Method and apparatus to measure surface tension by inverted vertical pull

Abstract

A method and apparatus is presented for determining surface tension of a liquid or interfacial tension between two dissimilar liquids by using a rigidly suspended probe with small sample sizes and by measuring probe force using a top-loading balance used for supporting the container of liquids under test. When a small sample size in a small container is used, capillary action between a probe and the container walls enhances the measured force, and an adjustment factor for the capillary action must be applied. A probe rigidly suspended to overcome capillary action between the probe and walls permits such measurements. For any sized sample, in accordance with Isaac Newton's third law of equal and opposite forces acting between objects, the force required for lifting a probe vertically from a liquid is equivalent to the reduction in weight of the liquid and container. Force magnitude is thus determined using a top-loading balance for observing weight change, either in the liquid while a suitably configured probe is withdrawn from the liquid or in a probe suspended by a direction converter resting on a top-loading balance while the container and liquid are lowered.