V O L U M E 2 7 , NO. 10, O C T O B E R 1 9 5 5 used is -0.54 volt us S.C.E. This value does not vary with the tin concentration over the range of concentrations listed in Table I. I n all cases the half-wave potentials are well within the range of -0.53 to -0.56 volt us. S.C.E. The half-wave potential increases to more negative potentials as the hydrogen ion concentration decreases. Although this procedure has been developed for the analysis of tin ores, there is no reason to suppose that it could not be applied to tin alloys and other tin-containing materials; especially when the tin concentration is small and there are a large number of interfering ions. Over 200 various tin ores containing 0.01 to 10% tin have been analyzed with a standard deviation always less than 2y0. An average time for one analysis is less than half an
1559
hour on a routine basis and under 2 hours for one complete analysis. LITERATURE CITED
(1)
Alimarin, I. P.. Ivanov-Emin, B. N.,and Pevsner, S. AI., 7 r i i d u
Vsesoyuz. Konjerents. And. Khim., 2, 471 (1943). ( 2 ) Allsopp, W. E., and Damerall, V. R., AKAL.CHEM.,21, ti77 (1949). (3) Kolthoff, I. AI., and Lingane, J. J., “Polarography,” 2nd ed., g . 523, Interscience, Xew York, 1952. (4) Lingane, J . J., IND. ENG.CHEM.,~ N A L ED., . 18, 429 (1916). (5) Lingane, J. J., J . Am. Chem. Soc., 67, 919 (1945). (6) Meites, L., and Meites, T., ANAL.CHEM.,20, 984 (1948). (7) Wilkie, J. RI., Chem. S e w s , 99, 311 (1909). RECEIVED for review .\larch 28, 1955.
.4ccepted June 23, 19.G
Polarography in Molten Ammonium Formate E. L. COLICHMAN1 California Research and Development
Co., Livermore, Calif.*
A wide variety of inorganic compounds has been investigated polarographically in molten ammonium formate at 125’ C. Among the compounds studied were uranium, thorium, and plutonium, as well as typical fission products such as zirconium and the rare earths. Possible applications to qualitative and quantitative analyses of both water-soluble and water-insoluble inorganic compounds are suggested by the polarographic results obtained. Results indicate the relative ease of reduction of the various ionic species in the molten ammonium formate system under the conditions prevailing in this investigation.
In the present investigation, molten ammonium format e W A S chosen as the solvent-supporting electrolyte system, as it afforded the advantage of an operating t,eniperature of 125’ C., whirh permitted use of a dropping mercury electrode without employing a ternary ‘eutectic salt mixture. The heat stability and versatile ’ solubility properties permitted a broad coverage of compounds investigated. I n addition to demonstrating the possible itppliration of fused salt polarography to the analysis of a variety of inorganic compounds, the results obtained indicate the relative ease of reduction under these conditions of the various c~onipoii(~tit metal ions studied. EXPERIMENTAL
N
OS=lQUSOCS polarography can be applied to advantage in the analysis of many organic substances that are insolullle in water. Polarography in nonaqueous solvents performed :it room temperature often results in decreased sensitivity due to the lower diffusion coefficients of the reducible species as well as greater difficulty in removing interfering dissolved oxygen. Both of these disadvantages can be minimized if the boiling point of the nonaqueous solvent permits t,he polarographic deterniination to be made a t higher than room temperature. Sachtrieb and Steinberg (9, 10) report the use of ternary salt mixtures acting as both solvent and supporting electrolyte in qualitative and quantitative analysis of inorganic compounds by application of dropping mercury polarography in the temperature range 125’ to 150” C. Lyalikov and Karmazin ( 7 ) report the use of solid microelectrodes in molten salt polarography at still higher temperatures. Apparently even under the latter conditions, concentration-dependent current-voltage curves are obtainable in certain cases. The present status of polarography in fused salt media has been reviewed by Lingane ( 6 ) . The main disadvantage of fused salt polarography is the tendency for reaction between the constituents of the system a t high temperatures. I n many cases the choice of salt and electrode system will help eliminate or control these side reactions, so that reproducible polarographic results can be obtained. Cnder these conditions, advantage can be taken of the excellent inorganicsolubility properties afforded by the use of molten salt media-for example, ordinarily insoluble oxides and carlionates are readily tlis.;olx-ed in many fused salt media. 1 Present address, Nuciear Engineering B- Manufacturing Department, North American Aviation. Inc., Dowmey, Calif. 1 Formerly a subsidiary of Standard Oil Co. of California, now incorporated into University of California Radiation Laboratory, Livermore. Caiif.
