Pulse radiolysis of Hg(CN)2 in aqueous solutions

The reduction of Hg(CN)2 in deaerated aqueous solutions was studied by the pulse radiolysis technique. Hg(CN)2 reacts with the esub(aq) with k(esub(aq)+Hg(CN)2)=(1.3+-0.1)x1010 M-1 s-1 to yield a transient species of HgCN having an absorption maximum at 285 nm. Hg(CN)2 is also reduced by CO2- with k(CO2-+Hg(CN)2)=(3.4+-0.2)x109 M-1 s-1. The extinction coefficient of HgCN at 285 nm was determined as (3.8+-0.1)x103 M-1 cm-1. HgCN recombines with 2k=(3.4+-0.5)x109 M-1 s-1 to produce another absorption species, assigned as (HgCN)2, in an unstable state. The decay rate of the dimer was accelerated by some additives, such as alcohols and sodium formate. Making use of a proposed mechanism, (HgCN)2→Hg(aq)+Hg(CN)2, the absorption coefficient of atomic mercury in water was evaluated as (2.8+-0.1)x103 M-1 cm-1. (auth.)