2'14
ANALYTICAL CHEMISTRY
mot'or and to drive any corrosive fumes away from the unit. Safety covers are mounted over both the fan and the chain drive. The carriage shaft is carried by two roller bearings. The carriage assembly is fastened to the end of the drive shaft by a brass flange and is made of two 3/8-inch asbestos cement disks, 57/8 inches in diameter, which are separated by a ll/n-inch brass insert 1 inch in diameter. Eleven semicircular sectors, 3/( inch in diameter, have been cut out of the circumference of the disks a t equal intervals. Eleven steel posts ( I / * X 1 3 / r inches) are fastened with silver solder on the brass insert in a line with the 11 semicircular sectors. A curved test tube clamp, 6 / * inch wide, fashioned from l/sp-inch sheet stainless steel is fastened to the end of the 11 posts with silver solder. The motor, gears, and carriage are mounted on an aluminum plate (see Figure 1) t h a t is fastened to the chassis by a pianotype hinge placed under the chain-drive assembly. A thumbscrew a t the opposite end of the plate allows the entire unit to be rotated about the hinge to 20 degrees from the horizontal and thus permits the closed end of the test tube to be depressed into the furnace unit. TWO flat brass ways, X 1 1 / 2 inches, on the underside of the furnace are fitted to two T-shaped aluminum ways fastened to the chassis, providing tracks on which the furnace moves. The furnace is constructed from 0.5-inch asbestos cement board and is assembled with machine screws. Figure 2 illustrates interior design and Figure 1 gives dimensions. A curved slot is cut in the back wall of the furnace t,o permit the entry of the carriage when the furnace is moved toward the motor and gear assembly. Twenty holes, inch in diameter, are drilled along the lov,-er edges of the sides and front of the furnace to furnish sufficient ventilation for the gas burners. Five high-temperature natural gas-type burners, whose bases have been cut to permit close assemblage, are connected t o a copper manifold by short lengths of rubber tubing. The burners can be regulated in the normal manner and cau be removed easily for occasional cleaning. The front of the furnace is a door held by two piano-type hinges 1.5 inches in length and fastened by a hook and eye. A projecting handle is plac.ed on the door t o facilitate moving the furnace. is made of Ixird pine painted r i t h heat-rcsist:int 1not:il paint.
takes a t least 4 hours-and requires a special apparatus and equipment. This paper reports an electrolytic oxidation method for plutonium which is faster and simpler than ozonation and is still quantitative and exclusive of foreign ions. APPARATUS
The electrolysis apparatus is similar to that described by iMiller and Brouns, except that a polyethylene bottle and screw cap without gaskets are used for the electrodeposition cell. The cathode is a platinum wire coated with paraffin, except for an area of approximately 0.033 sq. cm. a t the tip. PROCEDURE
The plutonium solution is transferred to the assembled electrodeposition cell and made 0.5N in perchloric acid and 10 ml. in volume. A 20-sq. cm. platinum anode is rotated to produce vigorous stirring. The platinum mire cathode is placed in the cell, and a current of 60 ma. is passed through the solution for 15 minutes. The plutonium is 98% oxidized a t the end of this time as determined by lanthanum fluoride carrying of plutonium(II1) and ( I T ) . If electrodeposition is desired, sodium hydroxide iadded to adjust the hydroxide ion concentration and the deposition is performed as described by hIiller and Brouns. RESULTS
.
A perchloric acid concentration of 0.531 was found to be the optimum for the oxidation (Table I). A current of at least 30 ma. was required for efficient ovidation a t a 5-sq. em. anode Decreasing the anodic current density increased the plutonium oxidation efficiency as shown in Table 11. Plutonium was 98% oxidized a t 3 ma. per sq. em. The oxidation is essentially complete in a matter of minutes. Microgram quantities n ere 98% oxidized in I O minutes, milligram amounts in 15 (Table 111).
OPERATIOS
The fiisiou is accoinpli~hrdin tht, miiltiple-unit fmion rack as follow:
Table I. Effectof Perchloric Acid Concentration on Anodic Oxidation of Plutonium
The position of the furnace and the carriage a t the beginning of the fusion is.shown in Figure 2. Eleven 16 X 150 mm. borosilicate glass test tubes cont,aining the samples of soil or rock mixed witl? an appropriate flux are placed around the periphery of the carriage. The carriage is adjusted by the thumbscrew to lower the bottom end of t,lie test tubes, and the motor is started. The buruers are then lighted and the furnace is pushed under the revolving test tubes. After the fusion is completed, the furnacr is withdrawn from the carriage, which is then adjusted to support the test tubes in a horizontal position. The unit is allowed to rotate until the melt has solidified o n the sides of the test tubes in :I thin laye:.
(65 ma., 5-sq. em. P t anode, 0.5 y of plutonium, 1-how electrolysis)
While the fusion process is taking place, the operator is free t,o utilize his time on another operation, thus cutting doxn greatly the number of man-hours spent iii making a large number of test tube fusions.
PI,
HCIOI,
M
55
0.1 0.2 0.25
88
88 ~. 92 78 72 50
0.5 1.0 2.0 4.0
Table 11. Effect of Anodic Current Density on Electrolytic Oxidation of Plutonium Pu
Taken for Oxidation 1.5?
P u r l ~ r c a ~ i authorized ns by the Director, 11,S. Geological Survey.
(60 ma., 0.5.W HClO,, I-hour electrolysis) Pi1 Anodic Current Oxidized, Density, Ma./Sq. Cm. % 30 72.0 15 91.3 6 97.0 3 97.8 1.5 97.2
1 .5 m g .
6 3 1 5
97.5 97.8 99.0
Electrolytic Oxidation of Plutonium Roy KO, General Electric Co., Hanford Atomic Products Operation, Richland, Wash.
quantitative electrodeposition of plutonium by the method of Miller and Brouns [Miller, H. W., and Brouns, K. J , A.v.4~.CHEM.24, 536 (1982)],in which Pu(V1) is reduced cathodically in n potassium hydroxide solution and deposited as Pu( OH)4> the metal must be in the sexivalent state. The most suitable oxidation method has been ozoriation ( AIiller and Brouns), which ovidizes plutonium quantitatively without introducing ions which interfere in the electrodeposition. Ozonation, howevcv, i 4 slow-the oxidation of milligram amounts of plutonium OR
F
Table 111. Effect of Time on Anodic Oxidation of Plutonium Pu
Taken for Oxidation 1.5 y
1.5 mg.
(3 ma./sq. cm., 0.5.W HClOd Time of Oxidation, Min. 5 10 15
30 60 10 15 30 GO
Pu
Oxidized, 76
85.6 97.8 RB.9 96.7 97.8 95.4 98.3 98.6 99.0
