SU631805A1 - Liquid surface tension determining method - Google Patents

Description

The invention is subject to methods for determining the physicochemical consanganging of a substance.

Methods are known for measuring the surface tension of liquid substances by the magnitude of capillary lift, the maximum pressure in a gas bubble or a liquid drop, by the method of a lying drop S.

The aim of the invention is to improve the reliability of measuring the surface tension of liquids having a high elasticity of saturated steam.

To do this, on the surface of the liquid under study, artificially create a relief by immersing a capillary or a narrow slit in two volumes of liquid one above the other at the height of the capillary lift, record the change in the mass of the liquid in the process of stationary di-fusion from one volume to another and determine Formula Surface Tension:

f is the packing factor (i l, 2-l, 24) j3jt is the density of a liquid N is the Avogadro number; W is molecular weight; T - universal gas constant, K - Bolan's constant; T is the temperature of the liquid; dM is the change in mass of the liquid during the time At in the process of stationary diffusion; capillary radius of the upper end.

The relief on the surface of the liquid during the experiment is kept constant.

Claims (2)

The method is illustrated by the design of the experimental setup shown in the drawing. 3. 63 Thin-walled glass ampoule 1 with capillary 2 is filled with the test liquid so that its level is slightly below the upper cut of the capillary. Then the ampoule is suspended to the shoulder of the sensitive balance 3 by means of a quartz filament 4. The lower end of the capillary is immersed in the container 5 with the same liquid. The vessel is placed on pad 6, which can freely move up or down with the micrometer screw 7. With this screw, the meniscus level in the capillary is set at the liquid level in the ampoule 1. The vessel 5 is placed in the air thermostat together with the ampoule and the capillary. With the help of a capillary or a narrow gap on the smooth surface of the liquid, they create or remove the profile or the scratches, and the process of healing them reduces to transferring the liquid from the upper vessel to the lower according to the evaporation – condensation scheme (evaporation with the surface of the liquid in the ampoule (sensation in the capillary or the gap, followed by transfer of the mass through the capillary into the lower vessel). The phenomenon can be described as follows. The pressure over the curved surface of the fluid at the interface with its own vapor is determined by the Thomson formula p-p «.E1, KTf, where SG is the surface tension coefficient; Too Steam pressure over a flat surface; - molecular weight; - fluid density, - Avogadro number, h radius of curvature of the meniscus, which is expressed in terms of the capillary radius h and the edge wetting angle -0 by the formula -j V-o. k is the Boltzmann constant; T is the temperature. Due to the pressure difference between the vapor of the liquid and the flat surface of the meniscus in the capillary, stationary diffusion takes place. In result, the amount of fluid in ampoule 1 varies over time. On the basis of the Fick law, the change in the quantity of a substance dM during the time of the dt process of stationary diffusion is: T-I ii Sg-hadh, C2) where E is the diffusion coefficient; h is the number of particles in 1. cm, S is the area; hi is the particle mass. Combining the diffusion equation of Ik with the Thomson equation, we get 2 (W) × RT.p de T is the temperature of the liquid, 1 is the gas constant. Using the well-known relation for the kinetic theory of gases for the coefficient of surface tension of the fluid being studied, we will have; In LAD A At d - l-f. (MN jkb 3 h BM / AfCM / VRT / B LL / KTg p., And 1.2f - packing factor 1.24). Apart from the known characteristics of the test ;; liquid being used, the level of aversion (4) includes two quantities: DM — reduction of iviaccbf liquid in ampoule 1 in time & i. and Vo is the radius of the upper end of the capillary. These values are determined experimentally. The proposed method can determine the surface tension not only of liquids wetting the capillary but also of liquids that do not wet the capillary; in the latter case, the experiment is conducted differently. Claim 1. Method for determining the surface tension of liquids, characterized by 470, in order to increase the reliability of determining the surface tension of liquids having high elasticity of saturated steam on the surface of the test liquid artificially create a relief by immersing a capillary or a narrow gap in two volumes of liquid placed one above the other at the height of the capillary lift, record the change in the mass of the liquid in the process of stationary diffusion from one volume to another and determine the surface tension ix formula: gn- Vi-8 / -RtN / JV. 3 H bl / fg / B 2Mj f - packing factor (f 1.21, 24); N is the Avogadro number; M is the molecular weight; R - universal gas one hundred nia; - constant Boltzmann; T is the temperature of the liquid; dM is the change in fluid mass over time during stationary diffusion, and is the radius of the upper end of the capillary. fluid density 2. The method according to p. 1, of t-l and h ayusch and the fact that the relief on the surface of the liquid in the process of the experiment is maintained unchanged. Sources of information taken into account in the examination: 1. Adam H, K., Physics and Surface Chemistry, ed. A. S. Akhmatova, OGIZ Ml. 1947, p. 466-487. //////////////////