A couple new ways of surface tension determination

Axisymmetric liquid-fluid interface (ALFI) and axisymmetric drop shape analysis (ADSA) are the methods used in surface phenomena investigations. A photographed contour of a drop or a bubble is detected and fitted to numerically integrated Young-Laplace equation. However, ALFI fails in the stationery points, while ADSA gives the wrong surface tension value at the apex. An analytical expression for an interface shape overcome the weaknesses of the numerical models. It shows that pressure inside a drop is higher than outside, while a bubble encloses gas with negative gauge pressure. Since, the close-formed solutions origin from a force balance which preserves constant volume as well as temperature, entropy, and masses of ingredients are invariable the new formulas can be considered in the surface tension measurements. Hence, surface tension can be determined in the new ways. Each new method needs the measurements of two dimensions only and a solution of quite simple set of the equations. Moreover, the spare equations verify the solution. Then achieved surface tension is an input to obtain bubble shapes which are compared with experiment successfully. (C) 2017 Elsevier Ltd. All rights reserved.