G M Nabar
Articles written in Proceedings – Section A
Volume 29 Issue 4 April 1949 pp 277-287
The measurement of oxidation potential of dilute solutions of sodium hypochlorite has been carried out at 30° C. by a method used successfully by various investigators.
The values of the oxidation potential at 30° C. are higher than those at 20° C. The differences in the potentials become more and more marked with reduction in the pH of the hypochlorite solution.
A correction of pH × 0·06 volts to the measured potentials at 30° C. does not show any maximum value over the pH region examined. A sharp change in the direction of pH-corrected oxidation potential curve, however, occurs at about the same pH at which a maximum is obtained at 20°C.
There exists no similarity between the corrected oxidation potential-pH curve at 30° C. and a curve showing relation between oxygen uptake or fluidity and pH at 30° C. Nabar, Scholefield and Turner1 had shown a striking resemblance between these curves at 20° C.
Volume 31 Issue 4 April 1950 pp 234-239
Volume 31 Issue 6 June 1950 pp 371-380
Volume 32 Issue 4 October 1950 pp 212-231
When cellulose is oxidised with a mixture of nitrogen dioxide and oxygen the products obtained (I) dissolve in dilute alkali when the carboxyl content is about 9% as compared with a minimum of 13·5% required for alkali solubility in case of nitrogen dioxide oxycelluloses (II).
I usually possesses a higher percentage of combined nitrogen than II.
The yellow colour developed on treatment with hot dilute caustic soda disappears more or less completely if the oxycelluloses (except I) are treated with chlorous acid. In case of I, the intensity of the colour is diminished considerably.
There is a greater decrease in cuprammonium fluidity on treatment with chlorous acid with I and periodic acid oxycelluloses as compared with II and dichromate oxalic acid oxycelluloses.
On treatment with alkali there is a fall in copper number both in the case of I and periodic acid oxycellulose while an increase in copper number takes place in the case of II and dichromate-oxalic acid oxycellulose. Based on the above conclusions a tentative mechanism of oxidation has been suggested for the oxidation of cellulose with a mixture of nitrogen dioxide and oxygen.
Volume 32 Issue 4 October 1950 pp 232-239
Volume 32 Issue 5 November 1950 pp 319-329
The relation between pH of sodium hypochlorite solutions and the amount of oxygen consumed at 30°C. by cotton in presence of ferrous hydroxide and a number of vat dyes belonging to different chemical structural groups, is determined.
It is found that the reduced substances do not show uniform behaviour. The rate of oxygen uptake, the amount of oxygen transferred and the pH of maximum oxygen uptake by the cellulose substrate, are dependent on the individual reducing substance present on the fibre during the hypochlorite treatment.
At 30°C., there exists no similarity between the pH-corrected oxidation potentials curve and the curve showing relation between pH and oxygen uptake or fluidity.
The corrected oxidation potentials as obtained by applying a correction of 0.·06×pH volts to the measured value of the potentials is not a measure of the oxidising intensity of hypochlorite solutions.
Volume 34 Issue 2 August 1951 pp 101-120