colors observed in electrolytes allowed to freeze in the cell while a direct current potential is maintained. T h e electrolyte is green near the anode and brown near the cathode, regardless of the relative positions of the electrodes. These are the colors that quadri- and trivalent uranium exhibit in their respective solid solution with BaF, (7. 2) (x-ray examination of the electrolyte shows the BaF?-UF4or BaF?-UF3 solid solution and the BaFy-LiF compound.) T h e cyclic reaction mechanism accounts for the relatively lo\v current efficiency obtained in laboratory cells. since a considerable portion of the current is unproductively consumed in the cycle. This mechanism also explains the observed effects of uranium content and current-on-current efficiency. Optim u m efficiency Lvould be expected kvhen the supply of electrons a t the cathode (the cathode current density) is large compared with the supply of uranium ions, in agreement with the observed increase in efficiency tvith increasing current and decreasing U F 4 concentration. Decreasing the cathode surface area by maintaining a crust of frozen electrolyte on the cell walls? as is done in aluminum reduction cells, or increasing the anodecathode spacing should improve current efficiency. However. the scale of operation, so far: makes it difficult to use spacings of greater than about 0.75 inch or to maintain a frozen salt crust on the cell walls. Considerable improvement in current efficiency is expected on larger scale operation. Both the basket and bare anode cell designs give satisfactory performance. T h e basket anode? however, has the advantage of higher throughput for a given cell size because of the higher anode surface area. -4node surface area is the factor limiting the maximum current that can be used. If the anode current density is too high, the so-called .'anode effect" results from the formation of a n insulating fluorocarbon film over the surface of the anode and interrupts the current. T h e basket anode also has other advantages over the bare anode cell: Mechanical properties of the UOu-carbon mixture are less important; carbon deficiency is less disastrous to metal quality; and scrap metal can be recycled directly to the cell. Uranium tetrafluoride is not reduced via anodic discharge of CF4 (Reaction 4) with the bare anode cell. TVhen a graphite basket is used. the reaction occurs to an appreciable extent. leading to erosion of the basket and depletion of UF4 from the electrolyte. Several means of lowering the rate of CF1 formation (and hence, lowering basket erosion) have been found. These include: T h e CFd content of the OPERATIOX AT REDUCED RATES. off-gas dropped from 15% to 6% when the current was lowered to 60% of the maximum possible. (The maximum
These measures reduce or eliminate CF4 formation and basket erosion but do so a t the expense of throughput. This is also true of the bare anode; CFI formation and basket erosion are eliminated but the throughput is lower. \Vhich of' the t\\o anode arrangements \till prove better \vi11 depend on development i t ork now in progress. Conclusions
T h e technical feasibility of a process for reduction of uranium oxides to massive uranium metal has been demonstrated in the laboratory. This process offers the advantages of loiv material costs (1 IO 2 k\v.-hr. of electricity and 0.13 pound of pirch per pound of uranium). continuous operation, high purity product. high yield (virtually 100% for a continuous process), and simple recycle of scrap metal from fabrication steps. Although many problems remain to be solved. this process is attractive as a replacement for the present conversion of CO: to CF, and batch reduction of the CF, i\-ith magnesium. .ipplication of this approach to the preparation of other reactive metals also appears feasible. literature Cited
\V. M., Ferguson. .J. F.. J . Chpm. Soc. 1959, 3401. (2) D'Eye, R. \V. M , , Martin. I;. S., Ibid..1957, 1847. (3)/ , n Driggs. F. H.. Lilliendahl. \V. C., ISD. Esc. CHEN.22, 516 ln\
(1) D'Eye. R. \I YJW).
(4) Gesellschaft zur Verwertung Chemischer Technicher Vrrfah-
ren, French Patent 830,063 (1939): 49,714 (1942). (5) Harrington, C. D.. Kuehle. A. E.. '.Uranium Production Technology." pp, 214-86. Van Sostrand. Princrton. 1959. (6) Higgins. J. K.. Bellamy. R . G.. Buddery. .J. H.. - T h e Anodic Chlorination of Bervllium Oxide in a Fused Salt Bath." L-. K. .Atomic Energv Resrarch Establishment. Harwell. Rrrks. AERE M/R 2750 (Decrmbrr 1958). (7) Marden. .J. \V., Lilliendahl. \ V . C . , Mrister. G.: Nagv. R . . \\-roughton. 0. M.. Rrcsr. S.C.. L-,S. . 4 t C Rept. AECD 3687 i~. Tiin? 1946). ., ., .
(8) Zbid..pp. ' 8 - 8 3 . 161, (9) Moissan. H.. Compt. rrnd. 113. 2 (1891). (10) Kiedrnch. L. I V . . Draring. €3. E.. .I. El~c/rorhrm.Soc. 105, ' 353 (1958). (11) Slatin. H.. Gorr. J . K.. Kolodnry. M.. Seegmiller. R . ,
\Valter. 7 . .C . S. AEC Rrpt.. LA 1056 (Frbruary 1950). M. V.. Pal'cruev. S . F.. Krasnov. YLI, N..Zhii,. Prikind. A'him. 31, 226 (1958). (13) Swarts. E. L.. Trans. ,4m. Inst.. .\dining 11'Iet. Petroi. En,ors. 215, 553 (1959). (12) Smirnov.
RECEIVED for review October 4. 1961 ACCEPTED January 19, 1962 Division of Industrial and Enqineering Chemistry, 138th Meeting. ACS. New York. September 1960. This work was supported bv the U. S. .\tomic Energv Commiqsion Contract No. \V-14-108Eng-8.
possible current flow is limited. for any particular cell design, by the onset of anode effect.) OPERATION WITH THE TIAL, Application of 9
BASKETPASSIVATED BY A HIGHP O T E N to 12 volts d.c. to the basket leads to
the formation of a passive fluorocarbon film on the basket and virtually eliminates C F 4 formation. T h e UO?-carbon material in the basket is not passivated and remains a t 4 volts relative to the cathode. However, over-all metal production rates using this approach are only about half those obtained in normal operation. O P E R A T I O N WITH THE C U R R E N T SUPPLIED TO THE .&SODE THE BASKET. This reduces THROUGH GRAPHITE RODSINSIDE
C F 4 formation by giving a smaller surface area of positively charged graphite. Furthermore, graphite erosion is confined t o relativel1. inexpensive graphite rods rather than baskets.
212
I&EC PROCESS DESIGN A N D DEVELOPMENT
Correction
23-D I M ETHY LPI PERAZ I N E SYNTHESIS FROM ISOPROPANOLAMINE I n this article by Tt'. K. Langdon, It', \V. Levis, Jr.. and D. R . Jackson [IsD. E N G . CHEM. PROCESS DESICSDEL'ELOP. 1, 153 (1962)]. on page 153. Figure 3, the amount of catalyst above the last three bars should be 1.3 G. 'MOLE instead of 2 . 3 G . 1IOLE.
