5JUL06, 6JUL06 & 7JUL06

July 5th.  A polished sapphire sample was pre-treated in pH 11 solution (30 minutes)and used in 1mM KCl solution.  The solution was titrated from pH 10 to pH 3.5. 

July 6th.  A sapphire sample was sonicated after polishing.  It was then pre-treated in pH 11 solution (30 minutes) and used in 1 mM KCl solution.  The solution was titrated from pH 10 to pH 3.5.

July 7th.  A sapphire sample was sonicated after polishing.  It was then pre-treated in pH 11 solution (30 minutes) and used in 1 mM KCl solution.  The solution was titrated from pH 10 to pH 3.5.

The purpose of sonication was to remove remaining alumina particles. Sonication was retained as a step in pre-treatment, but it had no or minimal effect on the titration data. Note that the isoelectric point is around a pH of 4, while for the mica surface, which has a silicate surface unless aluminum species have been dissolved at low pH and re-deposited, the isoelectric point is below 3. Comparative data can be found in [Franks03].

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