In 1893 William Sutherland, an Australian physicist, published a relationship between the dynamic viscosity, , and the absolute temperature, , of an ideal gas. This formula, often called Sutherland's law, is based on kinetic theory of ideal gases and an idealized intermolecular-force potential. Sutherland's law is still commonly used and most often gives fairly accurate results with an error less than a few percent over a wide range of temperatures. Sutherland's law can be expressed as:
- is a reference temperature.
- is the viscosity at the reference temperature
- S is the Sutherland temperature
Some authors instead express Sutherland's law in the following form:
Comparing the formulas above the constant can be written as:
- Sutherland, W. (1893), "The viscosity of gases and molecular force", Philosophical Magazine, S. 5, 36, pp. 507-531 (1893).