SE0300329D0 - Procedures and instruments for measuring surface tension - Google Patents

Abstract

In measuring the surface tension between a liquid and fluid such as a gas, a capillary (3, 3') is used in which the liquid is slowly flowing and at the end of which drop (11) are formed and fall off inside a closed space (7) containing the fluid. Using a measurement device (5, 5'), that for example can be of optical nature, the times are measured when a drop reaches a predetermined size and when a drop falls off. The time period from the time when a drop has reached a predetermined size until it falls off and the time period until the next drop reaches the predetermined size are used for calculating the surface tension of the liquid. The measurement can be made rather rapidly and with a high operational reliability and is relatively little influenced by variations in the feeding velocity for the fluid. The temperature difference between the drop and the surrounding fluid is small, this causing a small precipitation of salts dissolved in the liquid and reducing the risk of blocking the liquid capillary. A pump (31) connected to the outlet (9) of the closed space (7) produces a subatmospheric pressure in the fluid in the closed space and hence makes liquid flow up to the end of the capillary to there form the drops (11). Since the fluid in the closed space (7) is compressible, it will attenuate possible pulsations and interference derived from the pump (31), so that they do not affect the growth and falling-off of the drops (11). The attenuation of pulses allows the use of a simpler, more robust and more industrially resistant pump to achieve the required liquid flow through the capillary (3).