• B N Desai

      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.

    • Conductivity and cataphoretic speed measurements of Benzopurpurin 4B, Congo Red and Sky Blue F.F.

      B N Acharya A M Patel B N Desai

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      Measurements of conductivity and cataphoretic speed of pure Benzopurpurin 4B, Congo Red and Sky Blue F.F. have been made and it is found that on increasing the concentration of the dye solutions although the equivalent conductivity continuously decreases the cataphoretic speed increases regularly. The cataphoretic speed of Benzopurpurin 4B first increases and then decreases with the progress of dialysis. On adding small increasing amounts of sodium chloride to Benzopurpurin 4B and Congo Red and barium chloride to Sky Blue F.F. the cataphoretic speed first increases and then decreases. The changes in conductivity and cataphoretic speed are explained on the basis of aggregation of the dye ions to form ionic micelles. It is shown that the process of dyeing of cotton fibre by substantive dyestuffs in the presence of salt can be easily understood on the basis of aggregation of dye ions.

    • 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.

    • The south-west monsoon

      B N Desai

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      A review has been made of the ideas about the south-west monsoon upto 1963 and the modifications necessary in the same in the light of the results of the International Indian Ocean Expedition (IIOE) during 1963–64. Important papers on the IIOE results published in India and elsewhere have been discussed in brief from the point of their usefulness in forecasting, indicating in what respects the interpretations are against weather, climatic and topographical features of the Indo-Pakistan subcontinent. Taking into account the presence of the Western Ghats, changes which occur within about 500 km. of the west coast of the Peninsula regarding clouds and weather and depth of the moist current brought to light by the IIOE results, become intelligible. There are no cyclonic circulations in the north-east Arabian Sea and Bombay area and in the South Bay of Bengal of the type of ‘subtropical cyclone’ in the eastern Pacific; existence of the same has been postulated due to inadequate appreciation of the Indian conditions by the workers concerned.

    • Causes of aridity and inversion over the desert areas of West Pakistan and neighbourhood during the south-west monsoon season

      B N Desai

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      Views of Flohn (1965, 1966) and of Ramage (1966) regarding the causes of aridity and inversion over the desert areas of West Pakistan and neighbourhood have been examined. It is shown on the basis of climatic features of the area that the inversion is due to air masses andnot due to subsidence; the aridity of the region is due to absence usually of a mechanism which can break up the inversion andnot due to the restricted depth of the moist current.

    • Air-mass dynamics or subsidence processes in the Arabian Sea monsoon

      B N Desai

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      Soundings over the Arabian Sea during the International Indian Ocean Expedition period and climatological data over the west coast of India have been discussed to determine the cause of the low-level inversion and the influence of the Western Ghats on the inversion and precipitation. There does not appear relation between maximum divergence and lowest height of base of inversion as presumed by Flohnet al. The pattern of precipitation frequency on the west coast as seen from Fig. 2 of Ramage does not show the same trend either as the number of rainy days or rainfall at the coastal observatories. The depth of the moist layer and the height of base of inversion increase as the Western Ghats are approached, such changes not occurring off west Kathiawar-Kutch-Sind where there are no orographic barriers on the coast.

      The air-mass considerations to explain the low-level inversion over the Arabian Sea, would appear substantially valid even now.

    • Meteorological conditions on days of radon measurements in air over the eastern Arabian Sea off Bombay

      B N Desai S K Subramanian T M Sambamoorthy

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      Meteorological conditions prevailing over and west of Bombay on the four days on which Bhatet al. (1974) made measurements of radon concentration at different altitudes from the surface to 3·7 km and distances of 0–50 and 350–400 km west of Bombay, do not appear to support their conclusions about airmasses.

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