D.F.C. Morris

Application of solvent extraction to the refining of precious metals IV. Practical and structural aspects of the separation of rhodium, palladium, iridium and platinum with organic sulphoxides

Abstract Distribution isotherms have been determined radiometrically for the extraction of Pd II , Pt IV , Rh III and Ir III,IV from aqueous HCl solutions by organic sulphoxides in 1,1,2-trichloroethane (TCE). Partition measurements were also made using two different dialkyl sulphides in TCE. A practical scheme for the separation of the precious metals involving di- n -heptyl sulphoxide (DHSO) is proposed. The nature of the metal-ion species participating in the extraction systems and the chemical bonding in such species have been investigated using physical, spectroscopic, and theoretical methods.

Zinc chloride and zinc bromide complexes—IV. Stability constants

Abstract Stability constants for the formation of zinc chloride and zinc bromide complexes have been determined using a solvent extraction method at an ionic strength of 1·00 M. Enthalpy and entropy changes accompanying the formation of the different complexes at 25°C have been evaluated.

A study of chromium(III) chloride complexes using chromium-51 as tracer☆

Abstract Evidence for the existence of the outer-sphere ion-pair Cr(H 2 O) 6 3+ .Cl − in aqueous solutions containing chromium(III) and chloride is presented. The stability constant for the formation of the species has been determined at different fixed temperatures for solutions of ionic strength 1 M maintained with perchloric acid. The formation constant at 40° of the inner-sphere complex Cr(H 2 O) 5 Cl 2+ has also been derived. A solvent extraction method and 51 Cr as tracer were used for the measurements.

Extraction of anions by a liquid cation-exchanger☆

Abstract The distribution ratio has been measured for the extraction of tracer quantities of a number of metals from aqueous solutions of HX or LiX (X = Cl, Br) by the liquid cation-exchangers 0·1 M dinonyl naphthalene sulphonic acid and 0·1 M lithium dinonyl naphthalene sulphonate in n-heptane. In several cases at high halide concentrations the partition behaviour shows marked deviation from that to be expected from the cation exchange process. The effect arises in instances where the metal is very strongly taken up by anion exchangers and anomalous extraction is always greater from lithium halide solution than from the corresponding aqueous halogen hydracid. The dinonyl naphthalene sulphonates occur in the organic layers in micellar form and the composition of such aggregates containing invaded supporting electrolyte and water has been ascertained. Spectrophotometric and stoichiometric measurements on lithium dinonyl naphthalene sulphonate in n-heptane extracts of macro-quantities of metals M(III) or M(II) from concentrated lithium halide solutions have demonstrated the presence of anionic metal halide complexes in organic phases. Slope-analysis of partition data obtained with the metals present at trace concentration gives results in agreement with these conclusions, and the anomalous extraction behaviour can be formulated as involving equivalent exchange of a complex metal-halide anion with invaded halide associated with micelles in the organic medium.

Linear free energy relationships in the thiophene series. Part 3. A kinetic study of chlorine-isotopic exchange between lithium chloride and some 2-chloro-3-nitro-5-X-thiophenes

The rate constants for the chlorine-isotopic exchange between lithium chloride-36 and some 2-chloro-3-nitro-5-X-thiophenes (la—g) have been measured in sulpholane solution. The results obtained give a good Hammett correlation (in the range 323–373 K; calculated ρ 5.55—4.68), indicating that the charge developed in the transition state is strongly affected by the electronic effects of substituents. In order to study the effect of solvent on reactivity, the rates of 2-chloro-3,5-dinitrothiophene (lg) have also been measured in acetone, methanol, and propan-2-ol solutions. A comparison has been made between thiophene and benzene derivatives and the MNDO technique has been used to provide a theoretical model of the exchange reaction.

Acetyl exchange between acetylmesitylene and acetyl chloride under Friedel–Crafts conditions

The kinetics of acetyl exchange, catalysed by aluminium chloride, between acetylmesitylene and acetyl chloride have been determined for homogeneous solutions in nitromethane, and provide the first direct proof of reversibility in a classical Friedel–Crafts acylation.

Formation of scandium(III) chlorate and scandium(III) bromate complexes in aqueous solution

Abstract Stoichometric stability constants for the formation of scandium(III) chlorate and scandium(III) bromate complexes have been measured at several temperatures by using a liquid cation exchanger. Relations between ligational enthalpy and entropy changes are discussed in connexion with the formation of outer-sphere ion pairs and inner-sphere complexes.

Acetyl exchange between acetyl chloride and sterically hindered aryl ketones under Friedel–Crafts conditions

The kinetics of acetyl exchange between acetylmesitylene, or acetyldurene, and 14C-labelled acetyl chloride have been measured in nitromethane solution in the presence of aluminium chloride. Mechanistic studies using acetyl[3,5-2H2]mesitylene as substrate show conclusively that acetyl exchange proceeds, not by acylation–deacylation or deacylation–acylation, but via a synchronous reaction involving an ipso-complex. Theoretical calculations (MNDO) indicate that of three possible synchronous pathways, two are energetically feasible.

Outer-sphere and inner-sphere interactions in the formation of metal-ion nitrate complexes

A liquid—liquid distribution method using radioactive tracers has been employed to determine stoichiometric stability constants for the formation of mononitrato-complexes of MnII and CdII. In each system only quite weak complexing is found. With Mn2+-NO-3 the interaction between the two ions is of outer-sphere kind, whereas in the case of Cd2+-NO-3 both outer and inner sphere species appear to be formed. These conclusions are compatible with Raman spectral evidence.

The occurrence of beryllium in fluorite

Abstract The occurrence of significant traces of beryllium in fluorite would appear to be unlikely on crystallographic grounds, yet Sainsbury has reported as much as 0.01 per cent Be in the mineral from the Lost River area, Alaska. In the present paper a spectrochemical method and a radiochemical isotope dilution procedure for the determination of beryllium in fluorite are described. These techniques have been used to analyze some sixty specimens of fluorite from arbitrarily selected localities. The results indicate little tendency for beryllium to concentrate in fluorite, although samples from areas particularly rich in beryllium were not examined. A study of the coprecipitation of beryllium with calcium fluoride shows that the carrying of the trace element up to a level of ~900 ppm resembles isomorphous replacement. This observation is discussed.