Pulsations on mercury surface caused by polarisation

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Efficiency of wetting agents

The relative efficiencies of some of the common wetting agents have been determined by measuring the surface tension of five-minute-old surfaces of the solutions using the ring method in a modified form. Aqueous solutions giving a surface tension of 37 dynes per cm. may be considered to have good wetting properties. It is found that wetting power is not necessarily associated with detergent and emulsifying properties. Salts greatly increase wetting power. Bivalent cations are more effective than univalent cations in increasing wetting power. A moderate degree of hardness in water employed in preparing solutions of wetting agents may be of advantage in the textile industry. The maximum bubble pressure method is shown to be unsuitable for the measurement of surface tension of solutions which show a variation with time. A rough idea of the order of wetting efficiencies of wetting agents can however be obtained by measuring the surface tension of a five-second-old surface by this method

Effect of electric field on Tyndall scattering

The study of the action of an electric field on the scattering intensity of sols has thus led to interesting results. The study is useful in determining the shape of the particles. The present technique would be supplementary to the studies of double refraction, in that the latter cannot be conveniently investigated in a highly scattering system. With slightly conducting sols, large fields can be used so as to produce saturation effects. Under such conditions, the use of rotating fields would bring about a unique orientation of the discs. A superposition of two A.C. fields of different cycles at right angles to each other would have the same effect as the circular field. The use of elliptical fields would reveal any want of equality of the two axes in the plane of discs of flat particles. The technique itself is simpler than the flow technique. Since there is often a large difference in the dielectric constant between the particles and the medium, the orientation is marked even with small fields, and the electric field is thus more powerful than the magnetic field in bringing about orientation

Spreading of casein and derivatives

1. Casein has been spread from its aqueous solutions by different methods and it has been found that the modified band method is the most suitable for the study of protein films. 2. Effect of salts on the spreading of casein has been studied. The results obtained can be explained on the basis that two different factors, solubility and the electric charge of the protein molecule influence spreading. 3. Treatment of the protein with formaldehyde causes a decrease in spreading. Change in pH affects spreading of formolised casein to a smaller degree. 4. Sodium metaphosphate diminishes markedly the spreading of casein. Trichloracetic acid, however, has no effect. 5. Deaminisation of casein alters the spreading properties and gives unstable films on acidulated water. No films can be got on distilled water. 6. The spreading properties of an isodisperse fraction of casein have been studied. The limiting area of this fraction has been found to be of the same order as that of the original material

Selective adsorption on silica gel from pyridine-alcohol mixtures

Refractive indices of pyridine-ethyl alcohol mixtures have been measured at 23°·37 C. The selective adsorption on silica gel from pyridine-ethyl alcohol mixtures has been measured over the entire range of concentration. The selectivity concentration curve is found to be of the S-type. Evidence is adduced to show that an adsorption compound C5H5N, 2 EtOH is formed at the interface. In conclusion the authors wish to thank Professor B. Sanjiva Rao for his interest in the work. © 1937 Indian Academy of Sciences

Ageing of surfaces of solutions. I: The study of variation of surface tension of solutions with time by the ring method

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Redoxokinetic titration: a new analytical technique

It is shown that the end-point in the titration of ferrous salts with ceric salts and that in the titration of iodine solution with sodium thiosulphate can be determined precisely by taking advantage of the sudden change of redoxokinetic potential at the end point. This technique, which has been named as redoxokinetic titration, appears to have good potentialities of application in analysis