Mean Activity Coefficients of Electrolytes as a Function
of Concentration
The mean activity coefficient γ of an electrolyte Xa
Yb
is defined
as
	
γ γ γ= + −
+
( ) /( )a b a bl
where γ+
and γ–
are activity coefficients of the individual ions
(which cannot be directly measured). This table gives the mean
activity coefficients of about 100 electrolytes in aqueous solution
as a function of concentration, expressed in molality terms. All
values refer to a temperature of 25 °C. Substances are arranged in
alphabetical order by formula.
References
	 1.	 Hamer, W. J., and Wu, Y. C., J. Phys. Chem. Ref. Data, 1, 1047, 1972.
	 2.	 Staples, B. R., J. Phys. Chem. Ref. Data, 6, 385, 1977; 10, 767, 1981; 10,
779, 1981.
	 3.	 Goldberg, R. N. et al., J. Phys. Chem. Ref. Data, 7, 263, 1978; 8, 923,
1979; 8, 1005, 1979; 10, 1, 1981; 10, 671, 1981.
Mean Activity Coefficient at 25 °C
m/mol kg–1
AgNO3
BaBr2
BaCl2
BaI2
CaBr2
CaCl2
CaI2
0.001 0.964 0.881 0.887 0.890 0.890 0.888 0.890
0.002 0.950 0.850 0.849 0.853 0.853 0.851 0.853
0.005 0.924 0.785 0.782 0.792 0.791 0.787 0.791
0.010 0.896 0.727 0.721 0.737 0.735 0.727 0.736
0.020 0.859 0.661 0.653 0.678 0.674 0.664 0.677
0.050 0.794 0.573 0.559 0.600 0.594 0.577 0.600
0.100 0.732 0.517 0.492 0.551 0.540 0.517 0.552
0.200 0.656 0.463 0.436 0.520 0.502 0.469 0.524
0.500 0.536 0.435 0.391 0.536 0.500 0.444 0.554
1.000 0.430 0.470 0.393 0.664 0.604 0.495 0.729
2.000 0.316 0.654 1.242 1.125 0.784
5.000 0.181 18.7 5.907
10.000 0.108 43.1
15.000 0.085
m/mol kg-1
Cd(NO2
)2
Cd(NO3
)2
CoBr2
CoCl2
CoI2
Co(NO3
)2
CsBr
0.001 0.881 0.888 0.890 0.889 0.887 0.888 0.965
0.002 0.837 0.851 0.854 0.852 0.849 0.850 0.951
0.005 0.759 0.787 0.794 0.789 0.783 0.786 0.925
0.010 0.681 0.728 0.740 0.732 0.724 0.728 0.898
0.020 0.589 0.664 0.681 0.670 0.661 0.663 0.864
0.050 0.451 0.576 0.605 0.586 0.582 0.576 0.806
0.100 0.344 0.515 0.556 0.528 0.540 0.516 0.752
0.200 0.247 0.465 0.523 0.483 0.527 0.469 0.691
0.500 0.148 0.428 0.538 0.465 0.596 0.446 0.605
1.000 0.098 0.437 0.685 0.532 0.845 0.492 0.540
2.000 0.069 0.517 1.421 0.864 2.287 0.722 0.485
5.000 0.054 13.9 55.3 3.338 0.454
10.000 196
m/mol kg-1
CsCl CsF CsI CsNO3
CsOH Cs2
SO4
CuBr2
0.001 0.965 0.965 0.965 0.964 0.966 0.885 0.889
0.002 0.951 0.952 0.951 0.951 0.953 0.845 0.853
0.005 0.925 0.929 0.925 0.924 0.930 0.775 0.791
0.010 0.898 0.905 0.898 0.897 0.906 0.709 0.735
0.020 0.864 0.876 0.863 0.860 0.878 0.634 0.674
0.050 0.805 0.830 0.804 0.796 0.836 0.526 0.594
0.100 0.751 0.792 0.749 0.733 0.802 0.444 0.541
