6 BULLETIN 1332, U. S. DEPARTMENT OP AGRICULTURE 



From these measurements it is apparent that there is an optimum 

 proportion of soap above which there is on standing a marked sepa- 

 ration of the soap from the emulsion and below which there is a tend- 

 ency for the globules to increase in size to such an extent that the 

 mixture either fails to emulsify or easily breaks after emulsification. 



Soaps vary greatly in emulsifying power, some brands being use- 

 less and, in fact, two batches of the same brand may vary greatly in 

 emulsifying power (7). Under these circumstances the writers found 

 it necessary to test each purchase of soap before emulsifying any 

 quantity oi wormseed oil for experimental purposes. In practice, 

 in the hands of the novice, any deficiency in the soap used might 

 easily result in an unstable emulsion. The writers therefore made a 

 series of tests to determine the possibility of preparing wormseed-oil 

 emulsion by means of such standard materials as oleic acid and 

 sodium or potassium hydroxide, according to the equation — 



C 8 H 17 CH :CH(CH 2 ) 7 COOH + NaOH = H 2 + C 8 H 17 CH :CH 

 (CH 2 ) 7 COONa. 



In making these emulsions the oleic acid was added to the oil and 

 shaken, then N/10 NaOH or N/10 KOH was added. The mixture 

 emulsified immediately. 6 The various tests are compared in Table 3. 7 



In using these emulsions in practice it seems advisable either to 

 use the oleic acid or, if a commercial brand of soap is employed, to 

 be absolutely sure by test that the material will produce a stable 

 emulsion. 



Table 3. — Preparation of wormseed-oil emulsions with oleic acid and an hydroxide 



Emulsion number 



Quantities of — 



N/10 

 NaOH 



Remarks on emulsions formed 



Oil 



Acid 



1A 



C. c. 

 20 

 20 

 20 

 20 

 20 

 20 

 20 



C.c. 

 0.12 

 0.24 

 0.40 

 0.80 

 1.20 

 1.60 

 2.00 



C.c. 

 3.76 

 7.56 

 12.60 

 25.20 

 37.80 

 50.40 

 63.00 



Oil separated out in 1 hour. 



2 A 



Oil separated out in 1 hour. 



3 A 



Stable emulsion. Best of series. 



4A 



Stable emulsion. 



5 A 





6A 



7 A 



Curdy emulsion. Too much emulsifier. 

 Curdy emulsion. Too much emulsifier. 







Emulsion 



Quantities of — 



N/10 

 KOH 



Remarks on emulsions formed 



Oil 



Acid 



8 A 



20 

 20 

 20 

 20 

 20 



0.20 

 0.40 

 0.60 

 0.80 

 1.00 



6.30 

 12.60 

 18.90 

 25.20 

 31.50 



Oil separated out. 



9 A 



Stable emulsion. Best of series. 



10 A 





11 A 





12A 









6 The molecular weight of oleic acid is 282.37 and its specific gravity is 0.89; it follows that 317.3 cubic centi- 

 meters of the acid will make a normal solution. Therefore 317.3 cubic centimeters of oleic acid is neutrali- 

 zable by 1,000 cubic centimeters of normal sodium hydroxide, or 0.03173 cubic centimeter of oleic acid by 1 

 cubic centimeter N/10 sodium hydroxide. Conversely, 1 cubic centimeter of oleic acid is neutralizable by 

 31.5 cubic centimeters of N/10 NaOH. 



7 The writers have been guided in the preparation of these emulsions by Clayton (1) . 



