IN the process of forecasts, analyses and numerical treatments of the ground water resource, we often meet with various chemical reaction models. One type of them is three kinds of chemical substance M_1, M_2 and M_3 which can react with each other to produce two new kinds of other chemical compounds: (M_2)_n (M_1)_m and (M_3)_r (M_1)_κ at the same time. Usually, these reactions are irreversible and they have the following forms: