COLUMN CONFIGURATION AND PERFORMANCE IN FIXED-BED ION EXCHANGE SYSTEMS SIR: We thank Cooney for his discussion of a condition under which the hypothesis of our discussion would not hold. O u r discussion was limited to where the rate law depends only on the concentrations in both phases. Certainly film diffusioncontrolled systems will yield rate laws which will depend upon fluid velocity, since the film thickness will decrease with increasing fluid velocity. However, with regard to independence
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of column utilization on shape, Cooney's discussion of a system with a linear rate law is a special case of our general discussion.
Los Alamos Scientific Laboratory University of California Los Alamos, N . M . Michigan Chemical Corp. Saint Louis, Mich.
W . A . Beyer D. B. James
