  This paper presents, for ternary lysozyme-Na$_2$SO$_4$-water system, the
thermodynamic data extracted from the measured values of four ternary diffusion
coefficients and the Onsager reciprocal relations. The calculation for
derivatives of solute chemical potentials with respect to solute molar
concentrations was made using the method presented in \cite{1}. This method is
applicable to systems in which the molar concentration of one solute is very
small compared to that of the other, like in our case. The approach is
illustrated for the lysozyme chloride-Na$_2$SO$_4$-water system at 25$^o$ C, pH
4.5 and at 0.6 mM (8.6 mg/mL) lysozyme chloride and 0.1, 0.25, 0.5, 0.65, and
0.8 M Na$_2$SO$_4$ concentrations. The calculated solute chemical potential
derivatives were used to compute the protein cation charge approximately. We
also compute the diffusion Onsager coefficients $(L_{ij})_o$ for each
composition at pH 4.5.
