All electrophoretic measurements were performed in a 0.01 M
NaCl indifferent electrolyte solution using a Zeta Meter model 3.0+.
A freshly ground quartz, or smithsonite sample of 0.05 g, was conditioned
with given reagents at different pH in a 500 ml beaker and
mixed for 10 min. The coarse mineral particles were then allowed
to settle and the supernatant containing the fine particles was taken
for zeta potential measurements at room temperature. The solution
was transferred from the conditioning vessel to the electrophoretic
unit through a peristaltic pump unit to prevent the solution being
exposed to air. The results presented in this paper are the average
of three such independent measurements with a maximum standard
deviation of ±1.5 mV.