AbstractThe complexation of the Cu2+ ion with 2‐Hydroxybenzamide (salicylamide, HL) has been studied, at 25 °C, by potentiometric measurements with a glass electrode in NaClO4 media for ionic strength ranging from 0.5 to 3 mol/dm3. The data are consistent with the formation of the complexes CuH‐1(HL)+, CuH‐2(HL)2, Cu2H‐2(HL)22+ and CuH‐2(HL). The minor species, Cu2H‐2(HL)22+ and CuH‐2(HL), amount to at least 20% of the total copper.Elaboration of the data according to the Specific Interaction Theory yields the constants valid in the infinite dilution reference state:   HL ⇌ L‐ + H+ log °β011 = ‐ 8.27 ± 0.03 Cu2+ + HL ⇌ CuH‐1(HL)+ + H+ log °β111 = ‐ 3.06 ± 0.05 Cu2+ + 2 HL ⇌ CuH‐2(HL)2 + 2 H+ log °β122 = ‐ 7.72 ± 0.05 2Cu2+ + 2HL ⇌ Cu2H‐2(HL)22+ + 2 H+ log °β222 = ‐ 5.5 ± 0.1 Cu2+ + HL ⇌ CuH‐2(HL) + 2 H+ log °β121 = ‐ 10.9 ± 0.1 and the interaction coefficients (kg/mol) of complex species with medium ions: b(L‐,Na+) = 0.11 ± 0.03; b(CuH‐1(HL)+,NaClO4) = 0.17 ± 0.05; b(CuH‐2(HL)2,NaClO4) = 0.11 ± 0.05; b(Cu2H‐2(HL)22+,NaClO4) = 0.27 ± 0.1; b(CuH‐2(HL),NaClO4) = ‐ 0.03 ± 0.1.