What is Surface Tension?

Five Commonly Used Methods for Measuring the Surface Tension of Liquids

Introduction:

The force acting on the surface of the liquid to reduce the surface area of the liquid is called the surface tension of the liquid. The reason for it is that there is a thin layer on the surface where the liquid is in contact with the gas, called the surface layer. The molecules in the surface layer are sparser than the inside of the liquid, and the distance between the molecules is larger than the inside of the liquid. The interaction between the molecules is manifested as gravitational force. Tension measurement methods mainly include platinum plate method, platinum ring method, rotating drop method, hanging drop method, and bubble pressure method.

Five Kinds of Testing Method for Measuring the Surface Tension:

1. Platinum plate method: When the sensor is immersed in the liquid to be measured, the surface tension around the platinum plate will be affected, and the surface tension of the liquid will pull down the platinum plate as much as possible. When the liquid surface tension and other related forces and balance forces reach equilibrium, the sensing platinum plate will stop immersing into the liquid. At this time, the balance sensor of the instrument measures the immersion depth and converts it into the surface tension value of the liquid.

2. Platinum ring method: Because it is widely used in du Nouy surface tensiometer, this method is also called du Nouy method, and it is widely used because of its simple operation. The term platinum ring method is derived from the formation of a ring between the test part and the liquid sample.

3. Rotating drop method: The basic principle of the rotating drop method is to obtain the interfacial tension from the shape and size of the drop according to the Bashforth-Adams equation. The drop is placed in a certain centrifugal force field by rotation, and the balance shape of the drop can be changed by adjusting the rotation speed. To facilitate the determination. Mainly measure ultra-low interfacial tension.

4. Pending drop method: calculate the surface tension by processing the image of the largest drop.

5. Bubble pressure method: The capillary is connected to the gas interface and the sensitive pressure sensor. The gas passes through the capillary and forms a bubble at the end of the capillary. The pressure of the bubble is measured and converted into surface tension.

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