Factors Concerned in the Deposit of Sprays: V. The Effects of pH Upon the Deposit of the Oil and Water Phases of Oil Emulsions*†

In previous reports from this laboratory (Ben-Amotz & Hoskins 1937; Hoskins & Ben-Amotz 1938), it has been shown that the amount of oil which is deposited when a given volume of an oil emulsion is sprayed upon a standard beeswax surface is influenced greatly by the nature and concentration of the accessory substance, often called the spreader, emulsifier or wetting agent. With blood albumin or hemoglobin, both of which enable the aqueous phase to wet the solid readily but which are relatively weak emulsifying agents, the oil deposit passes through a maximum at some intermediate concentration of the accessory substances. With sodium oleate, which possesses the above properties in the reciprocal ratio, there is a continuous decrease in oil deposit as more of the soap is used. A somewhat similar difference in the amounts of emulsion (oil plus aqueous phase) deposited is brought about by these accessory substances. With the proteins this increases as their concentrations increase, but sodium oleate over the range of concentration used (0 to 852 milligrams per gallon) has but little effect upon the amount of emulsion deposited.