The use of zeta potential to investigate the pKa of saturated fatty acids.

Reported values for the acid dissociation constant (p K a) of the saturated fatty acids show a wide range, depending on their method of measurement. Although the p K a values of the shorter chain saturated fatty acids are generally recognised to be approximately 4.5–5.0, p K a values for the longer chain fatty acids have been reported to be much higher, up to pH 10. It is the purpose of this study to investigate the values of p K a measured using microelectrophoresis for saturated fatty acids with chain lengths between C10 and C18. This returned an average p K a value of 4.0 for these saturated fatty acids. By the method of measurement, this value should be considered as the surface p K a value as opposed to bulk p K a values. The graphs of mobility vs. pH showed isoelectric points between 2 and 3, with the existence of positive surfaces on the particles of fatty acids confirmed. Some examples of the relevance of p K a values for saturated fatty acids in the flotation of non-sulphide minerals have also been given. [ABSTRACT FROM AUTHOR]