AbstractpK a(NH 3+)values ofN,N‐dihydroxyethylglycine (bicine) andN‐[tris(hydroxymethyl)methyl]‐glycine (tricine) have been determined by the Irving‐Rossotti method in an aqueous medium at 25, 30, 35, 40, 45, and 50°C and at different ionic strengths (I= 0.1, 0.5, and 1.0). Plots betweenpKa(NH 3+) and 1/Tfor various ionic strengths have been obtained and the values of slopes have been used to calculate the ΔH, ΔS, and ΔGfor the dissociation reactions of bicine and tricine. The ΔH, ΔS, and ΔGvalues for bicine were found to be 10.6 ± 0.6 kcal mol−1, −1.9 ± 1.8 e.u., and 11.1 ± 0.06 kcal mol−1, respectively, and for tricine 11.2 ± 0.6 kcal mol−1, 1.6 ± 1.6 e.u., and 10.7 ± 0.06 kcal mol−1, respectively. ThepKa(NH 3+) values decrease with rise in temperature but the influenc