ACID AND BASE BINDING CAPACITIES AND VISCOSITY RELATIONS IN CERTAIN WHITEWARE CLAYS *

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Abstract
In studying the relationships between the chemical and the physical behavior of clay slips, correlations otherwise obscured are brought out if the clay is first carefully purified. Electrodialysis seems to be an effective method of removing interfering adsorbed electrolyte from clay in preparing it for such investigations.Electrodialyzed samples of several whiteware clays in wide use in the ceramic industry were found to behave chemically as weak acids and bases. The amount of Na‐OH necessary to neutralize the “acids” coincided with the smallest amount sufficient to produce the minimum viscosity in suspensions of these clays.The pH of exchange neutrality of each clay agreed closely with a maximum in its pH‐viscosity curve. At this point, the addition either of HCl or NaOH reduced the viscosity, although not equally. As further amounts of NaOH were added, two effects were recognized. Some clays continued to become more fluid until complete deflocculation, while other clays passed first through a range of concentration in which NaOH caused increasing Viscosity. Changes in viscosity were observed also in suspensions with increasing concentrations of HCl. A theory for these effects is presented.

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