Polarography. Polarographic measurements were made at. 125’ =k 1’ C. with a Leeds & Sorthrup Electro-Cheniograph, Type E. Temperature cont,rol bvas maintained using Arocahlor (llonsanto Chemical Co.) fluid in a large stainless steel const,ant. temperature bath (Precision Scientific Co., Cat,alog S o . 10192). The solutions were deoxygenated by passing dry nitrogen gas through the molten ammonium formate for 10 minutes. -4 simple dropping mercury electrode assembly employing a mercury-pool anode-type cell (see Figure 1) with ground-glass connections was used. .ii capillary (E. H. Sargent Co., S-29351) \yas sealed into the end of the electrode assembly with Sauereisen S o . 1 paste, (Sauereisen Cements Co., Pittsburgh, Pa.), fol1onc.d tiy a coating of Fisher High-Pyseal (Eimer and Amend Cn.) to seal t,he pore space within the rigid Sauereisen union. C:ipill:ii,y characteristics and polarographic propert,ies employed at. 125’ i 1 C. were: m = 3.04 mg. per second, drop time = 2.7 sec.ond!: at h = 37.5 em., and m * ’ 3 f 1 ’ 6 = 2.10 mg.2’3 sec,-1’2 Under the conditions employed, the molten amnioniuni formate yielded a useful reduction voltage range of +0.1 to -0.9 is. a mercury pool. A similar voltage span of -0.1 to -1.1 1’s. a i l external anode containing mercury, the ternary salt mixture, sntl potassium chloride was observed by Sachtrieb arid Steiiibcrg (10).
Freshly opened sample bottles of C . P . anhydrous ammoitiuni formate (Baker & Adamson) were used in each polarographic, run. Check polarograms were made from time to time on the ammonium formate alone to ensure its continued purit,?. Passing nitrogen gas through the solutions a t t’he elevated tcniperature removed t,races of water. T o ensure anhydrous conditions during sample prep:ir:tt ion, t,he ammonium formate and the easily hydrolyzed materials such as uranium(II1) chloride, uranium(1T’) chloride, Zirconium chloride, thorium chloride, aluminum chloride, and the anhydrous rare earth salts were all weighed out and melted within a dry box. Polarography on the plutonium compounds was performed inside an alpha-hox.
ANALYTICAL CHEMISTRY
1560 Preparation of Compounds Studied. Cnless otherwise stated, the compounds used were Baker & Adamson C.P. chemicals. Uranium(V1) oxide was a purified grade from the Mallinckrodt Chemical Co. V202C1, (vanadyl chloride) was from Eimer & Amend. Uranium tetrachloride was a specially prepared and purified anhydrous grade, custom made by the A. D. MacKay Chemical Co. The hydrated salts, zirconium sulfate tetrahydrate, zirconium nitrate tetrahydrate, and zirconyl chloride octahydrate, were prepared in this laboratory from purified zirconium oxide by ordinary metathetical procedures. Their purity was substantiated by ignition analyses ( 1 ) . The purified zirconium oxide was obtained by ignition a t about 350" C. of the zirconium hydroxide precipitate formed from a solution of purified zirconyl chloride. Anhydrous zirconium chloride was made from the purified zirconium oxide and C.P. carbon tetrachloride by a method similar t o that described by Venable and Bell (15). Purity of the zirconium chloride sample was assured by gravimetric analysis after ignition a t 850' C. (per cent ZrOz: theoretical 52.9; found, 52.7). DETAIL DROPPING MERCURY ELECTRODE
CELL AND ASSEMBLY
i5 I I ~
TUNGSTEN
\%
/DROPPING MERCURY RODE ETAIL) SEAL
