No abstract

Adsorption of benzidine on montmorillonite (bentonite) particles suspended in aqueous solutions was studied by measuring the absorbance of the solution at 280 nm before and after mixing the two reactants. Benzidine adsorption decreased with an increase of suspension pH from 7 to 9.3. NaCl and calgon (Na‐hexametaphosphate) decreased the adsorption, the latter being more effective at the equivalent concentration. The interaction between benzidine and montmorillonite was connected to cation exchange processes and was influenced by the specific adsorption of the metaphosphate ion on the crystal edges.

A kinetic study of the formation of benzidine blue on montmorillonite was carried out by measuring the absorbance of the suspension at 580 nm. A preliminary study of the first stage of the reaction was conducted by stopped flow apparatus. The main change in the light absorbance took place during the first minutes of the reaction, but the reaction proceeded at a very slow rate for hours and days. The reaction rate became slower upon increasing the pH and upon addition of calgon (Na‐hexametaphosphate).

X-Band and Q-band esr line widths and intensities of [Cr(H20)e]3+ and [ ( 2 )ß] + in acrylonitrile and polyacrylonitrile were measured as functions of the concentrations of Zn(C104)2-6H20 or Li(C104) added to the monomer and polymer systems. The line width of [Cr(H20)e]3+ incorporated in the polymer was studied as a function of temperature and concentration both in the glassy and rubber-like states. The zero-field splitting parameter was evaluated for [Cr(H20)e]3+ and for [ ( 20)ß]2+ in the polymeric system both above and below the glass transition temperature. It is shown that the electronic relaxation in the polymeric matrix is due to modulation of the zero-field splitting interaction, probably via rotational tumbling of the [Cr(H20)6]3+ ion. A correlation time of ~2 X 10"11 sec at 300°K for the hydrated chromium ion is found both in the glassy and the rubber-like states. In view of the short correlation time scale found and the possibility that ligand exchange mechanisms may operate in the rubberlike state, the similarities of the polymeric system to true liquid solutions are discussed. Evidence from esr and magnetic susceptibility measurements for strong Cr-Cr interaction in the glassy state at low temperature is presented.