5 per cent, according to the grade of 
oil and quality of product desired. The oil is filtered and is then som 
for market. 
