Jan Balej

Kinetics of the decomposition of hydrogen peroxide in alkaline solutions

Hydrogen peroxide decomposition in 1–5 mol dm–3 KOH and 1–2 mol dm–3 NaOH solutions is a first-order reaction with respect to undissociated hydrogen peroxide. The decomposition is catalysed by compounds of heavy metals (Fe, Cu) present as trace impurities in these solutions and is first order with respect to them. The hydroxyl ion concentration exerts a significant effect on the decomposition rate, which has been explained by its influence on the activity of catalysing species having colloidal character, which are probably the active sites for the decomposition.

Thermodynamics of reactions during the electrosynthesis of peroxodisulphates

Abstract On the basis of recent more exact values of chemical thermodynamic properties of individual substances the standard electrode potentials and equilibrium constants of various electrode and chemical reactions carried out during the electrosynthesis of peroxodisulphates were recalculated. In some cases, quite remarkable differences in comparison to the values according to Latimers data have been obtained. For the first time the standard potential of the anodic discharge of Caros acid as well as the equilibrium constant of the hydrolysis of peroxodisulphate to peroxomonosulphate ions have been evaluated.

Energy balance of D2O electrolysis with a palladium cathode: Part I. Theoretical relations

On the basis of reliable thermochemical data, the relations for the calculation of the thermoneutral voltage, Etn, of the D2O electrolysis from an approx. 0.1 M LiOD+D2O solution with a Pd cathode with PdDn formation have been derived for stationary and non-stationary courses of electrolysis, as a function of reaction temperature, total pressure and current efficiencies of 02(g) and D2(g) evolution. Due to the lack of thermochemical data for PdDn formation with n > 0.8, the accuracy of the calculated thermoneutral voltage with PdDn formation under non-stationary conditions is lower than for the case of stationary electrolysis.

Electrochemical properties of tungsten bronzes—I. Hydrogen absorption in sodium tungsten bronzes

Abstract Cathodic evolution of hydrogen on the electrodes from sodium tungsten bronzes was studied. Great dependence of cd on time and prepolarization of the electrode is caused by absorption of atomic hydrogen in the electrode; this process is controlled by hydrogen diffusion in bronze. Mechanism of hydrogen evolution in sulphuric acid solutions was proposed on the basis of polarization curves, the dependence of overvoltage on the activity of hydrogen ion and anodic chronopotentiometric curves. The rate of hydrogen evolution is controlled by the reaction of electrochemical desorption of atomic hydrogen, the adsorption of which is fast and obeys Langmuir isotherm. Exchange cd of hydrogen evolution is of the order 10 −7 to 10 −6 A cm −2 and increases with the increase of sodium content in the bronze.

Influence of mercury on hydrogen overvoltage on solid metal electrodes—I. Stationary polarization curves of hydrogen deposition on pure and poisoned electrodes

Abstract Mercury deposited in amounts of the order of a few monolayers on Pt, Fe, Ni and Co raises the overvoltage of hydrogen evolution in alkaline solution. On Cr it decreases the overvoltage and on Mo it has little influence, but these metals corrode in alkali.

Standard potential of sodium amalgam at 25°C

Abstract From a set of critically selected literary data on the emf s of concentration cells consisting of sodium metal and sodium amalgam in a sodium salt non-aqueous electrolyte a value of E O Na(Hg)/Na + = −1.9558 4 V was calculated for the standard equilibrium potential of diluted liquid sodium amalgam at 25°C. The standard state of amalgam was derived from an amalgam at infinite dilution where f Na → 1.0 for x Na → 0. The activity coefficient of sodium in the amalgam at an arbitrary composition, corresponding to this standard state, is obtained from the expression lg f Na(Hg) = 16.393 x Na .

Composition of aqueous solutions of ammonium sulphate and sulphuric acid

Concentrations of SO2–4 and HSO–4 anions in aqueous solutions of ammonium sulphate and sulphuric acid have been determined by means of Raman spectroscopy. The molar ratio P0=mH2SO4/m(NH4)2SO4 and the total molality mT were in the range 1.0–2.5 and 3.38–18.21 mol kg–1, respectively. The results obtained have been used to establish the dependences of the stoichiometric dissociation quotient Qm=mH+mSO–4/mHSO–4 and of the fraction α of total sulphate on the molar ratio P0 and the total molality mT of the solution at 20 °C.

Solubility in the system NiCl2–ZnCl2–H3BO3–H2O at 15, 20 and 25 °C

Solubility in the system NiCl2–ZnCl2–H3BO3–H2O for a limited concentration range of ZnCl2(up to 13.5 wt %) has been investigated at 15, 20 and 25 °C. In the ternary system NiCl2–ZnCl2–H2O no formation of solid solutions takes place, contrary to similar systems of sulphates or nitrates of both cations: only nickel chloride hexahydrate, NiCl2· 6H2O, has been found as the coexisting solid phase in the mentioned concetration and temperature range. The ternary system NiCl2–H3BO3–H2O belongs to a simple system in which each of both components crystallizes in a pure from form mixed saturated solutions, with the exception of eutonic solutions, with which both solid components coexist together. In the quaternary system, the solubility of NiCl2 decreases slightly with increasing content of ZnCl2 and H3BO3. Similar trends have been observed for the solubility of H3BO3 dependent on the content of NiCl2 or ZnCl2, respectively. The solubility dependence of the crystallizing component on the content of other components (in wt % and mol kg–1) and on the temperature have been expressed numerically.

Theoretical background of brine electrolysis: the standard emf of the cell Pt|Cl2|NaCl|Na(Hg) at elevated temperatures

Abstract On the basis of recent determinations of standard electrode potentials of chlorine electrode and of the concentration cell NaNa(Hg), and taking into account the temperature dependence of molal heats of individual reaction components, the values of reversible voltage of NaCl electrolysis in an amalgam electrolyser under standard as well as non-standard reaction conditions were calculated for the temperature region 25–100°C. Simultaneously, standard electrode potentials of sodium and sodium—amalgam in aqueous solutions in the temperature range 25–97.83°C (up to the melting point of sodium) were also calculated.

Relation between potential of binary liquid alloys and composition of intermetallic compounds contained therein

Abstract For systems of binary liquid alloys for which the existence of defined intermetallic compounds in the solid state had been proved, a theoretical expression was derived for the relation between the electrode potential and the composition of liquid alloys under the assumption that intermetallic compounds can exist even in liquid alloys. It was further shown that, for limited conditions, such a relation is of the same form as that obtained for binary systems on the basis of the theory of regular solutions if no formation of intermetallic compounds is considered. These results lead to the conclusion that the validity of the relation based on the theory of regular solutions of simple binary systems is far from being a proof that the existence of intermetallic compounds in such liquid binary alloys is impossible.