The enantiotropic phase transition of antimony(III) oxide

Pure cubic senarmontite and pure orthorhombic valentite were characterised by XRD and infrared absorption spectroscopy, these techniques were also used to characterise heat treated samples. Senarmontite was shown to be the stable low temperature polymorph and valentite the stable high temperature form. The application of classical thermodynamics indicated the transition temperature to be 923K. Valentite was shown to exist below 923K but heat treatment below this temperature caused the metastable valentite to revert to senarmontite. DTA of antimony(III) oxide gave a single sharp endothermic peak at 913K, independent of the crystal modification, thus indicating that melting and phase transition were inseparable thermal events.     

Synthesis and thermal decomposition of antimony(III) oxide hydroxide nitrate

The thermal decomposition of the only known antimony nitrate antimony(III) oxide hydroxide nitrate Sb₄O₄(OH)₂(NO₃)₂, whose synthesis routes were reviewed and optimized was followed by TG-DTA under an argon flow, from room temperature up to 750°C. Chemical analysis (for hydrogen and nitrogen) performed on samples treated at different temperatures showed that an amorphous oxide hydroxide nitrate appeared first at 175°C, and decomposed into an amorphous oxide nitrate above 500°C. Above 700°C, Sb₆O₁₃ and traces of -Sb₂O₄ crystallized.Author to whom all correspondence should be addressed     

Solubility of antimony metal in molten antimony(III) chloride-aluminum chloride and antimony(III) chloride-cesium chloride mixtures

The solubility of antimony metal in molten SbCl₃AlCl₃ and SbCl₃CsCl is reported. Measurements were made at many compositions and temperatures within the following ranges: SbCl₃AlCl₃ system, 1–90 mol% AlCl₃ at 235–430°C; SbCl₃CsCl system, 0.5–25 mol % CsCl at 405°C, 45–80 mol % CsCl at 628°C and 60 mol % CsCl at 562–642°C. The solubility is attributed to the reversible reaction of antimony metal with antimony(III) in the melts to form two types of species with oxidation states below 3+. One type is stabilized in SbCl₃AlCl₃ melts at high pCl (pCl = − log[Cl⁻]) and the other is stabilized in SbCl₃CsCl melts with low pCl. Both types are present in melts with a high concentration of SbCl₃, but it is in such melts that antimony metal has its lowest solubility.     

Determination of antimony(III) with potassium hexacyanoferrate(III)

The determination of antimony(III) with potassium hexacyanoferrate(III) in 5M hydrochloric acid medium and in the presence of 40% v/v acetic acid is described. Ferroin is used as the indicator. Antimony has been determined in tartar emetic, solder and pig lead. Arsenic(III) does not interfere.     

Distinct magnetic dynamic behavior for two polymorphs of the same Dy(III) complex

Two polymorphs of the same Dy(III) complex show distinct slow magnetic relaxation behaviors due to the different local environments of Dy(III) in the crystal. This work represents the first example where the magnetic dynamic property of neutral rare earth complexes could be tuned by growing polymorphic crystals without changing the ligand.     

Alkylenedithiophosphate derivatives of arsenic(III), antimony(III) and bismuth(III)

Tris(alkylenedithiophosphates) of arsenic(III), antimony(III) and bismuth(III),

have been synthesized by the reactions of alkylenedithiophosphoric acids with metal oxides and chlorides and of their ammonium salts with metal chlorides in suitable solvents. Mixed chloride alkylenedithiophosphates of arsenic(III) and antimony(III),

have been obtained by the reactions of metal chlorides with ammonium alkylenedithiophosphates at 1 : 1 and 1 : 2 molar ratios or alternatively by the co-disproportionations reactions of metal chlorides with metal tris(alkylenedithiophosphates) at different (2 : 1 and 1 : 2) molar ratios. These new compounds have been characterized by elemental analyses, molecular weight measurements and spectroscopic (IR, and ¹H and ³¹P NMR) data. Chelated structures with bidentate alkylenedithiophosphate groups have been proposed for all these derivatives.     

