Abstract
Polarographic behaviour of arsenic(III) has been investigated in sulfuric acid of various concentrations (6.0M14.4M).
Arsenic(III) gives a three-step wave in 6.0M to 13.0M sulfuric acid, and a one-step wave in 14.4M sulfuric acid.
The second and the third steps of the former wave are distorted by a sharp maximum, which can be sup-pressed with 0.02% Triton X-100.
The limiting currents of the first and the second steps of the former wave, and of the latter one-step wave are controlled by the diffusion. They are directly propor tional to the concentrations of arsenic(III) in the range of 2×10-4M to 1.8×10-3M.
On increasing the concentration of sulfuric acid, the half-wave potential of arsenic(III) is shifted toward the positive side and then the limiting current decreases gradually. This decrease of the limiting current is attributed to the increased viscosity of sulfuric acid. The amount of the decrease obeys the Stockes-Einstein equation.
The use of 14.4M sulfuric acid is recommended for the microdetermination of arsenic in its concentration ranee of 2×10-4M to 1.8×10-3M.
