Accurate Surface Tension Research Articles

Wall effects in measurement of surface tension using a vertical cylinder. Part 2.—Experimental

Experimental measurements on water and organic liquids provide quantitative confirmation of the theoretical model described in part 1 and show how the vertical cylinder can be used to provide accurate surface tension data, when only small volumes of liquid are available.

Some remarks on the accurate and absolute measurement of surface tension by a vertical plate method

A method for measuring an accurate and absolute surface tension using the so-called vertical plate technique was devised. The apparatus consists of a torsion balance and a glass plate; care was taken to avoid creep of the torsion wire and variation of a torsion constant in order to maintain a sufficient sensitivity. The equation for calculating an absolute surface tension was derived. The method is suited especially for the measurement of the surface tension and its changes over a long period, as shown by the aqueous surfactant solutions.

Accurate surface tension and charge determinations from polarographic drop-times

The precise determination of drop-times for micropolarographic mercury electrodes in aqueous inorganic electrolytes with and without the addition of organic surface-active compounds is described. A dependable mathematical method for conversion of drop-times to accurate surface tension data and the use of IBM computer techniques for the calculation of double layer parameters are discussed. Experimental results for hydrochloric acid, potassium chloride, and furfurylamine systems are reported.

The surface tension of sodium dodecylsulfate solutions and the phase separation model of micelle formation

A method for obtaining accurate and precise surface tension measurements of surfactant solutions above the c.m.c. is described. It depends on purification by foaming below the c.m.c., followed by fractionation into a more concentrated and more dilute solution. Data are obtained as the concentration is varied by recombining the two solutions until a return to the initial value shows the absence of contamination during the whole operation, which is performed in a compact apparatus. The effect of typical contaminants was also studied and their complete removal ascertained. A modified equilibrium Wilhelmy method was used and its accuracy is discussed. The results show a significant decrease of the surface tension of solutions of sodium dodecyl sulfate above the c.m.c. proving that its activity increases in this range. This finding places a definite limit upon the validity of the approximation represented by the phase separation theory of micelle formation. On the other hand, another approximation, a simple mass action calculation, accounts remarkably well for the data. Measurements below the c.m.c. obtained by essentially the same method indicate a significant increase of adsorption throughout this region.