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OtTuOOi forms. This compound was reported by Ollard (14) and has since been observed by Kasper (8) and the author. In view of the ease with which complex chromichromates form, even in highly acid solution, it is concluded that in chromic dichromate (and, to a lesser extent, in aluminum dichromate) solutions, there exists a progressive hydrolysis in which the two chromate complexes described above form from the dichromate complex. In complete accord with this hypothesis is the low pH at equilibrium of chromic dichromate solutions, as compared to the other compounds studied. No change in pH with time was observed with the perchlorate solutions, confirming the original assumption that they would be free from complex formation.Since anodic oxidation is a result of the potential of oxygen discharge at the anode, which in turn is a function of hydrogen-ion activity, pH would be expected to be an important variable in the control of anodic baths. This has been shown to be the case (1, 17). However, since baths high in chromic acid and aluminum content have been shown to possess proportionately greater hydrogen-ion activity, consideration must be given to this fact in determining the most economical operation of the anodic bath. The laboratory work of Tarr, Darrin, and Tubbs (17) has considered this point thoroughly, and the work has been confirmed by service records of anodic baths in commercial operations (18).

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