POLAROGRAPHIC INVESTIGATION OF THE SYSTEMS ARSENIC(III)-TARTARIC ACID AND ARSENIC(III)-1,2-DIAMINO-CYCLOHEXANE-N,N,N′,N′-TETRAACETIC ACID (DCTA)

Abstract

The reactions between As(III), tartaric acid (H₂T)and DCTA were investigated polarographically. The conditional stability constants of As(III)-complexes at a given pH-value and variable ligand concentration were calculated from the change of the limiting currents. The optimum conditions for calculating stability constants from the current were also discussed. It was found that DCTA (H₄L)formed the complex [As(OH)₂HL]^2- whose overall formation constant was lgβ111=(20.67 ±0.09)atμ=0.1 and t°- (25.0±0.2)°C, whereas the complex between As(III) and H₂T was [As(OH)₂T]⁻ with an overall stability constant 1gβ 101= 6.62 ±0.14 at μ=0.1 and t°= (25 ± 0.2)°C.