METHOD FOR DETERMINING COEFFICIENT OF SURFACE TENSION OF LIQUIDS BY MEANS OF SPREADING METHOD Russian patent published in 2015 - IPC G01N13/02 

FIELD: measurement equipment.

SUBSTANCE: invention relates to investigation of surface phenomena and is intended for reliable determination of a coefficient of surface tension of liquids σ₂₁. This coefficient means surface tension of liquid (2) at the boundary with its vapour (1) or another gas. A method for determining a coefficient of surface tension of the liquid by means of a spreading method involves determination of thickness of an equilibrium layer of the spread liquid. Besides, the method involves determination of hydrostatic pressure forces and determination of a surface tension force at the boundary between the liquid and a solid substrate - a force of inter-phase tension. Additionally, a coefficient of inter-phase tension is determined between a certain substrate and the test liquid. After that, the coefficient of surface tension of the liquid is determined by using equations by the following formulas: for a full wetting case 0.785ρgh²+σ₃₂cosθ-0.5σ₂₁-σ₂₁=0, for a full non-wetting case 1.57ρgh²+σ₃₂cosθ-σ₂₁-σ₂₁=0, where ρ - density of the test liquid; g - acceleration of gravity; h - thickness of the equilibrium layer of the spread liquid; σ₃₂ - coefficient of inter-phase tension in a "substrate material - test liquid" system; σ₂₁ - coefficient of surface tension of the test liquid.

EFFECT: obtaining reliable values of a coefficient of surface tension of the main liquids.