Equations in the ion-interaction (Pitzer) system are derived for the volume change on mixing any combination of the sea salts NaCl, Na2SO4, MgSO4, MgCl2 at constant ionic strenth. For these mixings of different charge types, the equations include complex differences of pure electrolyte terms. Recently measured data for each of the pure electrolytes provide these pure electrolyte terms. Other recent measurements on the volume change on mixing are compared with values calculated from the equations. At 25°C there is no need to introduce the mixing terms based on differences in the interactions of ions of the same sign. At other temperatures, the agreement without the mixing terms is good, but significant improvement is obtained by inclusion of the binary mixing terms θCl,SO4v and θNa,Mgv. The equations and parameters can then predict the volumetric properties of any mixed solution of these salts over the range 0-100°C and to at least 3 mol-kg-1 ionic strength.
- Sea salts
- volumes of mixing
ASJC Scopus subject areas
- Molecular Biology
- Physical and Theoretical Chemistry