Microcolumn sorption of antimony(III) chelate for antimony speciation studies

Selective sorption of the Sb(III) chelate with ammonium pyrrolidine dithiocarbamate (APDC) on a microcolumn packed with C₁₆-bonded silica gel phase was used for the determination of Sb(III) and of total inorganic antimony after reducing Sb(V) to Sb(III) by l-cysteine. A flow injection system composed of a microcolumn connected to the tip of the autosampler was used for preconcentration. The sorbed antimony was directly eluted with ethanol into the graphite furnace and determined by AAS. The detection limit for antimony was significantly lowered to 0.007 μg l⁻¹ in comparison to 1.7 μg l⁻¹ for direct injection GFAAS. This procedure was applied for speciation determinations of inorganic antimony in tap water, snow and urine samples. For the investigation of long-term stability of antimony species a flow injection hydride generation atomic absorption spectrometry with quartz tube atomization (FI HG QT AAS) and GFAAS were used for selective determination of Sb(III) in the presence of Sb(V) and total content of antimony, respectively. Investigations on the stability of antimony in several natural samples spiked with Sb(III) and Sb(V) indicated instability of Sb(III) in tap water and satisfactory stability of inorganic Sb species in the presence of urine matrix.     

Hydrolysis of antimony(III) fluoride complexes

Vibrational and ¹⁷O NMR spectroscopy in combination with quantum chemical calculations are used to investigate the hydrolysis of antimony(III) fluoride complexes. A hydrolytic decomposition of SbF₃ and [SbF₄]^? is accompanied by oligomerization with the formation of edge-and corner-connected dimers ([Sb₂O₂F₄]^2?, [Sb₂OF₈]^4?) and trimers ([Sb₃O₃F₆]^3?, [Sb₃OF₉]^2?) with bridging oxygen atoms. The hydrolysis of [SbF₄]^? is also characterized by the presence in the solution of a discrete cation of [SbF₅]^2? which is least hydrolized. Only a partial isomorphic substitution of fluoride ion by hydroxide one is possible, which is reflected in the composition of K₂Sb(OH)_xF_5?x (x = 0.3) crystals isolated from the fluoride aqueous solution.     

Thiosemicarbazide complexes of antimony(III) halides

Some hitherto unknown complexes of thiosermicarbazide (Htsc) and antimony(III) halides have been synthesized in 1,4-dioxane. The elemental analyses have indicated that these compounds are of the type Sb(CH₅N₃S)Cl₃ and Sb(CH₅N₃S)X₃.C₄H₈O₂, where X = Br or I. The electronic and vibration spectral analyses have shown that Htsc acts as a bidentate ligand in these complexes, linking through sulphur and “the hydrazine terminal nitrogen” to Sb(III).     

Radiochemical determination of traces of arsenic(III) and antimony(III)

Very simple and rapid radiochemical procedures for the determination of traces of arsenic(III) (up to 0.1 μg) and antimony(III) (up to 0.01 μg) have been developed. The method is based on the isotope exchange between labelled metal diethyldithiocarbamate in carbon tetrachloride and an aqueous sample containing the metal to be determined. The selectivity of the method is rather high; in the presence of thiourea most common metals do not interfere with the determination.     

Mixed halide dialkyldithiophosphate derivatives of arsenic(III) and antimony(III)

Mixed chloride dialkyldithiophosphates of arsenic(III) and antimony(III), [(RO)₂PSS]_nMCl_3?n (M = As, Sb; n = 1, 2; R = C₂H₅, n-C₃H₇, i-C₃H₇ and i-C₄H₉) have been synthesized for the first time by the reac metal chlorides with sodium dialkyldithiophosphates or alternatively by co-disproportionation reactions of metal chlorides with metal tris(dialkyldithiophosphates) in different stoichiometric ratios. Mixed halide dialkyl-dithiophosphates of antimony(III) have also been prepared by the cleavage reactions of antimony tris(diisopropyldithiophosphate) with bromine or iodine. Hydrolysis reactions of a few of these compounds have also been studied. The new compounds have been characterized by elemental analyses, molecular weight determinations (cryoscopic) as well as IR and NMR (¹H, ³¹P) data; chelated structures with bidentate dialkyldithiophosphate groups are proposed.     

Two polymorphs of tris(ethylenediamine)cobalt(III) tetrathioantimonate(V)

Details of the structures of two polymorphs of tris(ethylenediamine)cobalt(III) tetrathioantimonate(V), [Co(C₂H₈N₂)₃][SbS₄], are reported. The first polymorph crystallizes in the orthorhombic space group Pna2₁, whereas the second polymorph belongs to the tetragonal space group P4₂bc. Both structures contain octahedral [Co(en)₃]³⁺ cations (en is ethylenediamine) and tetrahedral [SbS₄]³⁻ anions, which are interconnected via various N—H...S hydrogen bonds to form two different types of three‐dimensional network.     

