A study of the mechanism and kinetics of interaction between nepheline powder and ammonium hydrofluoride

Behavior of a skeleton silicate, nepheline, in the reaction of fluorination with ammonium hydrofluoride was studied by means of differential-thermal, X-ray phase, and chemical analyses, IR spectroscopy, and scanning electron microscopy.     

Effect of ligands on the thermolysis of the double complexes [Co(NH3)6]2C2O4[Cu(C2O4)2]2 and [Co(NH3)6]Cl[Cu(C7H4O3)2]

The thermolysis of the complexes [Co(NH₃)₆]₂C₂O₄[Cu(C₂O₄)₂]₂ (I) and [Co(NH₃)₆]Cl[Cu(C₇H₄O₃)₂] (II) in air and hydrogen at 200, 350, and 500°C and the composition and properties of the thermolysis products are considered. The oxidative thermolysis of the complexes yields mixtures of cobalt and copper oxides, including mixed ones. The reductive thermolysis of the complexes yields a Co + Cu bimetallic powder in the case of compound I and a Co + Cu + C powder in the case of compound II. The thermal behavior of the complexes is governed by the nature of the ligand coordinated to the copper atom. The observed data are explicable in terms of the properties of this ligand. The chemistry of the oxidative and reductive thermolysis is discussed. Original Russian Text ? D.P. Domonov, S.I. Pechenyuk, N.L. Mikhailova, A.T. Belyaevskii, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 7, pp. 1104–1110.     

Physicochemical simulation of calcite (dolomite)-FeSO<Subscript>4</Subscript>-H<Subscript>2</Subscript>O open systems

Effect of the chemical composition of carbonate minerals on the precipitation of iron from a Fe(II) sulfate solution was studied.     

Reactions of calcite and dolomite with iron(III) sulfate solutions

Effect of the composition of carbonate minerals on the precipitation of iron from Fe(III) sulfate solutions under conditions of their partial neutralization with calcite and dolomite was studied.     

Phase formation in the systems TiOCl2-H3PO4-MF(HF)-H2O (M = K, Rb, Cs)

From solutions containing 2–17 wt % TiO₂ at the molar ratios M/Ti = 1–4, F/Ti = 2–4, and PO ₄ ^3? /Ti = 0.5–10 under mild conditions, fluoro- and oxo(hydroxo) fluorophosphate titanates were isolated: crystalline M₂TiF₆ (M = K, Rb, Cs) and K₂Ti₂O_2.5F₂PO₄ · 2H₂O, and amorphous K₃Ti₄O(OH)F₇(PO₄)₃ · 5H₂O, Cs₂Ti₃O₂F₇PO₄ · 6H₂O, and CsTi₃O₃F₄PO₄ · 3H₂O. In a mixture with M₂TiF₆ and KCl, phosphate-ion-containing crystalline phases of unidentified composition were detected. The phases were studied by elemental, crystal-optical, X-ray powder diffraction, thermal, IR spectroscopic, and electron microscopic analyses. Annealing fluorophosphate titanates gives a mixture of MTiOPO₄ and TiO₂. All the mentioned alkali metal fluorophosphates contain the tetrahedral ion PO ₄ ^3? and titanium polyhedra with bonds Ti-F and Ti-O; some of them also contain bridging oxygen connecting titanium atoms: Ti-O-Ti; i.e., these substances are polymeric.     

Diagnostics of the Behavior of apatite and its aggregates with sphene in dilute mineral acids

Behavior of monomineral fractions of apatite and sphene and their aggregates in treatment with dilute solutions of hydrochloric and sulfuric acids was studied by electron microscopy, IR spectroscopy, crystal-optical methods, and X-ray and chemical analyses. The manner in which aggregates of apatite and sphene disintegrate was for the first time visualized by electron scanning microscopy. The efficiency of purification of the apatite concentrate to remove apatite with hydrochloric and sulfuric acid solutions was examined.     

Peculiar features of preparation and application of fractionated magnesia-silicate reagent

The properties of magnesia-silicate reagent prepared by thermal activation of serpentinite of varied dispersion were studied. The factors affecting the extraction of copper and nickel with polydispersed metaserpentine were determined     

Electrochemical Oxidation of Galenite in Carbonate Solutions

Linear voltammetry, X-ray phase and differential thermal analyses, diffuse reflection IR Fourier spectroscopy, Raman spectroscopy, and scanning electron microscopy (SEM) were used to study the electrochemical oxidation of galenite in carbonate electrolytes.     

Phase formation in the HfO(NO3)2-H3PO4-CsF(HF)-H2O system

The phase formation in the system HfO(NO₃)₂-H₃PO₄-CsF(HF)-H₂O was studied along the sections at the molar ratios PO ₄ ^3? /Hf = 0.5, 1.5, and 2.0 and RbF:Hf = 1?C5, and also in the presence of HF at CsF: Hf = 1. The initial solutions contained 2?C24 wt % HfO₂. The synthesis was performed at room temperature. The following substances were isolated: crystalline cesium fluorophosphate hafnates CsHf₂F₆PO₄ · 4H₂O, CsHfF₂PO₄ · 0.5H₂O, and CsH₂Hf₂F₂(PO₄)₃ · 2H₂O; X-ray amorphous cesium fluorophosphate hafnate of the average composition Cs₂Hf₃O_1.5F₅(PO₄)₂ · 5H₂O; and X-ray amorphous cesium fluorophosphate nitrate hafnate Cs₅H₄Hf₃F₇(PO₄)_3.66(NO₃)₃ · 5H₂O. The compositions of the amorphous phases should be refined. Cesium fluorophosphate hafnates were obtained for the first time. The compounds were studied by crystal-optical, elemental, X-ray diffraction, IR spectroscopic, and electron microscopic analyses.     

Diffusion Coating of Nickel with Tantalum in Chloride-Fluorotantalate Melts

The effect of temperature and time on the diffusion saturation of nickel with tantalum in molten salt mixture NaCl-14 mol % K₂TaF₇ in the presence of metallic tantalum powder was studied, and characteristics of the obtained diffusion coatings were analyzed.