Pu solutions

Figure 1. Percent Pu(IV) polymer vs. time for 0.05 M Pu solutions at 50°C. Solid/dashed lines—solutions with/without 0.05 M U02(N0o)2 added. Makeup HNO concentrations for solutions are indicated. (Reprinted with permission from Ref. 2.)...

The gifted chemists who worked on the "Manhattan Project" recognized and attempted to quantitatively describe the effects of a self-radiolysis soon after the preparation of macroscopic quantities of 239Pu. The present symposium provides an appropriate time and place to cite a number of these individuals for their contributions to an important aspect of Pu solution chemistry. 

Plutonium dissolved in HCl giving blue Pu" solutions which, on treatment with base, afforded Pu(OH)3. Reaction of this with formic acid gave the blue Pu(02CH)3, isomorphous with Gd(02CH)3, which, on heating in air, decomposed into PUO2. 

Electrodeposition of Pa metal has been performed from both aqueous and nonaqueous solutions. An isopropanol solution of 10-20 p,gmL Pa from 8M HCl/0.01 M HE/Pa stock was employed for quantitative electrodeposition [41]. The cell consisted of a gold-plated A1 cathode and a Pt wire anode. During deposition the current was maintained at 1 mA, which produced a potential of 400-600 V during the 90-min electrolysis. The progress of the electrolysis was externally monitored by alpha-counting of the electrolysis solution before and during the electrodeposition. Deposition studies of metal from aqueous solutions are more common. Pa was electrodeposited on platinum in 95% yield at tracer concentrations from an electrolyte of [NH4]C1/HC1 [42]. Electrochemical and chemical conditions of the plating process were described for Pu solutions, which served as a model for the other actinide elements studied. Another tracer... 

On top of the PU solution the same quantity of PAN solution was poured with great care to prevent emulsification at the liquid interface. Thermodynamic equilibrium between the two phases was unlikely. After three days the volume of the PU phase had decreased by about 5%. After the solution had stood for eight days, the two layers were separated, and the different emulsions were prepared by vigorous stirring of different proportions of the two liquids. The emulsions thus obtained were stable for at least one day. 

Figure 1. Difference in deformability between a PAN droplet in a PU solution (A, C) and a PU droplet in a PAN solution (B, D) at corresponding shear rates...

Figures 4 and 5 represent the viscosities of the emulsions measured with a falling-ball viscometer. When one ball is used (a steel ball 0.8 mm in diameter), only one value of the viscosity is measured for each emulsion and not a flow curve. The emulsions in Figure 4 are rich in PU solution, and those in Figure 5 are rich in PAN solution.

Figure 5. Measurements with a falling-ball viscometer. Ratio between viscosities of emulsions and matrix vs. volume fraction of dispersed PU solution.

For a steel ball 0.8 mm in diameter this average shear stress is about 100 dynes/cm2. Referring to Figure 1 we see that at this shear stress PAN droplets in a PU solution are spherical and that PU droplets in a PAN solution are highly deformed into oblong bodies. Thus, it may be expected that only the dispersed PAN emulsions will conform to Taylors law (Figure 4) and not the dispersed PU emulsions (Figure 5). Our observations confirmed this. 

The calculations were carried out for a shear stress at the wall of 2 X 104 dynes/cm2. The two values for ftaPP and their average were plotted together with the results from the measurements (Figure 3) against the volume fraction of the PAN solution in Figure 9. The calculated mean viscosity line coincides with the measurements on the emulsions that are rich in PU solution. On the other hand, for PAN rich... 

---