Thermodynamic constants of N-[tris(hydroxymethyl)methyl-3-amino]propanesulfonic acid (Taps) from the temperatures 278.15 K to 328.15 K

Values of the second thermodynamic dissociation constant pK2 of N-[tris(hydroxymethyl)methyl-3-amino]propanesulfonic acid (Taps) have been determined at twelve temperatures from 278.15 K to 328.15 K including 310.15 K by measurements of the electromotive-force for cells without liquid junction of the type: Pt|H2 (g, p∘ = 101.325 kPa)|Taps (m1), NaTapsate (m2), NaCl (m3)|AgCl|Ag, where m denotes molality. The pK2 values for the dissociation of Taps are represented by the equation: pK2 = 2969.61 · (K/T) – 17.05052 + 2.73697 · ln(T/K). The values of pK2 for Taps were found to be (8.502 ± 0.0007) at T = 298.15 K and (8.225 ± 0.0009) at T = 310.15 K, respectively, indicating thereby to be useful as buffer solutions for pH control in the region 7.4 to 8.5. The thermodynamic quantities, ΔG∘, ΔH∘, ΔS∘, and ΔCp∘ dissociation process of Taps have been derived from the temperature coefficients of the pK2.