4 BULLETIN 1010, U. S. DEPARTMENT OF AGEICULTUEE. 



in 10, 50, 100, and 200 per cent excess. Table 2 shows the results of 



these tests. 



Table 2. — Results of using 10, 50, 100, and 200 per cent excess of 14° Be. caustic vjith 



method 2. 



Exper- 

 iment. 



Excess 

 caustic 

 used. 



Quantity 



of soda 



ash. 



Refining 

 loss. 



Free 

 fatty acid 

 after 

 treat- 

 ment. 



Character of settling and condition of soapstock. 



No. 15.... 

 No. 16.... 



No. 17.... 



No. 18.... 



Per cent. 

 10 

 50 



.100 

 200 



Per cent. 

 1.5 



1.5 



1.5 

 1.5 



Per cent. 

 9.0 

 8.2 



8.0 

 7.2 



Per cent. 

 0. 051 

 .041 



.033 

 .070 



Soapstock very soft and slimy. 



Soapstock slightly more compact than that in ex- 

 periment 15, but slides in mass. 



Soapstock very much like that in experiment 16. 



Soapstock very much like that in experiments 15 

 and 16. 



The foregoing tests show that although not enough soda ash was 

 used to make the soapstock firm it resulted in the soapstock settling 

 to a much thinner layer, so that much less oil was occluded. A num- 

 ber of experiments were performed in which other dehydrating sub- 

 stances were used; namely, anhydrous sodium sulphate, calcium 

 sulphate (plaster of Paris), and common salt. Of these substances 

 only the dry sodium sulphate compared favorably with the commer- 

 cial soda ash in the hardening effect upon the soapstock. Table 3 

 shows the effect of using larger quantities of soda ash in connection 

 with method 2. 



Table 3.- 



-Effect of the use of 2 and 3 per cent of soda ash on the soapstock in connec- 

 tion with method 2 under several conditions. 



Experiment. 



Strength 



Excess 



Quantity 



of caustic 



caustic 



of soda 



used. 



used. 



ash used. 



"Be. 



Per cent. 



Per cent. 



14 



50 



2 



14 



50 



3 



14 



100 



2 



14 



100 



3 



14 



200 



2 



14 



200 



3 



Refining loss — 



By pour- 

 ing off 

 the oil. 



After 

 heating 

 and re- 

 cooling 



soap- 

 stock. 



Condition of soapstock. 



No. 19. 

 No. 20. 

 No. 21". 

 No. 22. 

 No. 23. 

 No. 24. 



Firm. 



Do. 

 Very firm. 



Do. 

 Verv firm and bulky. 

 'Do. 



It will be seen from Table 3 that the refining loss can be very materi- 

 ally reduced by the use of 2 per cent of soda ash in connection with 

 method 2, whether the excess caustic used is 50, 100, or 200 per cent. 

 The use of an additional 1 per cent is of no advantage, because a 

 greater bulk of soapstock results, with a consequent greater occlu- 

 sion of oil. In all these tests the soapstock was firm and permitted 

 the thorough draining off of the oil. It was found that when the 