0.200 0.691 0.755 0.688 0.655 0.772 0.369 0.504
0.500 0.607 0.721 0.601 0.529 0.755 0.285 0.503
1.000 0.546 0.726 0.534 0.421 0.782 0.233 0.591
2.000 0.496 0.803 0.470 0.859
5.000 0.474
10.000 0.508
5-106
m/mol kg–1
CuCl2
Cu(ClO4
)2
Cu(NO3
)2
FeCl2
HBr HCl HClO4
0.001 0.887 0.890 0.888 0.888 0.966 0.965 0.966
0.002 0.849 0.854 0.851 0.850 0.953 0.952 0.953
0.005 0.783 0.795 0.787 0.785 0.930 0.929 0.929
0.010 0.722 0.741 0.729 0.725 0.907 0.905 0.906
0.020 0.654 0.685 0.664 0.659 0.879 0.876 0.878
0.050 0.561 0.613 0.577 0.570 0.837 0.832 0.836
0.100 0.495 0.572 0.516 0.509 0.806 0.797 0.803
0.200 0.441 0.553 0.466 0.462 0.783 0.768 0.776
0.500 0.401 0.617 0.431 0.443 0.790 0.759 0.769
1.000 0.405 0.892 0.456 0.500 0.872 0.811 0.826
2.000 0.453 2.445 0.615 0.782 1.167 1.009 1.055
5.000 0.601 2.083 3.800 2.380 3.100
10.000 33.4 10.4 30.8
15.000 323
m/mol kg–1
HF HI HNO3
H2
SO4
KBr KCNS KCl
0.001 0.551 0.966 0.965 0.804 0.965 0.965 0.965
0.002 0.429 0.953 0.952 0.740 0.952 0.951 0.951
0.005 0.302 0.931 0.929 0.634 0.927 0.927 0.927
0.010 0.225 0.909 0.905 0.542 0.902 0.901 0.901
0.020 0.163 0.884 0.875 0.445 0.870 0.869 0.869
0.050 0.106 0.847 0.829 0.325 0.817 0.815 0.816
0.100 0.0766 0.823 0.792 0.251 0.771 0.768 0.768
0.200 0.0550 0.811 0.756 0.195 0.722 0.716 0.717
0.500 0.0352 0.845 0.725 0.146 0.658 0.647 0.649
1.000 0.0249 0.969 0.730 0.125 0.617 0.598 0.604
2.000 0.0175 1.363 0.788 0.119 0.593 0.556 0.573
5.000 0.0110 4.760 1.063 0.197 0.626 0.525 0.593
10.000 0.0085 49.100 1.644 0.527
15.000 0.0077 2.212 1.077
20.000 0.0075 2.607 1.701
m/mol kg–1
KClO3
K2
CrO4
KF KH2
PO4
* K2
HPO4
** KI KNO3
0.001 0.965 0.886 0.965 0.964 0.886 0.965 0.964
0.002 0.951 0.847 0.952 0.950 0.847 0.952 0.950
0.005 0.926 0.779 0.927 0.924 0.779 0.927 0.924
0.010 0.899 0.715 0.902 0.896 0.715 0.902 0.896
0.020 0.865 0.643 0.870 0.859 0.643 0.871 0.860
0.050 0.805 0.539 0.818 0.793 0.538 0.820 0.797
0.100 0.749 0.460 0.773 0.730 0.457 0.776 0.735
0.200 0.681 0.385 0.726 0.652 0.379 0.731 0.662
0.500 0.569 0.296 0.670 0.529 0.283 0.676 0.546
1.000 0.239 0.645 0.422 0.646 0.444
2.000 0.199 0.658 0.638 0.332
5.000 0.871
10.000 1.715
15.000 3.120
m/mol kg–1
KOH K2
SO4
LiBr LiCl LiClO4
LiI LiNO3
0.001 0.965 0.885 0.965 0.965 0.966 0.966 0.965
0.002 0.952 0.844 0.952 0.952 0.953 0.953 0.952
0.005 0.927 0.772 0.929 0.928 0.931 0.930 0.928
0.010 0.902 0.704 0.905 0.904 0.908 0.908 0.904
0.020 0.871 0.625 0.877 0.874 0.882 0.882 0.874
0.050 0.821 0.511 0.832 0.827 0.843 0.843 0.827
