Showing papers on "Sodium metavanadate published in 1973"
TL;DR: In this article, the reactions of various sodium oxo-compounds with vanadium pentoxide and sodium metavanadate are described by means of thermal gravimetric analysis, differential thermal analysis, and powder X-ray crystallography.
Abstract: The reactions of various sodium oxo-compounds with vanadium pentoxide and sodium metavanadate are described. Products of reaction are characterised by means of thermal gravimetric analysis, differential thermal analysis, and powder X-ray crystallography. Sodium metavanadate. NaVO3, and sodium pyrovanadate, Na4V2O7, are found to possess two temperature-dependent structural modifications, whilst four structural modifications of the orthovanadate, Na3VO4, are obtained depending on the method of preparation.
15 citations
TL;DR: Spectrophotometric absorbance measurements on sodium metavanadate solutions in the region 240-300 nm were made at 10°, 25°, and 40°C on: (1) a series of solutions 2.46 x 10-5M in vanadium and covering the pH range 7-9; and (2) an equilibrium solution at constant pH and covering a concentration range from 4x10-5 to 1.2×10-2M as discussed by the authors.
Abstract: Spectrophotometric absorbance measurements on sodium metavanadate solutions in the region 240-300 nm were made at 10°, 25°, and 40°C on: (1) a series of solutions 2.46 x 10-5M in vanadium and covering the pH range 7-9; and (2) a series of solutions at constant pH and covering the concentration range from 4x10-5 to 1.2x10-2M. All solutions contained 3.0M NaClO4 and 0.10M Tris buffer. From these data were computed the extinction coefficients of HVO42-, H2VO4-, and (VO3-), as well as the pKa of H2VO4- (7.62±0.07). Metavanadate is probably a mixture of V3O93- and V4O124- under the conditions of the experiment. Upper limits on the formation constants at 25° are K3 = 10.8±0.5x106 12 mol-2 and K4 = 73±7x 10913 mol-3. The temperature dependence of the data gives for the enthalpy of polymerization, ΔH° = -21±2 kJ mol-1 H2VO4-.
13 citations
TL;DR: In this paper, the reactions of five vanadium compounds of oxidation states (IV) and (V) in nitrite melts have been studied, and it was shown that vanadyl(IV) sulphate and vanadium dioxide are initially oxidised to metavanadate, while vanadium pentoxide initially reacts to give both metvanadate and metavanadi dioxide, the latter then reacting further to form metavanade.
9 citations
01 Jan 1973
TL;DR: In this paper, the optical density (D) of solutions of V(V) was estimated according to the change in the optical densities of solutions in a time and the reaction rate in more concentrated solutions was followed according to changes in the concentration of VV and the eomplexone with time.
Abstract: tion of V(V) we used NaVe 3 �9 2H20 , recrystallized twice from water. DTPA and EDTA were used in the form of dilute solutions of the sodium salts of these acids. Solutions of the complexones and V(V) were prepared according ~:o an exact weighed sample. The concentration of sodium metavanadate was determined 537 oxidimetric titration; the excess Mohr's salt added to the solution of NaVO~ was titrated with K2Cr2OT; phenylanthranilic acid was used as the indicator. The concentration of DTPA and EDTA in solutions was determined by complexometric titration [7]. To create a constant ionic strength (p -- 1.0 M), sodium metavanadate and the complexones were dissolved in a 1 M solution of NaCIO 4. The |dneties of the oxidation of EDTA was studied at 98 ~ DTPA at 50 ~ The mixture of reagents was exposed in a constant temperature chamber for a definite time, then the redox equilibrium was "frozen" by rapid cooling of the reaction mixture with ice water. The reaction rate was estimated according to the change in the optical density (D) of solutions of V(V) in a time (~-). The reaction rate in more concentrated solutions was followed according to the change in the concentration of V(V) and the eomplexone with time. The acidity of the solutions was monitored with an LPU-01 potentiometer.
1 citations
TL;DR: In this paper, the reactions of various sodium oxo-compounds with vanadium pentoxide and sodium metavanadate are described by means of thermal gravimetric analysis, differential thermal analysis, and powder X-ray crystallography.
Abstract: The reactions of various sodium oxo-compounds with vanadium pentoxide and sodium metavanadate are described. Products of reaction are characterised by means of thermal gravimetric analysis, differential thermal analysis, and powder X-ray crystallography. Sodium metavanadate. NaVO3, and sodium pyrovanadate, Na4V2O7, are found to possess two temperature-dependent structural modifications, whilst four structural modifications of the orthovanadate, Na3VO4, are obtained depending on the method of preparation.