A SPECTROPHOTOMETRIC STUDY OF THE HYDROLYSIS OF PLUTONIUM(IV)

The hydrolysis of Pu(IV) in H/sub 2/O and D/sub 2/O was studied by means of spectrophotometric measurements at 3300 A and various acidities. The data were solved with the least squares method on an IBM computer (704) for the hydrolysis constant K = STAPuOH/sup 3+/!STAH/sup +/!/STAPu/sup 4+/!. Measurements were made at 15.4 and 25.0 deg C, and they give 8.5 plus or minus 0.9 and 19.4 plus or minus 1.3 kcal/mole for the heat of hydrolysis in H/sub 2/O and D/sub 2/O, respectively. For an ionic strength of 2 M and 25.0 deg C, the weighted K ia 0.0185 plus or minus 0.0004 in H/sub 2/O and 0.0115 plus or minus 0.0008 in D/sub 2/O. This is given a K/sub H//K/sub D/ of 1.6. which is in disagreement with that found from kinetic studies of the Pu(III)Pu(VI) reaction, but in qualitative agreement with the K/sub H//K/sub D/ ratios observed for Np(IV) and U(IV). The K/sub H/ is compared with the values derived from earlier spectrophotometric data for Pu(IV) and potentiometric data for the Pu(III)-Pu(IV) couple. (D.L.C.)