The rates of reaction and the parameters of activation have been determined for the hydrolysis of 4-nitro-, 3-nitro-, 4-bromo-, 4-methoxy-, 4-methyl-and unsubstituted benzenesulphonyl chlorides m aqueous dioxan containing mole fractions of water between 0 . 9 and 1.00. Further evidence is also found for Vizgert's hypothesis that 2,4,6-trimethylbenzenesulphonyl chlorlde hydrolyses by the SN1 mechanism. I n all other cases the inversion of the effects of substituents which occurs as the water content of the solvent is decreased, the passage of the rate through a maximum incertaincases, and the failure of theHammett free energy correlationcan beaccounted for in terms of 8,2 type mechanisms for hydrolysis in which both bond-making and bond-breaking processes are of importance but are differently biased by the various substituents.

The infra-red spectra of the di-, tri-, and hexahydrates of uranyl nitrate and of anhydrous potassium uranyl nitrate have been recorded. The results differ significantly from those of Gatehouse and Comyns (1958) but do not permit a decision regarding the structure of the complex anions in these compounds.

The solvolysis of aromatic sulphonyl chlorides in methanol-acetone and ethanol-acetone shows only small, irregular effects due to para-substituents because the experimental temperature range is close to the isokinetic temperature. The modification of reaction conditions in SN2 substitutions, so that the isokinetic condition is brought into the experimental temperature range, is discussed. Rates for methanolysis are lower than those for hydrolysis and are about four times the rates for the corresponding ethanolysis reactions.

SwmmclryThe hydrolysis of benzene, p-toluene, p-bromobenzene, and p-nitrobenzene sulphonyl chlorides in 10-60 wt. % water-dioxan and water-acetone has been shown to follow an iSN2 mechanism. The reaction does not show acid catalysis or any " salt " effect. Hammett s equation does not describe fully the effects of substituents on the reaction rate.For solutions in which water has the same molarity, aqueous acetone gives lower rates than aqueous dioxan when the molaritp of water is high but higher rates when the molarity of water is low. Change in the water content of the solvent produces only small changes in the enthalpy of activation except in solutions of low dielectric constant. The reduction in rate as solutions become less aqueous is mainly determined by the entropy of activation becoming more strongly negative.

The amperometric method of Foulk and Bawden when applied to the titration of 0.001N thiosulphate solutions with iodine is shown to be more precise and to have a smaller " blank" than that using starch as indicator. With simple precautions the method has an accuracy of at least 0.1 per cent. over the range pH 1-8, but at higher pH there is serious error due to sulphate formation. The magnitudes of other errors are determined and it is shown that all can be rendered negligible in titrations of milli-normal solutions.