Optimum domains for the removal of color during the coagulation process were studied in a series of jar tests and diagrammed as an aid to the design and operation of water treatment plants. The mechanisms for the removal of color associated with humic acids seem to be closely related to those associated with the removal of turbidity.

A substance indentified as polyphenyl1,2 has been obtained by the condensation of paradichlorobenzene using the Wurtz‐Fittig reaction. The viscosity behavior of polyphenyl is unusual. The curves obtained by plotting specific viscosity divided by concentration versus concentration pass through a maximum at very low concentrations, reaching a constant value at a concentration of about one percent. In the region of the maximum, the specific viscosity divided by the concentration is dependent on the rate of shear, increasing with decreasing rate of shear.

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Board's Division of Banking Supervision and Regulation, prepared this article. Terrill Garrison provided research assistance. 1. See box ''Classes of Derivatives'' for an explanation of the different types of derivatives and the ways they are used.

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