Journal of Colloid and Interface Science, May 1981 [antikvár]

A New Method and Apparatus for Measuring Foam Stability GARY NISHIOKA' NASA, George C. Marshall Space Flight Center, Huntsville, Alabama 35812 and SYDNEY ROSS Chemistry Department, Rensselaer Polytechnic Institute, Troy, New York 12181 Received March 5, 1980; accepted September 24, 1980 The decay of foam with time, whether caused solely by gas diffusion through foam lamellae without rupture, or by a combination of that effect and occasional concomitant rupture, is given, most fundamentally, by the rate of decrease of the total area of extended liquid surface. This property can be measured directly, by photographing sections of the foam at measured intervals of time, but the technique and subsequent reduction of the observations to numerical values require so much effort that the direct method is seldom used. The equation of state of foam (Ross, S., Ind. Eng. Chem. 61, (10), 48 (1969)), however, relates the total area of liquid surface within a foam to the pressure of its contained gas, and so makes it possible to quantify foam decay in fundamental terms, by determining the rate of the build-up of gas pressure at constant volume and temperature in the head space above the foam. An apparatus is described that uses this principle. Pressure differences of the order of a few torricelli are measured by means of a differential pressure transducer, connected to a strip-chart recorder. The total area of extended liquid surface determined with this apparatus is in excellent agreement with results obtained simultaneously by direct photography of the foam during its decay, thus confirming the validity of the Ross derivation. The method of differential pressures was also used to confirm the effect, already well known, that the stability of foam made from an aqueous solution of sodium lauryl sulfate is enhanced by the presence of small amounts of lauryl alcohol in the solution. INTRODUCTION ods of measurement (5). However, none of The requirements to stabilize or, alterna- ^^ese methods is simultaneously versatile, tively, to destroy foam are problems that reproducible, expenmentally conveni- occur in a number of industrial processes, fundamental. We descnbe m this such as pulp and paper manufacture, froth "»^th^d and an instrument that satisfy flotation, distillation towers, coating proc- ^^^ desiderata, esses, fire fighting, and food processing. The method is based on the equation of Many different methods exist for the meas- f®«- f®^'".' ^^ derived by Ross (6). A urementoffoam stability, such as the Ross- considered to consist of cells, Miles method (1), Bikerman method (2), op- ^^ejher sphencal or polyhedral m shape, deal transmission methods (3), photographic containing gas at an excess pressure techniques (4), and various qualitative meth- corresponding to the radius of curvature of Its equivalent sphere (see Ref. (6) for the > U.S.R.A. Visiting Scientist (1978-1979). Present ^he equivalent sphere). The total address: Technical Center, Owens-Coming Fiberglas area of the foam is related to pressure, Corporation, P.O. Box 415, Granville, Ohio 43023. volume, temperature, and quantity of gas by 1 0021-9797/81/050001-07$02.00/0 Copyright © 1981 by Academic Press. Inc. Journal of Colloid and Interface Science, Vol. 81. No. 1. May 1981 All rights of reproduction in any form reserved.