0. J. KLEPPAAND M.
1120
experimental activation energy.31 Table V1I lists these quantities calculated from the experimental data. Because of the uncertainties in the experimental data, the activation quantities are probably reliable to about a factor of 2. TABLE VI1 THERMODYNAMIC ACTIVATION VALUES Reaction
p,, + ++-pu + + + + PLI+++-Pu( OH)+++
AEew
AS**=,
(e.u.)
(kcal./mole)
7.7 2.8
-31
18
(kcal./iriole)
-32
AFfxp
12
Discussion It is felt that the competing bimolecular reactions indicated in eq. 1 and 2 are the best possible representation of the plutonium exchange system a t the stated conditions. Except that the rate of exchange is much greater in this system, i.e., some 100-1000 times as fast as the Fe(I1)-Fe(II1) exchange, the plutonium reaction generally is analogous to others involving simple cations. Although the experimental data were treated in a statistically rigorous manner, the discrete values of the rate constants and energy values are somewhat uncertain. This rapid exchange system did not lend itself t o precise measurements. For example, at plutonium concentrations of Pu(II1) = Pu(1V) = 5 X 10-Efin 1fHCIOl a t 25", the halftime for exchange is 0.68 minute. So-called (31) S. Glasstone, I
