EMULSIONS FOR JAPANESE BEETLE 
internal phase. Various hydrophile colloids such as soap, glue, gum 
arabic, 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 
Emulsion number 
Ingredients of emulsion 
Size of globules 
Remarks 
Soap 
on 
Water 
1 
C. c. 
10 
5 
2.5 
1 
0.5 
0.25 
C.c. 
20 
20 
20 
20 
20 
20 
C. c. 
10 
10 
10 
10 
10 
10 
Microns 
1 to 12 
Stable; best emulsion. 
2 
2 to 16 
Stable. 
3 
4 to 32 
Unstable. 
4 
6 to 42 
Unstable. 
5 
Unstable. 
6 
Did not emulsify. 
