Fundamental properties, density (ρ) and viscosity (η), of citric acid (CA) and disodium hydrogen orthophosphate (DSP) at various strengths were obtained at different temperatures. The ρ and η values were used to determine apparent molal volumes and viscosity of systems. The ρ, VΦ and η values were regressed against molalitym for ρ0, η0 and VΦ0, the limiting constants at infinite dilution (m → 0) for ionic and molecular interactions. The ρ0 and VΦ0 of aq. acids are higher than those of aq. DSP and the viscosity of DSP is higher than that of aq. CA. Examination of ρ0 and VΦ0 functions indicates that mutual compositions of CA and DSP counterbalance concentration and temperature effects on pH in bioprocesses.
