抄録
Since a greater part of 51Cr discharged into the sea is considered to be present mainly in the valence state of VI, it was reduced to Cr(III) by iron(II) and collected by the ferric hydroxide coprecipitation method. The carrier of chromium (0.09 mg) was added to 50 ml of sea-water containing tracer 51Cr and the pH of the mixture was brought to 1.8 by the addition of hydrochloric acid. A solution of iron(II) sulfate (0.6 mg Fe) was added to reduced Cr(VI) and then the mixture was adjusted its pH at 8 to precipitate hydroxides with sodium hydroxide after the addition of 2.25 mg of iron(III) as a collector. 51Cr was collected rapidly and quantitatively as hydroxide. The procedure has been also proved to be satisfactory in a larger scale operation (80 fold). Several other radioisotopes such as 54Mn, 59Fe, 60Co and 65Zn were also coprecipitated quantitatively and it was found to be advantageous in the separation of chromium from the hydroxides precipitates that the reducing agent and the collecting agent are the same, material, iron.
