IN regard to the origin of crude oil emulsions, it is held nowadays that they are not formed until they are mined. Factors which may give rise to their formation are: The concurrent pumping of the oil and the water; the passage of the two liquids through pipes; then the development of gas or the movement of gas. Almost invariably emulsions are thus formed in which the water is distributed in the oil; only sporadically are emulsions of oil in water formed. Many of the emulsions contain the water in a coarsely divided state and, if stand, cede it readily, though sometimes, to do this, the emulsion has to be slightly heated. Others, on the other hand, require special treatment necessitated by the presence of substances which have the property of preventing the drops of water from coalescing; these substances are called "emulsifiers."These emulsifiers are present in the crude oil, while clay may also act as an emulsifier. The action of these substances has to be eliminated. For the better comprehension of various processes, a few of the properties of emulsions and emulsifiers are passed under review. The emulsifiers in water-in-oil emulsions are mostly soluble or dispersable in the oil, whereas in the other type they are, on the other hand, water-soluble substances or are readily dispersed in the water. The most divergent kinds of matter may prove to be emulsifiers; there are molecularly soluble substances (colloids) and also more coarsely divided substances (suspen sions).They must, however, have the property of preferably accumulating in the interface between the oil and the water; in other words, they must be capillarily active and, by the properties which they develop in the interface, prevent the particles from coalescing. Usually the emulsifier impresses its mark upon the properties of the emulsion; in nearly every case it determines whether a water-in-oil or an oil-in-water emulsion shall continue to exist as such. Now, the chemical separation of emulsions is based in many instances on the fact that emulsifiers of contrary types counteract each other. Thus, by adjing an emulsifier of the contrary type, one can destroy or diminish the protective action of the emulsifier in the interface, by means of which the emulsion can be made to coagulate. Sometimes, however, the separation of crude oil emulsions is effected by emulsifiers which in themselves may often stabilise emulsions, which, from the point of view of the knowledge of emulsions of water in oil, must on the whole be regarded as remarkable. Other substances may also sometimes be used as emulsion coagulators. Little can be predicted about these, and although, so far as the agents required for separation are concerned, the oils mày be roughly classified, it has been found that the large number of emulsions that occur in practice demand the use of a large number of different substances.

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