THE PREPARATION OF CORN OIL. 5 



soapstock was heated to about 50° C. and rehardened by cooling, 

 more oil separated out and could be drained off. In this way the 

 refining losses were still further reduced. 



So far as refining loss is concerned, method 1 with 10° Be. caustic 

 and method 2 with 14° Be. caustic, using 50 per cent excess and 2 

 per cent soda ash, give satisfactory results. The oil resulting from 

 either method is low in free fatty acids, but that from method 1 

 appears to bleach somewhat better when treated with fuller's earth 

 and deodorized, which is due no doubt to the greater excess of 

 caustic used. 



After being treated by method 1 the oil is quite turbid, because of 

 a fine suspension of moisture and soap. That soap is present is evi- 

 denced by the fact that dehydration, while it clarifies the oil, leaves 

 fine particles in suspension, which gradually settle out on cooling. 

 Therefore, oils treated by this method must be washed in order to 

 remove the soap. The oil from method 2, although somewhat turbid, 

 evidently does not contain soap, because when the moisture is removed 

 the oil is absolutely clear. 



BLEACHING. 



Vegetable oils are usually bleached by means of fuller's earth or 

 finely divided carbon. Oils differ greatly in the ease with which they 

 can be bleached, corn oil being particularly difficult. In order to 

 formulate an exact method for bleaching this oil by means of fuller's 

 earth, several experiments were made to establish (1) the proportion 

 of earth necessary, (2) the proper temperature, and (3) the proper 

 length of treatment. 



In the first experiment four samples of a composite of caustic- 

 treated oils were used with 2, 4, 7, and 10 per cent of standard 

 fuller's earth, 6 respectively. One hundred grams of oil were heated, 

 with constant stirring, to 110° C. and kept at that temperature about 

 10 minutes to remove all traces of moisture. This treatment is consid- 

 ered necessary, because the earth does not effect a satisfactory bleach 

 if the oil contains any moisture. The temperature was held at 105° 

 C, while the earth was added slowly and the stirring continued for 

 five minutes. The oil was then rapidly filtered on a force filter. 

 Figure 1 shows the extent to which the several proportions of earth 

 removed the color. The readings in all cases were made in a 2-inch 

 cell with a Lovibond tintometer. The quantity of oil available in 

 these preliminary experiments was not sufficient to enable the use 

 of the 5i-inch cell, which is considered the standard. 



The results show, as was to be expected, that, within the range of 

 this experiment, the bleaching increases with the increase in the per- 



6 Standard fuller's earth is recommended by the American Oil Chemists' Society for bleaching vegetable 

 oils and may be obtained from the secretary of that society. 



