Diffusion approximations for some simple chemical reaction schemes

We shall establish functional limit laws for the concentration of the various species in simple chemical reactions. These results allow us to conclude that, under quite general conditions, the concentration has an approximate normal distribution. We provide estimates for the mean and the variance which are valid at all stages of the reaction, in particular, the non-equilibrium phase. We also provide a detailed comparison of our results with the earlier work of Dunstan and Reynolds ([7], [8]).