A fluid inside a glass U-tube will vibrate at a certain frequency depending on the mass and temperature. The measured frequency is compared to known calibration points for accurate results. 

Refractive index measurements are primarily used to quantitatively compare different samples. It is affected by parameters that are not so easily measured in other ways, such as concentration and purity.

Two common methods to measure the surface tension and interfacial tension is through the Wilhelmy Plate method or the du Noüy Ring method. A high-resolution balance measures the force required to remove the probe from the liquid. 

Viscosity measurements are primarily used to quantitatively compare different samples. It is affected by parameters that are not easily measured in other ways, such as molecular weight, molecular weight distribution, and even consistency between batches.