Articles written in Proceedings – Section A
Volume 23 Issue 1 January 1946 pp 1-7
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.
Volume 23 Issue 2 February 1946 pp 47-59
Volume 24 Issue 3 September 1946 pp 261-276
Volume 25 Issue 2 February 1947 pp 162-173
The effect of variation of the temperature of precipitation of gels of hydrous oxides of silica, titania and alumina on the hysteresis effect in the sorption of water vapour has been studied at 30°C. Gels have been obtained by precipitating the hydrous oxides at 25°C. and 100°C. with previous boiling of the silicate solution.
In all the systems studied, permanent hysteresis loops have been obtained. With increase in the temperature of precipitation, there has been a diminution in the sorptive capacity of gels for water at different partial pressures and in most of the systems the hysteresis loop suffers a diminution in size with a change in the shape and position of the loop. But in none of these systems, is any complete elimination of the loop noticeable. Gels precipitated at 100°C. are less porous than the gels precipitated at 25°C. and appear to have fewer cavities that are responsible for the phenomenon of hysteresis.
Volume 25 Issue 2 February 1947 pp 174-180
The effect of the activation temperature of silica gel on the hysteresis effect has been studied. Sorption and desorption of water vapour at 30°C. have been conducted on gels activated at 35° C., 70° C., 140° C., 300° C., 500° C. and 1000° C.
All the gels gave permanent and reproducible hysteresis loops. A marked variation however, was noticed in the total sorptive capacity and the area of the loop.
The results indicate that from 35° C. to 140° C., there is a decrease in the capillary space in the gel but from 140° C. to 500° C., the capillary space remains practically unaltered. Whereas, above 500° C., the gel suffers structural change, the capillaries collapse and there is a marked decrease in the total capillary volume.
Volume 25 Issue 2 February 1947 pp 181-185
By employing the quartz fibre spring technique, the hysteresis in sorption has been studied, of water vapour at 30° C. on precipitated silicic acid gel. A comparative study has been made with regard to the shape and size of the hysteresis loops of precipitated silica gel with that of the adsorbent obtained from silicic jelly.
The mode of preparation of the gel was found to greatly influence the shape and size of the hysteresis loop.