20JUL06 and 21JUL06

July 20th. A fresh alumina sample was aged in pH 11.7 solution.  Beginning in a 102 μS/cm KCl solution, the sample was titrated from a pH 10 to pH 3.5 with a nitrogen purge. 

July 21st. An aged alumina sample (7/20) was titrated in a 110 μS/cm KCl solution from pH 10 to pH 3.5 with a nitrogen purge. 

20JUL06 and 21JUL06. This data represents titration of an alumina disc from pH 10 to pH 3.5. As expected the overall pattern corresponds to neutralization of the surface charge. In some cases, between pH 7 and pH 4.5, small increases in pH were noted while zeta potential data were being acquired.  This was accompanied by a decrease in zeta potential as one can see in the figures above. It is not known why, in this range, there is a delayed change in pH after initial mixing.