A M Patel
Articles written in Proceedings – Section A
Volume 4 Issue 5 November 1936 pp 503-513
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.
Volume 10 Issue 5 November 1939 pp 344-358
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.