Diffuse Reflection Spectra of Acid Clays Colored with Benzidine and Some Other Diamines

Abstract
In order to identify the species responsible for the coloration of acid clay upon the addition of benzidine and related aromatic diamines, the diffuse reflection spectra of colored clays in the presence of water, methanol, and benzene were examined in the range from 4 to 29 kK. The coloration appeared to be due to the oxidation of the diamines held between the silicate sheets to the mono-and di-valent cations. The former cations were found to be in various modes of intermolecular interaction, depending on the kind and amount of the liquid. The lightening of the color upon drying was attributed to the disproportionation of the monovalent cations to the divalent cation and the protonated molecule.

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