Evaluation of the effects of some additives and pH on surface tension of aqueous solutions using a drop-weight method

Abstract

In the present study a simple drop-weight method was used as a technique to measure the surface tension of various aqueous solutions. A newly modified version of the Harkins–Brown correction factor was proposed in order to improve the accuracy of the drop-weight method. The applicability of this newly proposed correction factor was tested with various aqueous solutions, i.e., sucrose, NaCl as well as acetic acid solutions, and it was found that the deviation between the calculated and standard values of surface tension of these solutions was less than 2.5%. The technique was then used to study the effects of selected additives and pH on the surface tension of aqueous solutions. The results showed that addition of hydrocolloids decreased the surface tension of the solutions to various extents while addition of tapioca starch did not affect the surface tension of the suspension. It was also found that the type of acid used to adjust the pH affected the surface tension of aqueous solutions differently although the pH of the solutions was equal.