December,’23] burroughs & grube: lubricating oil emulsions 537 
for a short time. These stock emulsions can be made by means of a 
power sprayer. The ingredients are put in a half barrel or other con¬ 
tainer and the suction hose and a hose from the return line placed in the 
container. The mixture is then pumped from one receptacle to another 
until emulsified. 
The emulsions made in the manner described above have larger oil 
globules than the oil-soap emulsions. Those made by means of the 
basic metal hydroxides have a tendency for a little oil to separate out 
after a time. This can be emulsified again by re-pumping. The emul¬ 
sions so made do not separate spontaneously in the presence of hard 
water, lime-sulphur, or in containers contaminated with lime or lime- 
sulphur, as do the soap emulsions. 
When diluted with water, the emulsions tend to rise to the top, but 
can be kept properly mixed by the degree of agitation obtained in a power 
sprayer. By emulsifying the oil with a relatively large amount of Bor¬ 
deaux or iron sulphate-lime mixture, an emulsion can be made which is 
heavier than water, and which can be more easily kept stirred by the 
agitators. If the right proportions are used, an emulsion with a specific 
gravity of 1 can be made. Pickering 4 gives the formula for such an 
emulsion of solar distillate. 
Pickering believed that, where the so-called insoluble emulsifiers were 
used, the oil globules were surrounded by minute solid particles of the 
emulsifier. Text books, 5 6 7 give other explanations of the action of 
emulsifying agents in general, but most of them mention that Pickering’s 
emulsions are exceptions to the general rule. 
Holmes 5 describes the ideal emulsifying agent as a solvated colloid 
giving a tough elastic film, gelatinous and swollen on the side of the 
continuous phase (water) and coagulated and slightly wetted on the 
side of the dispersed liquid (oil). The proteins, alkali soaps, and the 
other hydrated colloids which can act as emulsifying agents for engine 
oils, fulfil the requirements of this theory. Holmes evidently believes 
that the emulsions made with Bordeaux mixture differ from those 
having hydrated colloids as emulsifiers. Yet Duggar and Bor.ns 8 
consider dried Bordeaux films to be capable of hydration. Collodial 
metal hydroxides are able to hold in combination a large amount of 
water. Clay was one of Pickering’s “solid emulsifiers,” yet under some 
conditions, clays are highly hydiated. It may be that the basic sul- 
5 Holmes, N. H. Laboratory Manual of Colloid Chemistry. N. Y., 1922. 
6 Bancroft, W. D. Applied Colloid Chemistry, N. Y., 1921. 
7 Clayton, W. The theory of Emulsions and Emulsification. Philadelphia, 1923. 
8 Annals of Mo. Botanical Garden, 5: 153, 1918. 
