Kinetics of the precipitation of palladium dimethylglyoximate from homogeneous solution.
The kinetics of formation of palladium dimethylglyoximate in the post-nucleation and pre-nucleation stages, and the effect of palladium on the reaction of biacetyl and hydroxylamine, have been studied.
Co-precipitation of metal dimethylglyoximates generated from biacetyl monoxime or biacetyl and hydroxylamine.
A study has been made of some aspects of the co-precipitation of gold and platinum(II) and (IV) with palladium(II) precipitated from homogeneous solution initially containing biacetyl and hydroxylamine in 0.3M hydrochloric acid. The co-precipitation of nickel(II) with palladium(II) and vice versa from near neutral solutions initially containing biacetyl and hydroxylamine was also explored; the solid is enriched in the minor constituent in both cases. As with biacetyl monoxime-hydroxylamine systems, both nickel(II) and palladium(II) promote formation of dimethylglyoxime from such solutions between pH 7 and 8. Factors leading to this unusual behaviour in co-precipitation are discussed and a qualitative explanation tentatively advanced. The co-precipitation of nickel and palladium(II) is different when biacetyl monoxime solutions are used; the former comes out of solution faster than the latter irrespective of their concentration ratio. This disparity in the reaction rates can be used to separate nickel directly from palladium(II) by precipitation or extraction of the dimethylglyoximate into chloroform.
IONIZATION OF ORGANIC COMPOUNDS IN ACID I. ALIPHATIC KETONES
The changes in the ultraviolet absorption spectra of aliphatic ketones in aqueous sulphuric acid have been followed as the acid strength is increased from 0 to 98%. With increase in strength up to 65% the weak peak at about 270 mμ is shifted to shorter wavelengths by a medium effect. However, with further increase in acid strength the peak disappears altogether because of protonation of the carbonyl group. The pKBH+ values of several ketones have been calculated from the spectrophotometric results to be about −7. The pKBH+ values of cyclic ketones vary systematically with ring size. The significance of the present work to recent studies on the rate of enolization of acetone is discussed.