The literature on the solubility of sparingly soluble lead salts in water and in aqueous electrolyte solution was reviewed. Solubility data were compiled and evaluated. Recommended and tentative values of the solubilities are presented. A partial compilation of solubility products and of complex ion formation constants are given. Where possible the solubility product values have been checked for consistency against thermodynamic data from sources other than solubility measurements.

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The reaction of triphenylmethyl radical with oxygen in a solid lattice permeable to oxygen has been studied. The reaction is found to be reversible: PhaC. + O2 Ph3CO0.. At room temperature under atmospheric oxygen pressure very little triphenylmethyl radical exists in equilibrium with the peroxy radical, but at 130" essentially no peroxy radical can be detected. Evacuation at room temperature converts the peroxy radical to triphenylmethyl radical. For the reaction of triphenylmethyl radical with oxygen AH = -9 =t 1 kcal/mole. An energy of activation for the thermal decomposition of triphenylmethylperoxy radical of 10.2 1 kcal/mole is estimated.n solution triphenylmethyl radical reacts with oxygen( 1)Hydrogen atom donors may react with the intermediate peroxy radicals to form triphenylmethyl hydroperoxide.PhaCOO. + RH + Ph3COOH + R.(3)We have found triphenylmethyl radical trapped in polycrystall.ine triphenylacetic acid and triphenylmethyl chloride or bromide reacts reversibly with oxygen to form the triphenylmethylperoxy radical. In the solid lattice the peroxy radical appears to be stable indefinitely at ambient temperatures in samples open to air. In a lattice permeable to oxygen it is possible to determine apparent equilibrium constants as a function of temperature and the heat of reaction for triphenylmethyl radical and oxygen. The activation energy for the decomposition of triphenylperoxy radical has also been estimated from a study of the rate of decomposition of the peroxy radical as a function of temperature.In this study triphenylmethyl radicals were produced by y radiolysis of triphenylmethyl chloride or bromide and triphenylacetic acid. Previous work has shown that y radiolysis of alkyl halides4 and tertiary carboxylic acids5 produces alkyl radicals, e.g.to yield triphenylmethyl peroxide.

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