Mobile Monomers and Dimers in Precipitation Kinetics: a Microscopic Approach.

A microscopic theory of precipitation kinetics in solution developed previously by Ruckenstein and co-workers [ Dadyburjor , D. B. ; Ruckenstein , E. J. Cryst. Growth 1977 , 40 , 279 - 290 ; Bhakta , A. ; Ruckenstein , E. J. Chem. Phys. 1995 , 103 , 7120 - 7135 ] is generalized. The processes (not considered in the original approach) of monomer-monomer agglomeration, leading to the creation of dimers, as well as absorption (emission) of dimers by solute particles due to dimer mobility are included in the theory. The theory is applied to a model system in which particles grow up to a certain largest size and then precipitate from solution. The most important change in the system kinetics due to those two processes (monomer agglomeration to form dimers and dimer absorption and emission) is tremendous slowing of the asymptotic time behavior of the concentration of particles of largest size. This can be used to obtain experimental evidence for agglomeration of monomers and dimer mobility in the kinetics of real systems. The effect of trimer absorption (emission) is estimated, and it is shown that it is negligible in many situations.