The distribution of the valence states III and V of radioactive ⁷⁶As after neutron irradiations of thioarsenic compounds has been investigated. The irradiated compounds were thioarsenites as well as sodium thioarsenate; fresh precipitated arsenic trisulfide was also investigated. Materials were irradiated with neutrons at a flux of 10¹² n cm^-2 s^-1. The radioisotope formed by (n, γ) reaction is ⁷⁶As with T_1/2= 26.4h. Separations of valence states were performed by high voltage electrophoresis at a gradient of 35V cm^-1 on 3MM Whatmann paper. Radiochemical yield of As(V)in the hydrated thioarsenites was very high but when dehydrated thioarsenite is irradiated, the yield of the radioactive As(V) was much lower and similar to that obtained in the irradiated disordered trisulfide. On irradiated thioarsenate the retention was also very high. These yields are like those found in the previous work on irradiating As sulfides and it seems to be related to the covalent character of the As-S bond; likewise, internal conversion accounts for the primary oxidation of recoil atoms.

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