(a)

(b)

(c)

(d)

Figure 1: The versus pH relationships ((9), (10)) plotted for different sets of (, , pH0) values: (a) (2, , 5); (b) (2, , 7); (c) (3, , 3); (d) (3, , 6). The values are indicated at the corresponding curves. For further details, see text.