The pair velocity at -100 mV was initially attractive for several seconds, repulsive for about 5 Prior work showed that colloids in low frequency oscillatory electric fields separate when dispersed in dilute alkaline electrolytes like NaOH and KOH . As a test of the proposed model above, we exposed colloids in 1 mM mixtures of KCl and KOH to pure oscillatory electric fields with no electrochemical reactions. We found that colloids separated in a 400 Hz frequency, 2 V amplitude oscillatory potential when the pH of the electrolyte was > ~10 (Figure ). This is larger than the pH of ~7.