A single-parameter method for the determination of surface tension and contact angle

The classical problem of determination of liquid surface tension from the shape of a sessile drop is reinterpreted. A non-dimensionalisation, first suggested by Smolders, is chosen in which the shape of the drop is characterized solely by the value of the Bond number in which the observed maximum radius of the drop appears as a characteristic length. The Bond number is defined as Bo = gr2max/¿, where is the density, ¿ is the surface tension of the liquid, g is the acceleration due to gravity and rmax is the maximum half width of the drop. A graphical presentation of the results allows an immediate comparison with experimental drops, eliminating the use of iterative procedures. Graphs from which the contact angle can be read are also presented. A computer code is given for those cases where a refined approach is necessary. The power of the method is to be found in its simplicity and its diagnostic capabilities. Comparisons with experimental results are given