Dissolution In Sulphuric Acid Research Articles

Mechanism of Tin Dissolution in Sulphuric Acid

Mechanism of Tin Dissolution in Sulphuric Acid

Stability and open circuit breakdown of the passive oxide film on titanium

Titanium electrodes have been passivated by forming an anodic oxide film in acid solution are known to undergo a spontaneous passive—active transition at open circuit after a delay period that depends on the experimental conditions. In the present work, the reactivation of the electrode has been investigated, and it has been shown that it arises as the result of uniform chemical dissolution of the oxide film. The rate of dissolution, and hence the stability of the oxide, was found to depend on the rate at which the oxide film had been formed as well as on solution composition and temperature. The rate of film dissolution in sulphuric acid showed a first order dependence on proton concentration, but high dissolution rates were also measured in alkaline solution (pH 14). The activation energy for film dissolution in 3.0 mol dm t-3 H 2SO 4 was found to be 63 kJ mol t-1. The reduction of the film under galvanostatic conditions was also investigated, and it was established that simultaneous chemical and electrochemical dissolution occurred uniformly across the electrode surface.

Kinetic aspects of kaolinite acid dissolution: I. Well crystallized mineral

The kinetics and mechanism of kaolinite dissolution in sulphuric acid of several concentrations have been studied. Aluminium extraction was effected at 130, 150 and 170°C and the reaction was carried out in closed reactors operating at pressures of up to 1 MPa. The dissolution curves correspond to the kinetic model of nucleation and growth proposed by Hulbert [J. Br. Ceram. Soc., 6 (1969) 11]. The existence of a compensation effect between the pre-exponential factor of the Arrhenius equation and the apparent activation energy of the process was observed. A mathematical expression for the pre-exponential factor of the Arrhenius equation was found, and was shown to be a function of the acid concentration.

Reactive ion-exchange precipitation procedure for the determination of trace amounts of oxalate

The feasibility of using reactive ion-exchange for the determination of oxalate in aqueous solution has been demonstrated. The procedure consists of pH adjustment of the analyte solution, concentration of oxalate on a lead(II)-loaded cation exchange mini-column in the form of lead oxalate precipitate, reactive elution of oxalate by sulphuric acid dissolution and analysis of the concentrated eluate by permanganate titration. Almost quantitative yields of oxalate are obtained for concentrations typically found in human urine. The procedure represents a simple and reliable technique to concentrate oxalate for determination by classical methods.

The determination of eight elements in human liver tissue by flame atomic absorption spectrometry in sulphuric acid solution

A flame atomic-absorption spectrometric method is detailed for the determination of Ca, Mg, Zn, Fe, Cu, Mn, Rb and Cd in human liver tissue. Metal losses for three alternative sample destruction procedures are discussed; in the recommended procedure, low-temperature ashing in an oxygen plasma is followed by dissolution in sulphuric acid and aspiration into an air—acetylene flame. The necessity of close matching of the K, Na, phosphate and sulphuric acid contents for samples and standards is demonstrated for several elements. The accuracy of the method was established by using NBS SRM Bovine Liver and carefully prepared synthetic standards. The relative standard deviation is typically 5%, although variations in the blood content between portions of liver tissue lead to poorer precision for iron.

Unstable intermediates. Part XC. The radicals AlR3–, SiR3, and PR3+: their electron spin resonance spectra and pyramidal character

Radicals tentatively identified by their e.s.r. spectra as AlR3–(R = alkyl), PH3+, and PR3+ have been prepared by exposure to 60Co γ-rays of the corresponding aluminium and phosphorus alkyls, the latter after dissolution in sulphuric acid. These results, together with those for AlH3–, SiH3, and SiR3 radicals show that the estimated 3p to 3s ratios increase markedly from aluminium to phosphorus, which suggests that these pyramidal radicals flatten in this order, as expected in terms of Pauling's electronegativity theory.This trend is very much more marked for the alkyl derivatives than for the hydrides, the effect of alkyl substitution being to flatten the aluminium derivatives, but to bend those of phosphorus. This is interpreted in terms of hyperconjugation which increases as the positive charge increases.

The anodic dissolution of deformed Mg in H 2SO 4

A study has been made of the effect of the deformation of pure polycrystalline Mg undergoing anodic dissolution in sulphuric acid. In 0·05 and 0·10 N H 2SO 4, deviations from linearity in anodic dissolution rate vs. c.d. plots occur at approximately 18 and 40 mA/cm 3. Examination of the metal surfaces following dissolution reveals a black to grey film (containing dispersed metallic particles) forming above and in the region of these current densities. The maximum points in the positive Δ-c.d. curves for deformed metal anodically dissolving in 0·05 and 0·10 N H 2SO 4 are found at approximately 14 and 38 mA/cm 2 respectively. These results appear to confirm previous studies attributing the maximum and the subsequent decrease in δ (difference effect) primarily to increased anodic disintegration. It would appear that the deformation of the metal does not play a significant role in the mechanism of anodic disintegration.