Dynamic surface tensiometry and method

Apparatus for measuring dynamic surface tension at a gas-liquid interface by the maximum bubble-pressure method comprising

• a bubble orifice tube having non-wetted surfaces adapted to be immersed in the liquid at a predetermined depth;
• automatic gas delivery means including a supply of gas under pressure and in flow-series therewith a first flow-restricting capillary, an accumulator zone for storing gas from the first capillary, a second capillary of lower flow resistance than the first, a relatively unrestricted delivery tube connecting the second capillary to the bubble tube, and atmospheric vents for the accumulator zone and the delivery tube automatically closable to start bubble formation, such means delivering gas to the orifice tube at a rate rising steadily over an interval of time to increase the frequency of bubble formation at least several fold;
• and
• a bubble pressure measuring system including a pressure-measuring transducer in free communication with the bubble tube and providing electrical output instantaneously indicative of the pressure in each bubble, a peak-detecting circuit responsive to the transducer output providing a signal indicative of the maximum bubble pressure, a converter circuit responsive to the transducer output providing a signal indicative of the frequency of bubble formation, and a recorder responsive to the said two signals adapted to display a spectrum of the maximum bubble pressures in units directly indicative of surface tension as a function of the frequency of bubble formation.