The Origin of Viscosity in Suspensions

Einstein performed a mathematical analysis in 1906 on the origin of viscosity in suspensions, which may be described today as the classical 

In connection with the table, the origin of the different formulas will be discussed briefly and the most important conditions governing their validity indicated. 

The molecules of the dissolved substance are large in comparison with the free path of the molecules of the solvent, but small in comparison with the dimensions of the apparatus. The solvent is assumed to be incompressible. 

The suspended particles are rigid spheres to which the solvent liquid adheres completely. 

The concentration of the solution is so low that any mutual disturbance of the particles may be ignored. 

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