Bis(6-mercapto-9-benzylpurine)palladium(II) Table VIII. Rigid Group Angular Parameters Compd , deg a, deg 9, deg (C6Hs),Sna-f 7.1Registry No. (C6Fs)4Sn, 106549-2; (C6Fs)4Ge, 1452-12-6. Supplementary Material Available. A listing of structure factor amplitudes (Tables I and II) will appear following these pages in the microfilm edition of this volume of the journal. Photocopies of the supplementary material from this paper only or microfiche (105 X 148 mm, 24X reduction, negatives) containing all of the supplementary material for the papers in this issue may be obtained from the Journals Department,

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Asymmetric complexes of rhodium(I) with a monothio-/3-diketonate ligand and one of the chelating diolefins norbornadiene, cycloocta-1,5-diene, cyclooctatetraene, duroquinone, or 2,5-di-ieri-butyl-£-benzoquinone have been synthesized and studied by pmr spectroscopy. The compounds show thermally induced intramolecular proton exchange between nonequivalent sites at different rates depending upon the diolefin. In the presence of dimethyl sulfoxide or triphenylarsine the exchange is accelerated. The rate is first order in added nucleophile and a mechanism involving a fluxional five-coordinate intermediate is proposed for this case. In the absence of nucleophiles the rate equation has both firstand second-order terms in complex concentration. Indirect evidence is presented for a five-coordinate intermediate in the absence of added ligand. Kinetic parameters obtained by comparison of observed and computer-simulated pmr spectra are reported.

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Flocculating agents are chemical additives that cause suspended solids to form aggregates called flocs. These agents are used in water treatment, municipal and industrial waste treatment, mineral processing, and papermaking. Flocculating agents are either inorganic salts or water‐soluble organic polymers. They act by shrinking the ionic double layer, or neutralizing the surface charge of suspended particles, or bridging between particles. The type of flocculant used depends on the type of solid–liquid separation being performed. The physical properties and size of the flocs as well as the rate of floc formation are the critical parameters in this process. Flocculants are usually selected by the results of laboratory‐scale experiments. The manner in which the flocculating agent is mixed with the substrate can affect the results. Special analytical methods are used for some flocculating agents. Some agents or impurities in them may present toxicological or environmental problems. The general economic trend is the replacement of inorganic salts with organic polymers, which give improved performance.