Electrolyte-diffusion of cobalt sulphate in agar gel medium at 25 °C

The diffusion of cobalt sulphate is studied in 1% agar gel over a concentration range of 10^–5 to 0.2M at 25 °C. The experimental values of the diffusion coefficient at various concentrations determined by the zone-diffusion technique are compared with the theoretical values of diffusion coefficinets computed on the basis of Onsager-Fuoss theory. The observed deviations are interpreted in terms of relative contributions of diffusion-enhancing and diffusion-retarding interactions occurring in the water-gel-electrolyte system.     

Diffusion studies of cobalt ions and their salts in agar gel medium: Obstruction effect and gel hydration

The obstruction effect in the electrolyte diffusion of cobalt halides and in tracer diffusion of Co²⁺ ions in the presence of different supporting electrolytes at various concentrations has been studied at 25 °C using the zone diffusion technique. It has been observed that obstruction effect expressed in terms of increases with concentration and is higher for electrolyte diffusion than in tracer diffusion. Further, for a given concentration it is found to decrease with increasing charge density of an anion. These observations are explained on the basis of competitive hydration between ions and agar molecules.     

Diffusion of rose bengal in agar gel: Variation with the concentration of the diffusant and the gel

The diffusion of Rose Bengal¹³¹I in agar gel is studied in the concentration range of 10^–7 to 10^–5M. In addition, effects due to varying the concentration of the gel and temperature are reported.     

Tracer and self-diffusion of rosebengal sodium131I in 1% agar gel medium

Tracer and self-diffusion coefficients for Rosebengal labelled with¹³¹I are determined in agar gel medium at different temperatures and the activation energies for the two processes are determined by zone diffusion technique. The slight difference in tracer and self-diffusion values observed is small enough to be consistent with Hertz's recent theory of linear response of tracer diffusion coefficients in electrolyte and non-electrolyte systems.     

Electrolyte diffusion of ZnCl2 and self-diffusion of Cd2+ ions in agar gel medium at different temperatures

The values of activation energy required for the diffusion of ZnCl₂ and for Cd²⁺ ions in Cd/Ac/₂ are reported in agar gel medium at 5×10^–5 and 0.001M concentration, respectively. These values are compared with the previously reported values in the same systems at different concentrations. The decrease in activation energy with concentration of electrolyte is in agreement with the Wang's model.     

Self-diffusion of Co2+ ions in CoSO4 in agar gel medium: Concentration dependence of obstruction effect and activation energy

The obstruction effect and activation enerqy for the self-diffusion of Co²⁺ ions in CoSO₄ have been computed using the zone-diffusion technique in agar gel medium at five different concentrations of the electrolyte. Both parameters are found to decrease with an increase in electrolyte concentration. The decrease in obstruction effect expressed in terms of is attributed to the competitive hydration between ions and agar molecules in a diffusion system while the decrease in activation energy is explained by considering the changes in the physical properties of the solution with concentration at microscopic level.     

Direct titration of potassium ferricyanide with hydrazine sulphate in presence of zinc sulphate determination of hydrazine

Operative conditions for direct titration of potassium ferricyanide solution with a solution of hydrazine sulphate which contains zinc sulphate are described. The results are comparable with those obtained by the standard iodate procedure. The chief advantages of the present method of estimating hydrazine are (1) titration in slightly acidic medium and (2) no indicator is required. Determination of substituted hydrazines, hydroxylamine and other reducing substances on similar lines is suggested.     

Tracer-diffusion of cobalt ions in sodium and potassium nitrates in agar gel

Tracer-diffusion of Co²⁺ ions is studied in agar gel in the presence of sodium and potassium nitrates at 25°C. The diffusion coefficient values at various electrolyte concentrations are compared with the corresponding theoretical values computed on the basis of Onsager's theory. The deviations from the theory are attributed to the various co-occurring effects in the diffusion medium. The activation energy for the process of diffusion of Co²⁺ ions in presence of above electrolytes is also reported.     

Anomalous spreading with Marangoni flow on agar gel surfaces

We have experimentally observed anomalous spreading of aqueous alcohol solutions on flat and rough fractal agar gel surfaces. On flat agar gel surfaces, extremely fast spreading [θ(D)(t) ∝ t(-0.92)] that differs from Tanner's law [θ(D)(t) ∝ t(-0.3)] was observed when the liquid contained over 9 wt % of 1-propanol in which strong Marangoni flow was observed as a fluctuation on the liquid surface. However, on fractal gel surfaces, different spreading dynamics [θ(D)(t) ∝ t(-0.58)] were observed, although Marangoni flow still occurred. We found the surface-dependent spreading can be discussed in terms of competition between Marangoni flow and the pinning effect due to surface roughness.     

Diffusion constant in gel electrophoresis at high fields

We present new measurements of the diffusion constant D in standard (slab-gel) electrophoresis of DNA at fields up to 10 V/cm. Molecules investigated are bacteriophages: T4 of length 173 kbp and lambda of length 48.5 kbp cut by restriction enzyme HindIII. We show, that D increases with the molecule length for electric field E above 5 V/cm. The results are interpreted within the geometration model.     

