The Molecular Properties of Ghatti Gum: A Naturally Occurring Polyelectrolyte

Sorption of water vapour and surface activity of ghatti gum

The sorption of water vapour by three fractions of sodium ghattate has been studied at 25° and 40°. The results were fitted by Brunauer, Emmett & Teller plots at low relative vapour pressures. Calculations of the differential heats and entropies of sorption gave initially exothermic ΔH̄ values and negative ΔS̄ values. As the sorption proceeded the signs of the thermodynamic properties became positive The mechanism of sorption onto different parts of the macromolecules was discussed.

The surface tension of one sodium ghattate fraction was measured in water, 0.05 and 0.5 N sodium chloride solution, as a function of concentration, using the sessile drop method. The presence of salt enhanced the surface activity. A structure for the adsorbed film is suggested.

Peter Howard Elworthy (1933-1995): a biographical note

Peter Elworthy had a considerable influence on pharmaceutical science, education and practice, in the UK. He died in December 1995 at the early age of 62, but he had retired from full time academic work from his post as Professor of Pharmacy and Head of the Department of Pharmacy in the University of Manchester twelve years earlier. Concerned about his health but also not a little disillusioned by the multiple pressures placed even then on senior academics, he foresaw the era of cuts and the central oversight and restrictions. His heart was elsewhere. In his 1976 Harrison Memorial Lecture (reproduced in this issue) he said: "Looking back, I have the feeling of having been very lucky. 'Much have I travell'd in the realms of gold, and many goodly states and kingdoms seen.' My main interest has been in the phenomenon of micellization. The subject has been of absorbing interest, and continually shows new bright facets which lead to new scientific advances. Travelling in the realms of gold has nothing to do with gold, but to me it means travelling in sunlight, which illuminates things brightly, and makes visible new facts, which have been invisible before. Occasionally dark clouds form; they are the disappointments and frustrations, but we need them in order to be able to recognize the sunlight by contrast."