PRELIMINARY REPORT ON COLLOIDAL CLAYS AS EMUL¬ 
SIFIERS FOR MINERAL OILS USED IN SPRAYING 
CITRUS GROVES 1 
By W. W. Yothers, Associate Entomologist , Bureau of Entomology , and John R. 
Winston, Associate Pathologist , Bureau of Plant Industry , United States 
Department of Agriculture 
INTRODUCTION 
Soap emulsions of mineral lubricating oils have been used for 
many years in Florida for spraying citrus trees for the control of 
several species of scale insects and white flies. These are usually 
made according to the following formula: 
Mineral oil_gallons-- 2 
Water_do_1 
Caustic potash fish oil soap_pounds __ 2 
Several mineral oils have been used, but those used most extensively 
have the following physical specifications: 
Oil 
Specific 
gravity 
at 27° C. 
Flash 
point 
CO.) 
Fire 
point 
(° C.) 
Viscosity 1 
Volatility* 
Medium.. 
0.886 
184 
207 
365.3 
4.9 
Heavy... 
.896 
163 
245 
1 ,121.0 
.16 
1 Engler, H 2 0=100. 21 gram for 4 hours at 105° C. 
The materials are put into a kettle or other vessel that will stand 
fire and are heated to the boiling point—about 168° F. After re¬ 
moval from the fire, but while still very hot, the mixture is pumped 
with a bucket pump from the kettle to another receptacle, and back 
again. The formula just mentioned is sufficient for 197 gallons of 
water, making about 1 per cent of oil in the diluted spray material. 
These soap-mineral oil emulsions have given most satisfactory 
results from the standpoint of insect control. The simple soap emul¬ 
sions, however, have certain limitations which make them somewhat 
inconvenient for citrus growers. For example, they are not suffi¬ 
ciently stable to mix with “ hard” or deep-well water unless this water 
is first treated with chemicals to “soften” it; neither will they mix 
with lime-sulphur solution without the emulsions themselves being 
specially treated with a stabilizing agent. They will, however, mix 
with alkaline Bordeaux mixture in all proportions. 
The simple soap emulsions can be made to mix with any “hard” 
or deep-well water found in Florida citrus groves or with lime-sulphur 
solution by means of stabilizers such as glue, casein, milk powder, 
flour, corn starch, laundry starch, and water glass. When these are 
placed in the emulsions immediately before they are to be used 
satisfactory results have always followed; but if the organic materials 
are put into the emulsions any considerable length of time before they 
are to be used fermentation usually takes place and the entire emul- 
1 Received for publication Aug. 26, 1924; issued September, 1925. 
Journal of Agricultural Research, 
Washington, D. C. 
( 59 ) 
Vol. XXXI, No. 1 
July 1, 1925 
Key No. G-488 
