The rate of reduction of selenium(VI) to selenium(IV) in hydrochloric acid

The reduction of selenium(VI) to selenium(IV) in 4, 5 and 6M hydrochloric acid was studied at temperatures between 50 and 95 degrees . The reaction rate was determined by measurement of the selenium(IV) formed, by continuous-flow hydride-generation atomic-absorption spectrometry. The most notable feature of the reaction is the strong increase in rate with increasing hydrogen-ion concentration and temperature. The rate increases initially with chloride concentration at constant acidity (mixtures of hydrochloric and perchloric acid) but levels off to an almost constant value at high chloride concentrations.     

Sequential collection of selenium(IV) and selenium(VI) by the use of an anion-exchange resin loaded with bismuthiol-II sulphonic acid

A new ligand-loaded anion-exchange resin has been developed which allows determination of Se(VI) and Se(IV) in mixtures of the two. The ligand is a sulphonic acid derivative of bismuthiol-II.     

An efficient protocol for the preparation of MOM ethers and their deprotection using zirconium(IV) chloride

An efficient protocol for the preparation of MOM ethers from alcohols and formaldehyde dimethyl acetal (DMFA) using ZrCl₄ (10 mol %) at room temperature under solvent free conditions has been developed. Similarly, the same Lewis acid, ZrCl₄ (50 mol %), in isopropanol at reflux was utilised for the deprotection of MOM ethers.     

The preparation of potassium octacyanotungstate(IV) dihydrate

K₄W(CN)₈ · 2 H₂O was prepared by the reduction of WO (in potassium cyanide medium) by KBH₄. The reduction proceeds on the slow, drop-by-drop addition of concentrated acetic acid. The synthesis is simple and efficient because the reduction and complexation are accomplished at the same time.     

Determination of selenium(IV) and tellurium(IV) by differential pulse polarography

Differential pulse polarographic methods for the determination of selenium(IV) and tellurium(IV) in nitric acid medium are described. The peak current is maximal when 0.25M nitric acid medium is used, the DPP peaks for Se(IV) and Te(IV) being at -0.54 and -0.8 V vs. Ag/AgCl respectively. The peak current is a linear function of selenium concentration over three ranges, 5.1 x 10(-6)-1.3 x 10(-5), 1.27 x 10(-5)-1.27 x 10(-4) and 1.27 x 10(-4)-7.60 x 10(-4)M Se(IV), with different slopes. The plot for Te(IV) is linear over the range 0.78 x 10(-6)-9.40 x 10(-5)M.     

Sterically demanding bis(2-silylindenyl)zirconium(IV) dichlorides as polymerisation catalyst precursors

A set of different 1- and 2-silyl-substituted zirconocene dichloride/MAO catalyst systems was investigated with respect to their performance in ethene/1-hexene copolymerisations. In-depth studies of bis(2-dimethylsilylindenyl) zirconium(IV) dichloride ( 1 ) revealed a multi-site behaviour, illustrating sensitivity to the reaction temperature and the comonomer mole fraction. Surprisingly, an upper limit is observed for the latter, leading to complete catalyst inhibition. Analysis of the chain termination processes implies the possibility of a predominant, although in general less favourable, β-hydride elimination route under certain polymerisation conditions.     

Interaction of tin (IV) chloride with sulfolane and between tin (IV) chloride and lithium chloride in sulfolane solution

Tin (IV) chloride reacts with sulfolane (S) to form a cis-octahedral adduct SnCl₄·S₂. Solutions of lithium chloride and tin (IV) chloride in sulfolane contain the complex ions SnCl ₅ ^– and SnCl ₆ ^2– at 11 and 21 mole ratios of constituents, respectively. The complexes are characterized by conductimetry and by Mössbauer, IR, and Raman spectroscopy.     

Pentacoordinated Tin(IV) chloride complexes

Preparation and I.R. spectra of tin(IV) chloride complexes with acridine and piperazine have been described and their structures have been suggested.     

Sulphoxide complexes of oxovanadium(IV) chloride and oxovanadium(IV) sulphate

Summary Ten complexes of VOCl₂ and VOSO₄ with several aliphatic and aromatic sulphoxides were prepared and studied systematically. Three were reported previously, and we have extended studies of them. The isolated complexes were characterized by elemental analysis, conductivity, thermal analysis, i.r. and electronic spectroscopy.     

Fabrics and papers modified with analytical reagents for the test determination of selenium(IV) and tellurium(IV)

It is shown that Malachite Green and Crystal Violet immobilized on viscose fabrics can be used as reagents for the rapid determination of selenium(IV) and tellurium(IV). Selenium is determine by the color intensity of ion associates formed by the reagents with the triiodide ion formed upon the reduction of selenium(IV) with potassium iodide and tellurium, by the color intensity of reagent ion associates with telluromolybdic heteropoly acid. The analytical ranges for selenium and tellurium(IV) were 0.005–0.5 and 0.01–0.1 mg/L upon passing 20 and 100 mL of a test solution through the indicator matrix, respectively. The duration of analysis does not exceed 15–20 min. The relative standard deviation is 50%. Test strips were proposed for determining 0.1–100 mg/L selenium(IV) and 1–1000 mg/L tellurium(IV) by the length of the colored zone. The determination of selenium(IV) is based on the oxidation of 4-nitrophenylgydrazine to its diazonium salt and salt interaction with naphthylamine chemically immobilized on paper with the formation of a red azo compound. The determination of tellurium(IV) is based on its reaction with Bismuthol II immobilized on a paper.     

The reactions of some organotin(IV) chlorides with antimony(V) chloride and boron(III) chloride

The reactions of the organotin chlorides R_nSnCl_4?n(R = Me or Ph; ? n ? 4) with the Lewis acids SbCl₅ and BCl₃ have been investigated by ¹¹⁹Sn and (where appropriate) ¹¹B NMR spectroscopy. The results show that transfer of organo-groups to antimony or boron usually takes place rather than chloride abstraction to give cationic tin(IV) species, and this process is more facile for phenyl than methyl groups. These conclusions have been confirmed in some instances by isolation of the non-volatile reaction products.     

The photodegradation of poly(vinyl chloride) films—IV

The concentration of residual tetrahydrofuran in cast poly(vinyl chloride) films has been varied. It is shown that the amount of tetrahydrofuran present does not affect the extent of degradation but that it does affect the relative concentration of the conjugated polyenes produced. A shift towards shorter polyenes is observed with increasing concentration of residual solvent; this effect is attributed to its ability to act as a plasticizer.     

Ceramic composite electrode for the determination of selenium(IV) by stripping voltammetry

A ceramic composite electrode for the determination of selenium(IV) was manufactured using solgel and screen-printing technologies. This electrode exhibits a higher sensitivity and selectivity in comparison with the other studied carbon-containing electrodes. The effect of the type and amount of graphite powder, modifier, catalyst, and pore-forming agent on the properties of the ceramic composite electrode was investigated. It was found that an increase in the pore size in the electrode reduced the selectivity of selenium(IV) determination. The calibration plot was linear over the range 0.1–20 μg/L at an accumulation time of 10 s. The relative standard deviation for the determination of 1.0 and 0.05 μg/L of selenium(IV) (n = 5) was 3% and 8%, respectively. The detection limit of selenium(IV) was 0.02 μg/L at an accumulation time of 90 s. The results of selenium(IV) determination in natural and mineral waters are presented.