Method for determining the dynamic surface tension of liquids
A measuring capillary is immersed in the solution to be tested and air (or another gas) is passed through it at a defined flow rate. The surface tension of the liquid is calculated via the gas pressure building up at the end of the capillary. As the frequency of bubble formation decreases, the duration of existence of the bubbles increases, corresponding to a higher surface age.
Investigation of dynamic processes of surface-active compounds.
Method for measuring the surface and interfacial tension of liquids.
In the Wilhelmy plate method, the lower edge of a vertically suspended, rectangular platinum plate is brought into contact with the liquid to be measured and thus wetted. The surface tension of the liquid can be calculated from the force with which the plate is pulled out of the liquid.
In the De Noüy ring method, the ring, fully wetted with measuring liquid, is drawn through the liquid-liquid or liquid-gas interface. A liquid lamella constitutes on the ring, which enlarges the interface. The surface or interfacial energy can be calculated from the repulsive force.