THE PREPARATION OF CORN OIL. 3 



The oil is placed in a suitable container equipped with a mechanical stirrer and 

 agitated constantly while the caustic solution is slowly added. After being stirred 

 for five minutes, to insure a thorough mixing, the oil is gently heated to 55° C. over a 

 15-minute period . When the oil approaches this temperature it breaks. 5 The stirring 

 is now stopped and the oil allowed to stand for three hours at a temperature of 50° to 

 55° C. . After cooling, it is separated from the deposited soapstock. In the experi- 

 ments in which small quantities were used in beakers, the refining losses were deter- 

 mined by pouring off the oil from the soapstock. 



In the first experiments with method 1, caustic solutions of 10°, 

 12°, 14°, and 16° Be. were used, while with method 2 the solutions 

 used were of 5°, 10°, 14°, and 20° Be. strength. In each case the 

 test was made on 100 grams of oil. With method 2, 10 per cent of 

 caustic in excess of the quantity necessary to neutralize the free fatty 

 acids was used. The results are shown in Table 1. 



Table 1 . — Results of treating corn oil with several concentrations of caustic in connec- 

 tion with methods 1 and 2. 



Method and 

 number of 

 exper- 

 iment. 



Strength 



of caustic 



used. 



Refining 

 loss. 



Free 



fatty 



acids in 



treated 



oils. 



Character of settling and condition of soapstock. 



Method 1: 

 1 



2 



3 



4 



Method 2: 



5 



6 



7 



8 



° Be. 

 16 



14 



12 

 10 



20 

 14 

 10 

 5 



Per cent. 

 8.47 



5.7 



5.0 

 4.6 



27.5 

 11.7 

 11.9 

 12.5 



Per cent. 

 0.033 



.031 



.037 

 .047 



.076 

 .047 

 .026 

 .056 



Rapid settling; soapstock is light and flaky and occludes 



much oil. 

 Soapstock very much like that in experiment 1, but appears 



to contain less oil. 

 \ Soapstock forms a semiliquid layer which hardens to soft 

 / petrolatum consistency on cooling. 



Soapstock very slimy and does not settle firmly. 



{•Settles more rapidly than in experiment 5; soapstock slides. 



Soapstock liquid when hot; does not harden entirely on 

 cooling. 



The soapstock obtained by the two methods differs greatly. That 

 obtained by method 1 is in all cases semiliquid while warm, and on 

 cooling hardens to a consistency like that of soft petrolatum. Such 

 soapstock occludes very little oil, with attendant low refining losses. 

 It appears that the weaker concentrations of caustic, such as 10° 

 and 12° Be., give better results on corn oil. 



Method 2 results in very high refining losses, because the soapstock 

 in practically all cases is very slimy and occludes much oil. Ac- 

 cordingly, the most suitable concentration to use is apparently a 

 strength of 14° Be. It is evident that with this method it is benefi- 

 cial to add some material to harden the soapstock in order to reduce 

 the refining losses. 



The next series of experiments was for the purpose of determining 

 the quantity of excess caustic that should be used in method 2. In 

 all cases 1.5 per cent of soda ash was added after the break, in order 

 to harden the soapstock. Caustic of a strength of 14° Be. was used 



6 The appearance given to oil when coagulations of soap occur during refining. 



