EMULSIONS FOR JAPANESE BEETLE 



internal phase. Various hydrophile colloids such as soap, glue, gum 

 arable, etc., were tested in this connection as emulsifiers. In each 

 case the colloid was dissolved in hot water, added to the wormseed 

 oil, and shaken until the emulsion formed. In this manner 15 cubic 

 centimeters of a 20 per cent gum arabic solution added to 10 cubic 

 centimeters of oil gives a stable emulsion; 20 cubic centimeters of 

 0.5 per cent agar-agar and 5 cubic centimeters of oil produced a 

 stable emulsion; 10 cubic centimeters of a 2 per cent glue solution 

 added to 5 cubic centimeters of oil proved to be a very stable emulsion. 

 Dextrin, saponin, and starch were found of little value in this con- 

 nection. 



While the results with miscellaneous colloidal emulsifiers as 

 described above were satisfactory, the major part of the work was 

 done with soap as the emulsifier, since this colloid appeared the most 

 satisfactory of all. A commercial brand of caustic potash fish-oil 

 soap diluted with water was mixed with the oil in varying proportions 

 and shaken. In the majority of cases no emulsification occurred. 

 Another procedure was then undertaken; the undiluted soap was 

 first mixed very thoroughly with the oil, giving a so-called "miscible 

 oil" which when mixed with water gave a perfect emulsion in the 

 instances where sufficient soap was present. The length of time 

 required for emulsification varied directly -with the concentration of 

 the soap. 



STABILITY OF THE EMULSIONS 



Emulsions were obtained with 20 cubic centimeters of oil and 

 amounts of soap varying from 10 cubic centimeters down to 0.5 

 cubic centimeter. A mixture of 0.25 cubic centimeter of soap to 

 20 cubic centimeters of oil failed to produce an emulsion, probably 

 owing to the fact that not sufficient soap was present to form a film 

 at the oil-water interface. 



The question therefore arose as to the optimum amount of soap. 

 It was thought that within certain limits the greater the amount of 

 soap present the more thorough would be the division and the smaller 

 the size of the oil globules; in other words, the finer the water suspen- 

 sions and the more stable the emulsion the greater would be the 

 number of oil globules, the greater the surface of the oil-water inter- 

 face, and, therefore, the greater the amount of soap necessary. If 

 this hypothesis is accepted it must be assumed that there would be 

 either an increase in the size of the oil globule with the decreased 

 amount of soap or a diminution in the thickness of the soap film on 

 the surface of the globule. Upon measurement it was found that 

 there was an actual increase in the size of the globule, thus explaining 

 the decreased stability of the emulsion with the decreased amount 

 of soap. The measurements are given in Table 2. 



Table 2.— Stability of wormseed-oil emulsions prepared with potash fish-oil soap 





Ingredients of emulsion 



Size of globules 



Remarks 



Emulsion number 



Soap 



Oil 



u ater 



1 



C.c. 



10 



r, 



2.5 

 I 



0.6 

 0.26 



C.c. 

 20 

 20 

 20 



20 



20 



20 



C. c. 



I0 

 10 

 10 

 10 

 10 

 10 



Micron* 

 1 to 12 



Stable; best emulsion. 



2 



2 1,o Hi 



Stable. 



3 



4 to 32 



i fnstable, 



■1 



6 to 42 



Unstable, 



6 





i ii itable. 



6 





Did not emulsify. 









