Dissociation of arsenious and arsenic acids

H3As03S H3AsO3S0 H2As03S + 25 3.3 Thilo, Hertzog and Winkler (1970) Schwedt 

Following Equation 2.23, the dissociation constant for Reaction 2.41 is further described as follows  

Like pH and pA Sp, any dissociation constant may be conveniently written as a p/fa value, where p/fa = —log10 A a. That is, the p/fa of Reaction 2.41 at 25 °C and 1 bar pressure is about 9.2 (Table 2.10). Furthermore, like pH, p/fa values are often sensitive to temperature. In hydrothermal waters, for example, the pA a value of Reaction 2.43 declines with increasing temperature so that the value approaches 7.11 at 300 °C (Zakaznova-Herzog, Seward and Suleimenov, 2006), 1936 Table 2.10. 

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