28 BULLETIN 867, U. S. DEPARTMENT OF AGRICULTURE. 



torn, 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 yellow. 



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 read}? - 

 for market. 



