About 1905 Einstein published a work about diffusion of hard spheres and brownian motion. One effluence of that is the so called "Viscosity Equation" which was/is very important for dertermining moleculat weight of macromolecules by viscosity of solutions.
http://www.ias.ac.in/initiat/sci_ed/resources/chemistry/Viscosity.pdf
http://en.wikipedia.org/wiki/Intrinsic_viscosity
What I like to know: Was there any relation to the other
topics Einstein worked on? Is something known on Einsteins reason
work on Viscosity?
Georg