Chelates formed by a constrained bis(diphenylphosphino)xylene; the crystal structures of [FeCl2(anphos)] and [RhCl(CO)(anphos-monoxide)]

The indan derived diphosphine, cis-1,3-(diphenylphosphino)indan (anphos) is synthesised by the addition of Ph₂P(BH₃)Li to cis-1,3-dibromoindan followed by deprotection with diethylamine. Anphos readily forms the bicyclic chelates [RhCl(CO)(anphos)], [PtCl₂(anphos)], [PtCl(Me)(anphos)] and [FeCl₂(anphos)]. The crystal structures of [FeCl₂(anphos)] and the monoxide complex, [RhCl(CO)(anphosO)] have been determined. Reaction of the diphosphine with [Rh(acac)(CO)₂] under moderate hydroformylation conditions catalysed the formation of 1-heptanal and branched aldehydes from 1-hexene in a ratio of 1.5:1.     

Quinolinium and lutidinium molybdates as reagents for the precipitation of phosphate

The precipitation of phosphate with quinolinium molybdate was studied by means of radioactive tracers, in relation to the excess of reagent, temperature of precipitation, etc. Precipitation is almost quantitative (99.3%) even with a stoichiometric amount of reagent added but an excess helps to minimise the inhibitory effects of certain ions, notably Fe³⁺ ; inhibitory effects are eliminated by digesting the solution for 2 h. Chromium(III) nitrate, nickel(II) nitrate and manganese(II) nitrate have relatively little effect on the precipitation of quinolinium molybdophosphate. Under the conditions required for the quantitative precipitation of phosphorus, arsenic is also quantitatively precipitated.Phosphate can be precipitated as lutidinium molybdophosphate using 2,4-, 2,5- or 2,6-lutidinium molybdate; the reagents are less efficient than quinolinium molybdate but can be used to precipitate phosphate under conditions which leave arsenate in solution.     

A comparative study of the metastable equilibrium solubility behavior of high-crystallinity and low-crystallinity carbonated apatites using pH and solution strontium as independent variables

Using solution strontium and pH as independent variables, the metastable equilibrium solubility (MES) behavior of two carbonated apatite (CAP) samples has been examined, a high-crystallinity CAP (properties expected to be similar to dental enamel) and a low-crystallinity CAP (properties expected to be similar to bone mineral). CAP samples were prepared by precipitation/digestion: (CAP A: high-crystallinity, 1.3 wt% CO3, synthesized at 85 degrees C; CAP B: low-crystallinity, 6.4 wt% CO3, synthesized at 50 degrees C). Baseline MES distributions were determined in a series of 0.1 M acetate buffers containing only calcium and phosphate (no strontium) over a broad range of solution conditions. To assess the influence of strontium, MES profiles were determined in a similar fashion with 20, 40, 60, and 80% of the solution calcium being replaced on an equal molar basis by solution strontium. To determine the correct function governing CAP dissolution, ion activity products (IAPs) were calculated from the compositions of buffer solutions based on the hydroxyapatite template (Ca(10-n)Sr(n)(PO4)6(OH)2 (n = 0-10)) and the calcium/hydroxide deficient hydroxyapatite template (Ca(9-n)Sr(n)(HPO4)(PO4)5OH (n = 0-9)). Findings: (a) for CAP A, at high solution strontium/calcium ratios, the MES profiles were essentially superimposable when the solution IAPs were calculated using the stoichiometry of Ca6Sr4(PO4)6(OH)2 and for CAP B by a stoichiometry of Ca7Sr2(HPO4)(PO4)5OH; (b) for CAP A, at low strontium/calcium ratios, the stoichiometry yielding MES data superpositioning was found to be that of hydroxyapatite and for CAP B, that of calcium/hydroxide deficient hydroxyapatite. When other stoichiometries were assumed, good superpositioning of the data was not possible.     

Analysis of monomeric alkyl- and arylchlorosilanes

The radioisotope carbon-14 was used to study the retention of carbon in the decomposition of alkyl- and arylchlorosilanes by wet methods. Losses by sample volatilisation were overcome by preliminary cooling in dry ice. Fuming sulphuric acid alone or in mixtures with fuming nitric acid was found to be the most effective oxidant of the acids tested. Examination of the carbon-containing silica residues by X-ray powder photography indicated that amorphous carbon was present but there was no evidence of silicon carbide.     

Influence of crystallite microstrain on surface complexes governing the metastable equilibrium solubility behavior of carbonated apatites

This study was on the influence of the mineral phase crystallite microstrain (CM) on the nature of the surface complex (SC) governing the metastable equilibrium solubility (MES) behavior of carbonated apatites (CAPs) in aqueous acidic media (0.10 M acetate buffers, with and without fluoride, 0.50 M ionic strength maintained with NaCl). The MES behavior of a set of four CAPs (synthesized at 85 degrees C by a precipitation method) of increasing CM and therefore of increasing MES (CAP4 > CAP3 > CAP2 > CAP1) was quantified. The following were the findings. For CAP1 and CAP2, the SCs deduced were Ca10(PO4)6(OH)2 and Ca10(PO4)6F2 for the nonfluoride and the fluoride cases, respectively. For CAP3 and CAP4, the SCs deduced were Ca9.5(PO4)6OH or Ca9.5(HPO4)(PO4)5(OH)2 and NaCa9.5(PO4)6F2 for the nonfluoride and the fluoride cases, respectively. These results together with that from an earlier limited study show that the Ca/P ratio of the SC decreases from 1.67 to 1.58 to 1.50 with increasing CM of the CAPs; this relationship inversely correlates with the chemistry of maturation of aqueously precipitated defective apatites. Also the SCs do not appear to exist as a continuous series and only a few SCs may account for the MES behavior over a wide range of CAP preparations.     

Binary chromatographic retention times from perturbations in flowrate and composition

This work is a theoretical and experimental investigation of the binary retention time (t _step) when the disturbance is made to a chromatographic system by adding a small flow of one of the pure components. The established theory is for addition of a pulse: in this case, the retention time (t _pulse) depends on the two binary isotherm gradients, and should be independent of the choice of pulse gas. From the column material balance, the value of t _step also depends on the column pressure drop and perturbation gas—the value of t _step should always be greater for the more-adsorbed component. The theory has been validated from results on the nitrogen–argon–5A zeolite system at 25, 54 and 81 °C. For a 50% mixture at 25 °C with a column pressure drop of 0.1 bar, the values of t _step are 257 and 254 seconds for the nitrogen and argon perturbations. The values of t _step are different because addition of the perturbation flow causes a very small increase in average column pressure (about 0.5 mbar), which causes the binary isotherm gradients to be measured in (slightly) different directions along the isotherm surface. The intention is to determine the value of t _step for the case of a zero change in the average column pressure: experimentally, this would require a column with a zero pressure drop. The material balance shows that t _step for a column with a zero pressure drop is obtained from a simple weighted function of the values of t _step for the two pure-component perturbations. Accurate determination is essential because the “zero pressure drop” values are used to determine binary adsorption isotherms which are, of course, at a fixed pressure.