A model for calculating the heat capacity of complex aqueous solutions with an arbitrary number of solutes and at an arbitrary temperature was developed. Parameters for 79 solutes were established based on a critical review of the literature for solutions of one solute in water, with about 6600 points included. The average difference between the calculated and experimental heat capacity is -0.0003 kJ.kg(-1).K(-1) with a standard deviation of 0.010 kJ.kg(-1).K(-1). The model was validated by comparing published and calculated heat capacities for 13 systems of more than one solute in water, with a total of 485 data points. The average difference between experimental and calculated values is -0.003 kJ.kg(-1).K(-1) with a standard deviation of 0.029 kJ.kg(-1).K(-1). Data are presented on the following 109 solutes, including data on density (16 300 points) and viscosity (10 700 points): (NH(4))(2)SO(4), Al(2)(SO(4))(3), AlCl(3), Ba(NO(3))(2), BaCl(2), Ca(CH(3)CO(2))(2), Ca(NO(3))(2), CaCl(2), CaSO(4), Cd(NO(3))(2), CdCl(2), CdSO(4), CH(3)CH(2)OH, CO(2), CoCl(2), CoSO(4), Cr(2)(SO(4))(3), CrCl(3), Cu(NO(3))(2), CuCl(2), CuSO(4), Fe(2)(SO(4))(3), FeCl(2), FeCl(3), FeSO(4), H(2)O(2), H(2)SO(4), H(3)AsO(3), H(3)AsO(4), H(3)PO(4), HBr, HCH(3)CO(2), HCHO(2), HCl, HCN, HNO(3), K(2)CO(3), K(2)Cr(2)O(7), K(2)HPO(4), K(2)SO(4), K(3)PO(4), KBr, KCH(3)CO(2), KCHO(2), KCl, KF, KH(2)PO(4), KHCO(3), KHSO(3), KI, KNO(2), KNO(3), KOH, Li(2)SO(4), LiCH(3)CO(2), LiCl, LiNO(3), LiOH, Mg(CH(3)CO(2))(2), Mg(NO(3))(2), MgO(2), MgSO(4), Mn(NO(3))(2), MnCl(2), MnSO(4), Na(2)C(2)O(4), Na(2)CO(3), Na(2)CrO(4), Na(2)HPO(4), Na(2)MoO(4), Na(2)S, Na(2)S(2)O(3), Na(2)SO(3), Na(2)SO(4), Na(2)WO(4), Na(3)PO(4), NaAl(OH)(4), NaBr, NaCH(3)CO(2), NaCHO(2), NaCl, NaClO(3), NaF, NaH(2)PO(4), NaHCO(3), NaHS, NaHSO(3), NaHSO(4), NaI, NaMnO(4), NaNO(2), NaNO(3), NaOH, NH(3), NH(4)Cl, NH(4)HCO(3), NH(4)NO(3), Ni(NO(3))(2), NiCl(2), NiSO(4), Pb(NO(3))(2), SO(2), Sr(NO(3))(2), SrCl(2), Sucrose, TiOSO(4), Zn(NO(3))(2), ZnCl(2), ZnSO(4).