METHOD OF MEASURING CONCENTRATION OF SURFACE-ACTIVE SUBSTANCE Russian patent published in 2005 - IPC

FIELD: measuring engineering.

SUBSTANCE: method comprises generating thermocapillary convection by laser beam in a layer of fluid on the substrate which absorb laser radiation. After the light beam is turned on, the substrate begins to liberate heat, and heat front propagates from the substrate to the free surface of fluid through the layer. Once the front attains the free surface, the heat front induces the capillary flow which results in the dynamical deformation of the free surface of the layer providing a hollow. The higher concentration of the surface-active substance, the higher temperature is required for generating thermocapillary flow and, the longer time lag required for free surface to be deformed. The deformation is indicated on the screen as the deviation of the diameter of the beam spot from its value corresponding to the reflection from the flat free surface or as change in the distribution of the spot intensity. The concentration of the surface-active substance can be judged by the time interval between the moment of the turning on of the laser beam and the moment of the onset of variations of the diameter or distribution of the spot intensity on the screen. An experimental dependence of the time interval on the individual surface-active substance concentration should be obtained. The dependence is used then as a calibration one for the measurement of concentration of this surface-active substance.

EFFECT: simplified method and reduced time consumption for measurements.

3 dwg