Polarographic studies of indium(III) in aqueous medium of sodium azide

Abstract

Abstract:In this paper, some aspects of the polarography of indium(II1) in azidelhydrazoic acid buffer are presented. The electrode process is mostly governed by diffusion in the complexing medium. Nevertheless, for controlled-potential coulometry (involving a large time window) a catalytic process was observed, ascribed to the reaction of the hydrazoic acid and indium amalgam. The stability of azide complexes of In(II1) was studied polarographically, and the formation of four mononuclear species was confirmed by computational analysis of data obtained from polarograms of In(II1) in different azide concentrations. The values of the global constants obtained are: PI = 3.7 x 10' M-', P2 = 8.6 x lo5 M -~, P3 = 5.0 x lo7 M -~, P4 = 2.1 x lo9 MA, in a constant ionic strength medium held at 2.0 M with NaC10,. These data are in good agreement with those obtained by potentiometry. The value found for E ' of the In(III)/In couple was -5 12.2 mV vs. calomel electrode (3 M NaCl), the mean diffusion coefficient of the complex being (6.1 ? 0.2) x 10-~cm' s-I in perchlorate medium (T = 25OC).Key words: polarography, indium(II1). azide, stability constants, catalytic wave Resum6 : Dans ce travail, on prCsente quelques aspects de la polarographie de l'indium(II1) dans un tampon d'azoturelacide hydrazoi'que. Le processus B 1'Clectrode est principalement dCterminC par la diffusion dans le milieu complexant. Toutefois, pour la coulomCtrie B potentiel contr61C (impliquant une large fenstre de temps), on a observt un processus catalytique attribuC B la rCaction de I'acide hydrazoi'que avec l'amalgame d'indium.Faisant appel a la polarographie, on a CtudiC la stabilitC des complexes d'azoture avec le In(II1) et on a confirm6 la formation de quatre espbces mononuclCaires par une analyse mathkmatique des donnCes obtenues B partir de polarogrammes du In(II1) B diverses concentrations d'azoture. Les valeurs des constantes globales obtenues sont : p = 3.7 x 10' M-I, P, = 8,6 x 10" M-', P, = 5,O x lo7 M-? el P, = 2,l x lo9 MA, B une force ionique constante maintenue B 2,O M par du NaCIO,. Ces donnCes sont en bon accord avec celles obtenues par potentiomCtrie. La valeur trouvCe pour EO' dans le couple In(II1)IIn est de -5 12,2 mV vs. Clectrode au calomel (3 M NaCI) alors que le coefficient moyen de diffusion du complexe est (6,l ? 0.2) x 10" cm2 s-I dans un milieu de perchlorate (T = 25OC).

Nucleation Process of Indium on a Copper Electrode

“…However these values are quite different from those (~10 −6 cm 2 s −1 ) obtained by Valderrama et al. 15) According to Tokoro et al 20) the diffusion coefficient of the In 3+ complex in aqueous medium of azide which acted as a catalytic ligand was around 6.1×10 −6 cm 2 s −1 . For the reduction of indium complex the electron transfers from the electrode to metal ion occurred through a ligand bridge.…”

“…[17][18][19] The reduction of In 3+ in a complex requires more negative potential due to the stability via complexation. 20) We carried out cyclic voltammetry of indium under noncomplexing circumstance of an acidic solution containing 5 and −0.14 V vs. SHE, respectively. 21) It is considered that in the potential range from −0.55 V to −0.75 V, In 3+ is reduced according to the reaction (25) and/or a sequential reaction of reactions (26) and (27):…”

Nucleation Process of Indium on a Copper Electrode

“…[17][18][19] The reduction of In 3+ in a complex requires more negative potential due to the stability via complexation. 20) We carried out cyclic voltammetry of indium under noncomplexing circumstance of an acidic solution containing 5 × 10 Fig. 1 shows that in the forward scan of negative direction, the current densities increase slowly in the potential range of −0.15 V ≥ E ≥ −0.55 V and increase rapidly in the potential range of −0.55 V ≥ E ≥ −0.75 V. In the potential range from −0.15 V to −0.55 V, increase of negative current density does not indicate the metallic depositing of indium.…”