Fig. 4
Evolution of conductivity and pH, monitoring the reaction of Eq. (4) when subjected to a variation in H or Case. (a) Evolution of \(\sigma ^{\mathrm{Eq.4}}_{\text{i} }\)(H, Case) (i = 1 to 4, H = 0.0, 8.0kOe,Case = I-case, M-case). Within the range preceding the addition of \({\text{CaCl}}_{2\mathrm{(aq)}}\), \(\sigma\) must be constant. Accordingly, the observed linear-in-time variation must be related to a linear-in-temperature evolution, driven by the Joule conversion of the mechanical work of P1 pump (see Fig. 2). On subtracting this thermal effect and normalizing to \(\sigma _{25 ^{\circ }{\text{C}}} \equiv \sigma ^{\mathrm{Eq.4}}_{\text{i} }\mathrm{(H, Case, 25}^{\circ }\mathrm{C)}\), we obtained (b) the evolution of \(\sigma ^{\mathrm{Eq.4}}_{\text{i} }\)(H, Case) (i = 1 to 4, H = 0.0, 8.0kOe, Case = I-case, M-case). The thick solid blue line emphasizes the linear rise of \(\sigma ^{\mathrm{Eq.4}}_{\text{i} }\)(H, Case) (see text). (c) Evolution of \(\text{pH} ^{\mathrm{Eq.4}}_{\text{i} }\)(H, Case) (i = 1 to 5, H = 0.0, 8.0kOe, Case = I-case, M-case). The thick solid blue curve simulates the exponential decay of \(\text{pH} ^{\mathrm{Eq.4}}_{\text{i} }\)(H, Case) as expressed in Eq. (7). (d) Evolution of the rate of the controlled addition of \({\text{CaCl}}_{2\mathrm{(aq)}}\) to the circulating \(\text{Na}_{2}\text{CO}_{\mathrm{3(aq)}}\) solution.
