• P M Barve

      Articles written in Proceedings – Section A

    • Condition of sparingly soluble substances in gels - Part I. Silver chromate in gelatine

      R R Khanolkar P M Barve B N Desai

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      Changes in the conductivity and colour of silver chromate in gelatine solution have been studied. It is observed that by suitable adjustment of the (i) temperature of the experiments, (ii) pH of gelatine, (iii) concentration of the reactants (AgNO3 and K2CrO4) and (iv) amount of gelatine, the conductivity may (a) not decrease at all till the colour remains yellow, (b) decrease sometime after the colour change or (c) not change at all in spite of the colour change.

      In the end we would like to mention that our preliminary experiments on the precipitation of lead iodide in agar have shown that the (a) temperature ture at which the experiments are carried out, (b) pH of agar, (c) amount of agar and (d) concentration of the reactants [Pb (NO3]2 and KI) have a very marked influence upon the times when the colour change and decrease in conductivity take place7 as in the case of precipitation of silver chromate in gelatine.

    • Importance of dialysis in the study of colloids - Part III. Colloidal Prussian blue

      G F Mankodi P M Barve B N Desal

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      The cat. speed of colloidal prussian blue (prepared by peptisation with oxalic acid) with the progress of dialysis first increases and then decreases, while the stability as determined by flocculation values with KC1 continuously decreases. The cat. speed on dilution first increases and then decreases in some case while it continuously decreases in others; the stability on dilution is found to decrease continuously in all the cases. These results of dialysis and dilution are exactly similar to those obtained with colloidal ferric and thorium hydroxide investigated by Desai and co-workers.

      The changes in the cat. speed and viscosity under different conditions show that neither the view of Dhar nor of v. Smoluchowski can individually explain the results.

      The idea of critical potential is supported.

      The cat. speed of the sol decreases on ageing and exposure to sunlight, sols dialysed for short periods even coagulating when exposed to sunlight for a couple of minutes.

    • Importance of dialysis in the study of colloids - Part IV. Colloidal arsenious sulphide

      C B Joshi P M Barve B N Desai

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    • Adsorption of naphthols in the presence of different electrolytes and peptising agents and at different temperatures

      J A Nabar P M Barve A M Patel B N Desai

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      Adsorption of some dyestuffs of the Naphthol AS series by cotton fibre has been studied in the presence of alcohol, sodium hydroxide, sodium chloride, sodium sulphate, sodium phosphate, soap, gum tragacanth and agar-agar and at different temperatures to understand the mechanism of the process of dyeing.

      It is observed that adsorption of the dyestuffs decreases with increasing amount of alcohol, gum tragacanth and agar-agar, while it first increases, reaches a maximum and then decreases on adding increasing amounts of sodium hydroxide, sodium chloride, sodium sulphate, sodium phosphate and soap solutions. Regarding the effect of temperature on adsorption, it is found that (1) the rate of adsorption is greater at higher than at lower temperatures, (2) the equilibrium adsorption increases with the rise of temperature, and (3) the amount of increase of adsorption for a particular range of temperature is greater at lower than at higher temperatures.

      The results obtained become easily intelligible if it is assumed that the dye particles exist in colloidal condition and the process of dyeing is interpreted from that point of view.

    • Importance of dialysis in the study of colloids - Part VII. Colloidal Zinc ferrocyanide

      V C Vora P M Barve B N Desai

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      The changes in the cataphoretic speed, stability and conductivity of colloidal zinc ferrocyanide dialysed, diluted, allowed to age and exposed to sunlight for different periods have been studied.

      With the progress of dialysis the cataphoretic speed first increases and then decreases, while the stability and conductivity continuously decrease.

      In the case of sols dialysed for periods shorter than the maximum in the cataphoretic speed-dialysis curve, the cataphoretic speed first increases and then decreases on dilution, while for sols dialysed for longer periods the cataphoretic speed continuously decreases. The stability and conductivity, however, continuously decrease on dilution in all the cases.

      It is found that for short period dialysed sols, the cataphoretic speed first increases and then decreases on adding small increasing amounts of KCl, K2SO4, K4Fe (CN)6, MgCl2 and MgSO4; for long period dialysed sols the cataphoretic speed continuously decreases with all the electrolytes except K4Fe (CN)6 where it first increases and then decreases. The idea of critical potential is not supported.

      On allowing both the short period and long period dialysed sols to age or exposing them to sunlight, the cataphoretic speed, stability and conductivity continuously decrease.

      The results are interpreted by means of assumptions similar to those employed in the case of the other colloidal solutions investigated in this laboratory.

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