A simple expression for the chemical potential of a solute in solution is presented under the superposition approximation. In this expression, only the knowledge of the solute-solvent pair correlation function within the solute-solvent interaction range is required to evaluate the chemical potential. The renormalization of the solute-solvent interaction is shown to be related to the indirect part of the solute-solvent potential of mean force. An inconsistency involved in the superposition approximation is then pointed out, and its origin is identified. The shift in a chemical equilibrium in solution induced by insertion of a solute is also investigated under the superposition approximation. It is shown that a correlation function characterizing the effect of a single solvent molecule on the chemical equilibrium plays an important role in determining the shift in the chemical equilibrium. Numerical results are presented for the chemical potential of hard sphere fluid.