This book contains the five classic Einstein papers on Brownian motion. The last paper is a simplified explanation of Brownian motion for chemists.
Investigations on the Theory of the Brownian Movement
A. Einstein, Annalen der Physik, 17, 1905, p549
On the Theory of the Brownian Movement
A. Einstein, Annalen der Physik, (4),19,1906, pp378-381
A New Determination of Molecular Dimensions
A. Einstein, Annalen der Physik, (4), 19, 1906, pp289-306
Theoretical Observations on the Brownian Motion
A. Einstein, Zeitschrift für Elektrochemie, 13, 1907, pp41-42
Elementary Theory of the Brownian Motion
A. Einstein, Zeitschrift für Elektrochemie, 14, 1908, pp235-239