Surface tension measuring instrument，Including platinum plate method and platinum ring method. Surface tension is a fundamental property of liquids, especially aqueous solutions of surfactants.PZ-EFully automatic surface tension testerIt is a simple and practical instrument for testing surface tension using physical methods instead of chemical methods, which can quickly and accurately measure the surface tension values of various liquids. In the water and electricity sector, it is used to test the surface tension value for electrical use to strengthen the supervision of insulation oil quality. In the petroleum, chemical, scientific research, and education sectors, it can be used to test the surface tension value of various liquids, analyze various liquids, and use them in teaching, with a wide range of application fields.

1.1What is surface tension

Surface tension measuring instrumentIt is the tension generated on the surface of a liquid due to the uneven molecular gravity acting on any boundary line along the surface. The total force exerted by the surrounding molecules on a molecule inside a liquid is0But on the surface, a molecule is different. Due to the fact that the attraction of gas-phase molecules in the upper space is smaller than that of liquid phase molecules inside, the resultant force acting on the molecule is not equal to zero. The direction of the resultant force is perpendicular to the interior of the liquid, resulting in a tendency for the liquid surface to automatically shrink. This contraction force is called surface tension.

The molecules inside the liquid are almost closely adjacent to each other, and the molecules often remain close to each otherbalancedistanceThey attract each other from a distance and repel each other from a distance, which determines the liquidmoleculeUnlike gas molecules, which can diffuse infinitely and can only vibrate and rotate near the equilibrium position. The molecules near the liquid surface are only significantly affected by the molecules inside the liquid, resulting in uneven force distribution. This makes it easy for molecules with higher velocities to rush out of the liquid surface and become vapor. As a result, the molecular distribution in the liquid surface layer (the thin layer of liquid in contact with gas) is sparser than that in the internal layer. Compared to the distribution of molecules inside the liquid, they are in a special situation. The repulsion between molecules in the surface layer decreases as their distance from each other increases, and in this particular layer, the attraction between molecules dominates. The mutual traction force between any two parts in this surface layer,This promotes a tendency for the surface layer of the liquid to shrink. Due to the effect of surface tension, the liquid surface always tends to shrink as much as possible, so small droplets in the air often take on a spherical shape.

1.2Platinum Tour de France

The platinum ring method is obtained by forming a circular film between the testing part and the liquid sample.

The measurement method of platinum ring method is: (1) gently immerse the platinum ring into the liquid; (2) The platform descends, forming a water bubble film underneath the platinum ring and eventually separating from it; (3) The sensor measures the balance value, converts it into surface tension value, and displays it.

1.3Platinum plate method

When the platinum plate is immersed in the liquid to be tested, the surrounding area of the platinum plate will be subjected to surface tension, and the surface tension of the liquid will pull the platinum plate down as much as possible. When the surface tension and other related forces of the liquid reach equilibrium with the equilibrium force, the platinum plate will stop immersing into the interior of the liquid. At this point, the balance sensor of the instrument will measure the immersion depth and convert it into the surface tension value of the liquid.

The testing steps of the platinum plate method are: (1) platform rise; (2) When the bottom of the platinum plate is in full contact with the liquid surface, the sensor measures the equilibrium value, converts it into a surface tension value, and displays it.

1.4Comparison between Platinum Plate Method and Platinum Ring Method

1.The platinum plate method can measure the change of surface (or interface) tension of a liquid over time: When measuring with the platinum plate method, it is in constant contact with the liquid to be measured. As long as the surface tension of the liquid changes, the test value will also change. If data processing software is used, the surface tension curve over time can also be observed.

2.It is convenient to measure the surface tension of medium to high viscosity liquids: during the platinum ring test, the platinum ring needs to be lifted upwards, and in this process, in addition to the effect of surface tension, there is also the effect of viscosity.

3.High testing accuracy: Platinum plates are not easily deformed, while platinum rings are prone to deformation. The irregular circle and unevenness of the ring can affect the accuracy of surface tension testing.