When finely powdered and rubbed down with water they form emulsions, the undissolved resin being suspended in the gum solution.
As a rule, however, it is a very precarious one, since emulsions are formed which prevent in many cases the separation of oil altogether.
An important property of waxes is that of easily forming emulsions with water, so that large quantities of water can be incorporated with them (lanolin).
For pharmaceutical purposes crude petroleum is no longer generally used by civilized races, though the product vaseline is largely employed in this way, and emulsions of petroleum have been administered internally in various pectoral complaints; while the volatile product termed rhigolene has been largely used as a local anaesthetic.
The dipterous garden pests, such as the onion fly, carrot fly and celery fly, can best be kept in check by the use of paraffin emulsions and the treatment of the soil with gas-lime after the crop is lifted.