H H H H H

II I II HHHHH

where R is an alkyl chain with ยก8 carbon atoms. The diamine acts as an O/W emulsifier as well as a wetting agent. The cation's nonpolar tail dissolves in the oil phase, and the nitrogen polar end extends into the water, thus imparting a positive charge to the oil droplet. Because most metal and mineral surfaces carry a negative surface charge, the oil droplets are attracted to the surface, where they break, depositing a film of oil as shown in Figure 7-10. Many other hydrocarbon-nitrogen compounds may be used as combined wetting agents

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