use three IO-gram portions of ammonium acetate axd evaporate the mixture t o about one half of its total volume in order to cause precipitation. Gravimetric ignition a t 850" C. (per cent USOS: theoretical, 60.4; found, 60.3 and 60.2) substantiated the formula as NH4U02(CzH302)3. Zirconium Mandelate (6). A 1.0-gram sample of zirconyl chloride octahydrate was dissolved in 20 ml. of 5 % hydrochloric acid. On addition of 165 ml. of 1 M mandelic acid, a white precipitate formed. The temperature of the solution was raised t o 85 O C. for 20 minutes, and the precipitate was filtered and washed with small portions of a hot solution containing 2 % hydrochloric acid and 5y0 mandelic acid. After drying over sulfuric acid in a vacuum desiccator, a sample was ignited to 850" C. (per cent ZrO?: theoretical 17.7; found 17.2). Thorium Succinate ( 3 ) . Approximately 25 grams of succinic acid was dissolved in 400 ml. of water. The pH was adjusted to 3.3 by adding 30% sodium hydroxide. About 2.5 grams of thorium nitrate (Baker & Adamson) was added and the mixture was heated t o 85' C. The white precipitate that formed was filtered, washed with ethyl alcohol, and dried over sulfuric acid in a vacuum desiccator. The ignition analysis a t 850" C. was (per cent ThOz: theoretical 56.9; found 56.2), based on the formulaTh[(CH2C00)2]2. Lanthanum Fluoride ( I d ) . Exactly 5.00 grams of lanthanum nitrate hexahydrate was dissolved in 50 ml. of water and then 15 ml. of 48y0 hydrofluoric acid was added. The precipitate was filtered and washed with 5% hydrofluoric acid and once with water. Polyethylene equipment was used. After thorough drying in a vacuum desiccator over sulfuric acid, the sample was weighed. The weight factor based on conversion of La(S03)3.6 H z 0 + LaFa.2H20is 53.6%. The weight conversion factor found was 53.8%; on this basis, material was designated as the dihydrate. The loss in weight on heating accurately weighed samples of the dihydrate a t 300" C. for about 2 hours under partial vacuum seemed to correspond to the formation of anhydrous lanthanum fluoride. Cerium Fluoride. Starting with ammonium ceric sulfate dihydrate from G. F. Smith Chemical Co., a procedure similar to that described above gave CeFr.zH20where x is 1 to 2. Dehydration as above gave a compound which mas considered as being anhydrous ceric fluoride. Polarographic reduction properties of the compound, deeignated as anhydrous ceric fluoride, indicated that material was different than the hydrate. Uranium Dioxide. Exactly 5.00 giams of uranium(\-I) oxide was heated at 330" C. for several hours while dry hydrogen gas was passed over the heated solid. A sand bath was used to maintain temperature control without overheating. The weight conversion factor, based on the reaction UO, HZ+ U 0 2 HzO, is 94.4%. The weight conversion factor found was 94.27,. The uranium(1V) oxide formed was dark brown. The original uranium(V1) oxide was yellow. This controlled temperature reduction resulted in an acid-soluble product which apparently was not refractory. Plutonium Compounds. A purified plutonium(1V) nitrate solution provided by Hanford Works, Richland, Wash., was standardized by a counting technique and then used in preparing all of the plutonium compounds investigated polarographically. Accurately known quantities of plutonium(1V) oxide were obtained by evaporating aliquot portions of the standard plutonium(1V) nitrate solution to dryness and then heating a t 350" to 400' C. for about 6 hours. The plutonium(V1) used in preparing the plutonyl salt was obtained by oxidizing plutonium(1V) in 0.5-TI nitric acid by heating t o approximately 90" C. for IO hours ( I S ) . Solid sodium plutony1 acetate, XaPuOt( C~H302)3, was precipitated from the plutonium(V1) solution by buffering R ith sodium acetate and acetic acid by a procedure similar to that described for sodium uranyl acetate. Purity of the salt was assured by counting technique-i.e., activity relative to original plutonium(1V) used in preparation.