0.100 0.779 0.424 0.797 0.789 0.815 0.817 0.788
0.200 0.740 0.343 0.767 0.756 0.795 0.802 0.753
0.500 0.710 0.251 0.754 0.739 0.806 0.824 0.726
1.000 0.733 0.803 0.775 0.887 0.912 0.743
2.000 0.860 1.012 0.924 1.161 1.197 0.837
5.000 1.697 2.696 2.000 1.298
Mean Activity Coefficients of Electrolytes as a Function of Concentration	 5-107
m/mol kg–1
KOH K2
SO4
LiBr LiCl LiClO4
LiI LiNO3
10.000 6.110 20.0 9.600 2.500
15.000 19.9 147 30.9 3.960
20.000 46.4 486 4.970
m/mol kg–1
LiOH Li2
SO4
MgBr2
MgCl2
MgI2
MnBr2
MnCl2
0.001 0.964 0.887 0.889 0.889 0.889 0.889 0.888
0.002 0.950 0.847 0.852 0.852 0.853 0.853 0.850
0.005 0.923 0.780 0.790 0.790 0.791 0.791 0.786
0.010 0.895 0.716 0.733 0.734 0.736 0.735 0.727
0.020 0.858 0.645 0.672 0.672 0.677 0.674 0.662
0.050 0.794 0.544 0.593 0.590 0.602 0.595 0.574
0.100 0.735 0.469 0.543 0.535 0.556 0.543 0.513
0.200 0.668 0.400 0.512 0.493 0.535 0.508 0.464
0.500 0.579 0.325 0.540 0.485 0.594 0.519 0.437
1.000 0.522 0.284 0.715 0.577 0.858 0.650 0.477
2.000 0.484 0.270 1.590 1.065 2.326 1.224 0.661
5.000 0.493 36.1 14.40 109.8 6.697 1.539
m/mol kg–1
Mn(ClO4
)2
NH4
Cl NH4
ClO4
(NH4
)2
HPO4
** NH4
NO3
NaBr NaBrO3
0.001 0.892 0.965 0.964 0.882 0.964 0.965 0.965
0.002 0.858 0.952 0.950 0.839 0.951 0.952 0.951
0.005 0.801 0.927 0.924 0.763 0.925 0.928 0.926
0.010 0.752 0.901 0.895 0.688 0.897 0.903 0.900
0.020 0.700 0.869 0.859 0.600 0.862 0.873 0.867
0.050 0.637 0.816 0.794 0.469 0.801 0.824 0.811
0.100 0.604 0.769 0.734 0.367 0.744 0.783 0.759
0.200 0.596 0.718 0.663 0.273 0.678 0.742 0.698
0.500 0.686 0.649 0.560 0.171 0.582 0.697 0.605
1.000 1.030 0.603 0.479 0.114 0.502 0.687 0.528
2.000 3.072 0.569 0.399 0.074 0.419 0.730 0.449
5.000 0.563 0.303 1.083
10.000 0.220
15.000 0.179
20.000 0.154
m/mol kg–1
Na2
CO3
NaCl NaClO3
NaClO4
Na2
CrO4
NaF Na2
HPO4
*
0.001 0.887 0.965 0.965 0.965 0.887 0.965 0.887
0.002 0.847 0.952 0.952 0.952 0.849 0.951 0.848
0.005 0.780 0.928 0.927 0.928 0.783 0.926 0.780
0.010 0.716 0.903 0.902 0.903 0.722 0.901 0.717
0.020 0.644 0.872 0.870 0.872 0.653 0.868 0.644
0.050 0.541 0.822 0.818 0.821 0.554 0.813 0.539
0.100 0.462 0.779 0.771 0.777 0.479 0.764 0.456
0.200 0.385 0.734 0.719 0.729 0.406 0.710 0.373
0.500 0.292 0.681 0.646 0.668 0.318 0.633 0.266
1.000 0.229 0.657 0.590 0.630 0.261 0.573 0.191
2.000 0.182 0.668 0.537 0.608 0.231 0.133
5.000 0.874 0.648
m/mol kg–1
NaI NaNO3
NaOH Na2
SO3
Na2
SO4
Na2
WO4
NiBr2
0.001 0.965 0.965 0.965 0.887 0.886 0.886 0.889
0.002 0.952 0.951 0.952 0.847 0.846 0.846 0.853
