Method for measuring changes in surface tension on agar.

The surface tension of agar surfaces was determined by measuring the contact angles formed by drops of various hydrophobic liquids on the surface and then calculating the composite surface free energy function by solving a series of simultaneous equations derived from these data. This method was used to measure the change in the surface tension of agar produced by the addition of various concentrations of albumin. The resulting curve was typical of the effect of increasing concentrations of surfactants on surface tension. The method was compared with other methods of determining surface tension of solids, and it was concluded that the technique used here provided the most reliable results.