+
PLATINUM WIR
(E H SARGENTCO
Figure 1. H i g h temperature polarographic
apparatus Anhydrous lanthanum chloride, ytterbium chloride, and thorium chloride and the anhydrous rare earth chlorides, praseodymium, neodymium, gadolinium, and samarium, were prepared by dehydrating the corresponding hydrated salts in a stream of anhydrous hydrogen chloride a t about 250" C. ( I S ) . These hydrated salts were the best grades available from Research Chemicals, Inc., Burbank, Calif. Purity in each case was reported to be a t least 99.8%. Anhydrous uranium(II1) chloride was prepared from uranium metal (Mallinckrodt) via conversion t o uranium hydride and hydrochlorination, as described by Spedding and others (11, 14). The uranium(II1) chloride was analyzed for uranium gravimetrically bv ignition of a small sample, covered with oxalic acid, a t 850" C., forming u308. Theory for uc13: 81.5% u308; found 81.8. Sodium Uranyl Acetate. 0.5M uranyl nitrate (33 ml.), 4 M sodium nitrate (33 ml.)) and O.1M nitric acid (33 ml.) were combined and the mixture was heated t o 70" t o 80' C. Six milliliters of glacial acetic acid was added. Upon the addition of 10 grams of sodium acetate, a precipitate was obtained. The precipitate was digested for a few minutes a t 75" C. and then filtered, washed with small portions of ethyl alcohol, and dried in a vacuum desiccator over sulfuric acid. Ammonium Uranyl Acetate. This salt was prepared by essentially the same method as the sodium uranyl acetate, except that ammonium nitrate and ammonium acetate were used instead of the corresponding sodium salts. It was found necessary to
+
RESULTS AND DISCUSSION
The polarographic results obtained on the various compounds investigated are given in Table I. The more reduction-resistant compounds-e.g., barium, magnesium, and zirconium-did not form half waves, presumably because of preferential or simultaneous reduction of the ammonium formate solvent. I n these cases, decomposition potentials of these compounds in ammonium formate were evaluated and tabulated for comparison with the ammonium formate alone. Decomposition potentials in the range -0.55 to -0.65 volt, obtained with the annydrous barium
V O L U M E 27, NO. 10, O C T O B E R 1 9 5 5
1561
and 'magnesium compounds, possibly indicate that these cations me reduced, but simultaneous reduction of some ammonium formate solvent also occurs, thereby preventing the formation of clearly defined half waves. That hydration of a salt increases the reduction resistance is seen by noting that anhydrous lanthanum fluoride yields a Elit value while lanthanum fluoride di-
Table I.
Half-Wave and Decomposition Potentials of
0.001M Solutions of Various Compounds in Molten Ammonium Formate at 125" C. Compound Ammonium formate alone AgCl AuC1a' HC1.3H?O AlCla Al(0H)s NaA10z AszOs NaAsOz BaFz Bas04 B1Ch BiOCl BizOa CaFz CdClz CdCOa CdO COCO3 Cos04 C0203 CrCla.6HzO CrFi
-Ei/z
Id/c,
p n. mS
-Ed.o.
0 90 (r
0.82 0.83
19 20
I 0.31 I1 0.60 I 0.60 I1 0 . 7 1
I1 14 I 14
I
7
I1
7
a
0.90
0.55 0.65
a 0
0.76 0.17 0.19 0.26 0.55 0.56 0.70 0.27
I 0.25 I1 0 . 5 6
0.17 0.17
("4)2>f004 NiCOs PbO PbSOi SbCls SbzOa NazSiFs SnO SnOz SrFz SrSO4 ThCla Th[(CHzCOO)zl? Thorium succinate Th(NOs)r,4H>O TiOz (V102Cld Vanadyl chloride NHiVOs Ijawo4.2H20 ZnCOs ZrOClr '8HzO Zr(NOs),.4Hz0 Zr(SO4)z'4Hz0 ZrClr Zr(CsHa-CHOH-COO)r Zirconium mandelate
10 8.2 8.3 10 10.5 11 4.0 5.1
I 5.0 I1 9 . 7
P
0.68 0.70
17 14
0.05 0.45 0.12 0.21 0.05c 0.04c
17 10 9.8 10 10
I 9.2 I1 1 0 . 3
0.76 0.75
5.0 5.5
I1 0.76 0.61
0.70
Pb++
9
I I1
5.0 4.8 7
7
E a r e Earths and Related Compounds CeFa, z Hz0 (NHdrCe(S01t4 ?H?O 0.85 5.5 CeF4 0.40 5.3 GdC18 0.78 16 LaCla LaFs 2H20 LaF3 0.75 16 La(NOd3 6HzO 0.85 I5 NdCIa 0.84 16 PrCla 0.76e 11 SmCla 0.30 YbCla 5.0
+ 2e
-L
Pb" and C d + +
+ 2e
-L
Cd"
0.55 0.90
I
Plots of log __ us. E usually were nonlinear and slope analysis I d
0.60 0.60 0.60 0.65 0.70 1.d.w. b 0.55 0.90e
4.5
0.08 I 0.31 I1 0 . 7 2
I 0.48
0.55 0.55