0.005 0.928 0.926 0.927 0.779 0.777 0.777 0.791
0.010 0.904 0.900 0.902 0.716 0.712 0.712 0.735
0.020 0.874 0.866 0.870 0.644 0.637 0.638 0.675
0.050 0.827 0.810 0.819 0.540 0.529 0.534 0.596
0.100 0.789 0.759 0.775 0.462 0.446 0.457 0.546
0.200 0.753 0.701 0.731 0.386 0.366 0.388 0.514
0.500 0.722 0.617 0.685 0.296 0.268 0.320 0.535
1.000 0.734 0.550 0.674 0.237 0.204 0.291 0.692
2.000 0.823 0.480 0.714 0.196 0.155 0.291 1.476
5-108	 Mean Activity Coefficients of Electrolytes as a Function of Concentration
m/mol kg–1
NaI NaNO3
NaOH Na2
SO3
Na2
SO4
Na2
WO4
NiBr2
5.000 1.402 0.388 1.076
10.000 4.011 0.329 3.258
15.000 9.796
20.000 19.410
m/mol kg–1
NiCl2
Ni(ClO4
)2
Ni(NO3
)2
Pb(ClO4
)2
Pb(NO3
)2
RbBr RbCl
0.001 0.889 0.891 0.889 0.889 0.882 0.965 0.965
0.002 0.852 0.855 0.851 0.851 0.840 0.951 0.951
0.005 0.789 0.797 0.787 0.787 0.764 0.926 0.926
0.010 0.732 0.745 0.730 0.729 0.690 0.900 0.900
0.020 0.669 0.690 0.666 0.666 0.604 0.866 0.867
0.050 0.584 0.621 0.581 0.580 0.476 0.811 0.811
0.100 0.527 0.582 0.524 0.522 0.379 0.760 0.761
0.200 0.482 0.567 0.481 0.476 0.291 0.705 0.707
0.500 0.465 0.639 0.467 0.458 0.195 0.630 0.633
1.000 0.538 0.946 0.528 0.516 0.136 0.578 0.583
2.000 0.915 2.812 0.797 0.799 0.535 0.546
5.000 4.785 4.043 0.514 0.544
10.000 33.8
m/mol kg–1
RbF RbI RbNO3
Rb2
SO4
SrBr2
SrCl2
SrI2
0.001 0.965 0.965 0.964 0.886 0.889 0.888 0.890
0.002 0.952 0.951 0.950 0.845 0.852 0.850 0.854
0.005 0.927 0.926 0.924 0.776 0.790 0.785 0.793
0.010 0.902 0.900 0.896 0.710 0.734 0.725 0.740
0.020 0.871 0.866 0.859 0.635 0.673 0.659 0.681
0.050 0.821 0.810 0.795 0.526 0.591 0.569 0.606
0.100 0.780 0.759 0.733 0.443 0.535 0.506 0.557
0.200 0.739 0.703 0.657 0.365 0.492 0.455 0.526
0.500 0.701 0.627 0.536 0.274 0.476 0.421 0.542
1.000 0.697 0.574 0.430 0.217 0.545 0.451 0.686
2.000 0.724 0.532 0.320 0.921 0.650
5.000 0.517
m/mol kg–1
UO2
Cl2
UO2
(NO3
)2
ZnBr2
ZnCl2
ZnI2
0.001 0.888 0.888 0.890 0.887 0.893
0.002 0.851 0.849 0.854 0.847 0.859
0.005 0.787 0.784 0.794 0.781 0.804
0.010 0.729 0.726 0.741 0.719 0.757
0.020 0.666 0.663 0.683 0.652 0.708
0.050 0.583 0.583 0.606 0.561 0.644
0.100 0.529 0.535 0.553 0.499 0.601
0.200 0.493 0.509 0.515 0.447 0.574
0.500 0.501 0.532 0.516 0.384 0.635
1.000 0.601 0.673 0.558 0.330 0.836
2.000 0.948 1.223 0.578 0.283 1.062
5.000 3.020 0.788 0.342 1.546
10.000 2.317 0.876 4.698
15.000 5.381 1.914
20.000 7.965 2.968
*	 The anion is H2
PO4
–
.
**	The anion is HPO4
–2
.
Mean Activity Coefficients of Electrolytes as a Function of Concentration	 5-109