Crystallographic report: Chlorobis(pyrrolinedithiocarbamato)antimony(III)

The X‐ray crystal structure of Sb(S₂CN(CH₂)₄)₂Cl features a five‐coordinate geometry for antimony within a ClS₄ donor set, provides evidence for a stereochemical influence exerted by the lone pair of electrons on antimony, and shows no evidence for molecular aggregation. Copyright © 2003 John Wiley & Sons, Ltd.     

Determination of free acid in antimony(III) and bismuth(III) solutions

A method for the determination of free acid in antimony(III) and bismuth(III) solutions is given. A solution of the disodium salt of EDTA, 2-3 % in excess of the stoichiometric amount, is added to the metal salt solution and titrated with sodium hydroxide solution potentiometrically or visually using a mixed indicator. The error in the method is less than 0.5 %.     

The reaction of neodymium(III) oxide with chromium(III) oxide

The reaction of Nd₂O₃ and Cr₂O₃ in air has been studied in the temperature range 350–950°C. The nature and quantity of products formed was investigated primarily by an analytical scheme developed to permit the determination of the amounts of unreacted Nd₂O₃ and Cr₂O₃ and the amounts of possible products. From 350–600°C the sole product was Nd₂(CrO₄)₃, from 630–840°C the products were Nd₂(CrO₄)₃ and NdCrO₃, and from 880 to 950°C the sole product was NdCrO₃. The variation with temperature of the amounts of products formed at constant reaction time was investigated. The kinetics of the reaction were investigated at the following temperatures, 630, 650, 680, 700, 720 and 760°C. At each temperature, with increasing time the amount of Nd₂(CrO₄)₃ formed increased to a maximum and then decreased whereas the amount of NdCrO₃ formed increased continually. The results together with experiments on the effect of oxygen and argon atmospheres are interpreted as follows. NdCrO₃ is not formed by direct combination of Nd₂O₃ with Cr₂O₃. Instead the reaction of the two oxides produces Nd₂(CrO₄)₃, the thermal decomposition of which then leads to the formation of NdCrO₃. The absence of NdCrO₄ as a reaction product is investigated and discussed as is the absence of NdCrO₃ as a reaction product below 630°C.     

Thermal phase transitions in antimony (III) oxides

Previous reports of the thermal behaviour of antimony trioxide show significant disagreement on the values for the temperatures associated with specific thermal events. In this reappraisal, samples of both polymorphs of Sb₂O₃ (senarmontite and valentinite) have been analysed using X-ray diffraction and simultaneous differential thermal/thermogravimetric analysis techniques. The senarmontite-valentinite phase transition has been observed to occur as a multi-stage event commencing at temperatures as low as 615±3 °C—evidence of oxidation to Sb₂O₄ under inert atmosphere may indicate that the depression is related to surface- or bulk-bound water. Valentinite produced by mechanical milling of senarmontite exhibits the reverse phase transition to senarmontite at a lower than normal temperature (445±3 °C). Oxidation temperatures of 531±4 °C for senarmontite and 410±3 °C for mechanically derived valentinite were also recorded.     

Liquid-liquid extraction of arsenic(III), antimony(III) and bismuth(III) with potassium ethyl xanthate

Summary Methods are described for quantitative extraction of arsenic(III), antimony(III) and bismuth(III) with potassium ethyl xanthate-carbon tetrachloride. The optimum acidity conditions are 0.1–0.2 M hydrochloric acid for arsenic, 1.8–2.5 M hydrochloric acid for antimony and p_H 1.5–4.0 for bismuth. From the organic extracts arsenic and antimony are estimated by conventional iodometric methods while bismuth is determined spectrophotometrically at 400 nm. The effect of acidity, reagent concentration, period of extraction and diverse ions are discussed. The infra-red spectra are also described.

---

Zusammenfassung Verfahren für die Extraktion von As(III), Sb(III) und Bi(III) mit Kaliumäthylxanthat/Tetrachlorkohlenstoff werden beschrieben. Die optimalen Aciditätsbedingungen sind: 0,1–0,2 M HCl für As, 1,8–2,5 M HCl für Sb und p_H 1,5–4,0 für Bi. As und Sb werden nach Entfernung des organischen Lösungsmittels jodometrisch bestimmt; Bi wird im gelb gefärbten Extrakt spektrophotometrisch bei 400 nm bestimmt. Der Einflu\ der Acidität, der Reagenskonzentration, der Schütteldauer und verschiedener Fremdionen auf die Extraktion wird besprochen. Die IR-Spektren der gebildeten Komplexe werden diskutiert.