hydrate does not. Further evidence in regard to the influence of hydration is found by comparing the polarographic results obtained from anhydrous chromium( 111)fluoride with those from chromium(II1) chloride hexahydrate and anhydrous thorium chloride and results from thorium succinate with those from thprium nitrate tetrahydrate. Apparently neither hydrated nor anhydrous zirconium salts yield half-wave potentials. That the decomposition potentials ( E d . p . ) of the hydrated zirconium salts are less than those for the anhydrous zirconium salts is probably due to the reduction of water and its influence on the Ed.p.values. All ammonium formate solutions investigated polarographically were completely clear, indicating complete solubility. A comparison of the polarographic results obtained with such compounds as cadmium chloride, cadmium carbonate, and cadmium oxide seems to indicate that counter ions within a compound exert little influence on half-wave potentials (E1/*)as long as complexation does not occur. Apparently the situation is analogous to aqueous polarography in this respect. Without knowing diffusion coefficients of the various ionic species investigated, it is not possible to apply the Ilkovi6 equation ( 4 ) and thereby evaluate precisely the number of electrons involved in the various reductions. Plausible or "possible electrode reactions" are indicated below for various reductions. The number of electrons postulated in these cases is based on halfrrave height comparison-Le., Zd/C values-between the reducible species and ionic species of known reductions-e.g.,
0.90
0.65 0.90
0.55 0.65
0.45 0.60 0.60 0.58 0.82 0.83
O.RO 0.60 0.90 0.90 0.60 0.82 0.60 0.65 0.70 0.60 0.90
-1
values were considerably greater than those corresponding to reversible reductions. Hydrated hexavalent uranium salts-e.g., uranyl nitrate hexahydrate and uranyl chloride dihydrate-showed well-defined reduction waves, thereby permitting evaluations of halfwave potential. A given concentration of uranium salt yields different half-wave potentials and varying diffusion currents (wave heights) depending upon the length of time the system is maintained a t 125' C. For this reason these El,* values are not reported. I n all cases, these half-wave potential values were between -0.10 and -0.50 volt. Probably the uranyl ion is reduced slowly by molten ammonium formate. The mercury normally present during the polarographic runs apparently promotes the reaction, as evidenced by the deep yellow solution formed only when mercury is present during the aging of the melt. Data obtained on anhydrous uranium compounds under various aging conditions (Table 11)show the influence of reaction between uranium(V1) and molten ammonium formate. When hexavalent uranium compounds were aged for a minimum period -i e., only long enough to deoxygenate the solutions, approximately 5 minutes-half-a ave potentials were not obtained. Only after the aging period allowed reduction of the uranium(T'1) to some lower valence state, probably quadrivalent, was polarographic reduction evident. Quadrivalent uranium compounds, uranium(II1) oxide and uranium(1V) chloride, a t lo^ concentrations-e.g., 0.001M-were reduced very slowly by the ammonium formate and then well defined polarographic properties were obtained (see Table 11). Using the comparative wave height method discussed above, the two reduction n-aves observed for uranium(1V) oxide and the three waves found for uranium (IV) chloride can be explained as follows:
g7
I d / C . Final units( = microamperes per millinorrnality) ,1111). I a Formed hlack ppt. on dissolving in ammonium formate, presumably due t o reduction to metal. b 1.d.w. Large decomposition wave initially. C Potential after 1 hour in mercury pool cell. E v z . Half-wave potential u s . mercury pool. Ed.i). Decomposition potential us. mercury pool.
and
-
u++++e
e
2e
U+'+ +u + ++U "
ANALYTICAL CHEMISTRY
1562 These results are in agreement with Driggs and Lilliendahl's observations ( 2 ) that hexavalent uranium compounds (uranyl radical) do not electrolyze to uranium metal, while quadrivalent uranium compounds such as UCla and KUF6 yield metallic uranium on ordinbry electrolysis in fused salt media. It should not be inferred, however, that the polarographic results obtained actually prove the existence of specific intermediate valence states for uranium or the formation of uranium metal under the conditions prevailing in the system investigated here. The plutonium analogs of the above uranium compounds were also investigated polarographically (Table 11). I n this case, plutonium(VI), plutonyl ion, showed no half-wave potential, nor any tendency to be reduced by the molten ammonium formate-mercury Rysteni. Plutonium(1V) as either the oxide or
the hydrated nitrate showed a single reduction wave. The extremely small solubility of pliitonium( 111) oxide prevented a wave height analysis. The I d / C values for quadrivalent plutonium nitrate reduction seem to indicate the following rcnction;
PU+'+T
Table I l l . Salt CdCh
CdCO3
e
pu+++
Concentration Study on Cadmium Salts .lf 0.001 0 ,005 0 010 0 001 0.006
0.010
-El/ z 0.17 0.23 0.26 0.19 0.25 0.29
I d / C , '8mS 8.2 8.2 8.0 8.3 8.0 8.4
Table 11. Polarographic Data on Uranium and Plutonium Compounds in Molten Ammonium Formate at
125" c.