Determination of activation energy and the obstruction effect for tracer-diffusion of Co2+ ions in agar gel medium containing transition metal nitrates

Variation of activation energy for tracer-diffusion of Co²⁺ ions in Ni(NO₃)₂, Co(NO₃)₂ and Mn(NO₃)₂ is investigated using 1% agar gel over the temperature range of 25 to 45 °C. The activation energies are obtained by the least square fitting of the diffusion coefficient data obtained at various temperatures through the Arrhenius plots. Further, the extent of obstruction effect by gel macromolecules for Co²⁺ ions in Ni(NO₃)₂, Co(NO₃)₂ and Mn(NO₃)₂ systems at various concentrations of the electrolyte have been determined. The decrease in activation energy is explained by considering the changes in the physical properties of the solution with concentration at microscopic level, while the decrease in obstruction effect expressed in terms of a is accounted for on the basis of competitive hydration between ions and agar molecule.     

Suspension copolymerization of divinylbenzene in a gel medium

A procedure of suspension polymerization and copolymerization in a medium of thermally reversible gels was developed.     

Continuous dialysis of sulphuric acid in the presence of zinc sulphate

Transport of sulphuric acid in the presence of zinc sulphate through the anion-exchange membrane Neosepta-AFN (Astom Corporation, Japan) was studied in a two-compartment counter-current dialyzer with single passes at steady state. The following characteristics were used to characterize the dialysis process: recovery yield of acid, rejection coefficient of salt, and permeability coefficient of the membrane. In case of the H₂SO₄ + ZnSO₄ mixture, permeability of the membrane was quantified by four phenomenological coefficients which are functions of acid and salt concentrations in the feed. They were determined by numerical integration of differential equations describing the concentration profiles of both components in both compartments, which was combined with an optimizing procedure.     

Tracer diffusion of Co2+ ions in agar gel containing multi-electrolyte systems

Tracer diffusion coefficients of cobalt ions have been measured in the supporting medium containing multi-electrolyte systems of alkali bromides. The electrolyte concentration was varied between 10^–6-0.1M at 25°C and the diffusion coefficients were determined by zone-diffusion technique using agar gel medium. The trend in the theoretical values of diffusion coefficients is accounted for by considering the relative contribution of mobility function, ionic strength as well as ion size parameter to the theoretical value in different systems. While the deviations between theoretical and experimental values of diffusion coefficients are explained on the basis of various co-occurring effects in ion-gel-water system.     

Tracer-diffusion of Mn2+ ions in agar gel containing alkali metal chlorides

Prompt gamma-neutron activation analysis, PGNAA, has been used to determine major and minor elements of bituminous coals. Calibration curves for H, C, N, Cl, Si, Ti, Al, Fe, Ca, Na, K, and S were obtained using six coals of different origin. The correlation coefficients are, in general, greater than 0.9 with the exception of C, N, and K. The -peak intensities were corrected for volume hydrogen content and normalised to the source intensity by using the 2615 keV -line from the (n, n) reaction induced in the lead container of the Cf source. Elemental compositions of new coal samples were determined. In spite of the weak neutron source intensity, the comparison between the elemental concentrations measured by PGNAA and by conventional analysis show good agreement except for N, K, S and Ca.     

Effect of autoclaving on zinc oxide in the presence of sulphate ions

The effect of autoclaving a zinc oxide preparation containing SO^2?₄ under 5 and 10 atmospheres is studied by combining X-ray diffraction, differential thermal analysis, thermogravimetry and IR spectroscopy. Textural measurements are also carried out on the parent samples and those produced in the temperature range 200–1000°C.A new phase of a basic carbonates?ulphate, including ammonia in its coordination shell, is observed in the original preparation and having its d distances at 11.060, 8.954 and 2.714 Å. This is transformed to another phase at ～180°C which is also the main phase characterizing the autoclaved samples, and belongs to a basic zinc oxide—sulphate possessing d distances at 7.055, 2.468 and 2.805 Å. Autoclaving the oxide preparation under 10 atm gives hexagonal zinc oxide of high purity and crystallinity at 1000°C. An empirical formula is given for the oxide preparation which describes the different decomposition stages observed. At ～390°C, a reversible reduction process comprising oxygen evolution is observed.Autoclaving increases the area of the parent oxide and at temperatures below 600°C is a function of the structural changes. The autoclaving pressure is insignificant ?600°C.Pore structure analysis showed all the samples to be predominantly mesoporous, coexisting with some micropores except that autoclaved under 5 atm and heated at 250°C which is predominantly microporous. Autoclaving under 5 atm causes narrowing of the pores for products below 600°C. Autoclaving has little effect on the average pore radius ?600°C.Evaluation of the average pore radius from the constructed t-curves for parallel-plate pore idealization is discussed.     

Preparation of an aluminum oxo-hydroxide gel in organic medium

A new method has been developed to prepare aluminum oxohydroxide containing spinnable material and gel. Partial hydrolysis of Al(NO₃)₃·9H₂O in 1-propanol at 78°C produces a spinnable, viscous mixture. The role of the propanol in the hydrolysis proved to be to decrease the polarity of the solvent. In this medium the dissociation of nitric acid is driven back and it decomposes to nitrous gases resulting in the increase of pH in the solution. The conditions have been optimized to obtain the highest hydrolysis degree and to avoid precipitation of basic aluminum nitrate. The resulting optimal temperature is 76–80°C, the time needed is at least 15 h in the case of a laboratory scale preparation. Increasing the ratio of propanol: water and the concentration of Al(III) to the maximum value, leads to the decomposition of 54% of the initial amount NO ₃ ^– ion. By careful drying, the decomposition continues to about 70% and a solid foam comes into existence from the viscous mixture. This foam is able to swell in water, the degree of swelling in mass is about 10. The drying of swollen gel was examined. The spinnable mixture most likely contains polymer chains built up by H-bonds, the foam and the gel probably contain platelets.