Compound L.01
UOd
31'
Aging Tinie in Cell, Hr.
0.001
0.001b
0.5 1.5 2.5 4.5 6.0 a
6.0
7.0 0.001 1 0
2 0 3.0 0.001
UCl< UCI4 UClr UClS NaPuOz(OAc)1
0 0 0 0 0
SaPuOn(0Ac)a
0.001 e
0 : 1.0 O02.jp
0050e 0100' 011 001
Pu(NOs),. S H z 0 0 . 0 0 1
1 0
2 0
PUOl
0.001~
, . .
0.'1'2 0 . 8 3 0.32 , . . 0.37 . . . 0.37 . . . 0.38 ...
0.5 1.5 3.0 4.0
VCl,
...
0.5 2.0 3.0 4 .0 0.5 2.0 3.0 4.0
i n
2 0
I11
... ...
0.5 1.0 2.0 3.5
a
KO2
I1 ... ...
0.11 0.75 0.16 0.80 021 ... 0.24 . .. 0.27 . . .
3 .0
Id/c,
-Ell2
I ,.. 0.10 0.15 0.19 0.22 0.25
...
I
...
4 0 8.0 10.0 102 10.3
0.37
...
. .
,..
...
...
4.5 6.0
,..
0 12 0 15 n 17 0 19
0 80 0 82 o 83 0 85
... ... . ..
0 73 0 . 9 4 0.10 0.74 0.95 0.11 0.74 0.95 0 10
6
4.0 4.0 4.0 4.1
0 47
0.5
0 48
0.5
n 47
...
ACliNOWLEDG.MENT
, . .
Thanks are due J . &I. Scarborough and B. J. Corts of this laboratory for preparing some of the compounds used in this investigation. T. J. Biel's help in recording many of the polarograms is greatly appreciated. Work was performed under Contract S o . -4T(lI-l)-i4 with the U. s. Atomic Energy Commission.
,
.
REFEREKCES
Colichman, E. I,.. and Ludewig!, W.H . , A 4 ~ CH . ~ ~ .
3.9 4.0 4.0 3.9
5.0 5.3 11 5 . 2 5 . 0 12: 5.1 5.2 Ild
4.1 4.2 4.2
.,
The results in Tables I and I1 indicate the relative ease of reduction of the various ionic species investigated under the conditions prevailing in this investigation-namely, in molten ammonium formate containing mercury at 125' C. That the polarographic system described here can be applied to quantitative analysis is seen by a consideration of results given in Table 111. A given ionic species must be stable in the molten ammonium formate system if quantitative results are to be obtained. The excellent solubility properties exhibited by molten ammonium formate for both water-soluble and water-insoluble compounds make it a desirahle system for the polarographic det rrniination of a large variety of compounds.
, . .
... 7.5 . . . 10.0 , . . 10.1 . . .
... ,
... ...
... 9.A .. 10.2 .. 10.5 . . . 10.0 , . .
4.8 4.7 5.0 16
,..
i:o
7
0 . 1 2 n.r. ... 0 . 1 1 n.r. , . . 0 . 1 3 n.r. ... 0.76 . . . , . . No wave8 - Ed.0. = 0.90 No waves -Ed... = 0.90 0.45 046 0 4.5
I11
7.0 7.0 7.0 3.3 7.2 0 7.2 0 7.3 0
,.. ... ,..
0.14 0.20 0.27 0.35 0.36
I1
0 2 5 6 6.6 7.0
0.18 0.22 0.32 0.36 0.38
...
LB-
_ _ _ m_ ~
. . . . .
. . . . ... ...
0.5
Run as raliidly as pobsible in cell after niiniinuiii deoxyaenating period. 2, Preaged before polarographic run for 3 hours a t 125' C., no mercury present. c Preaged before polarographic run for 6 hours a t 126' C.. mercury present. d Diffusion current corrected for siiiall solvent decomposition current a t these voltages. e Blackening o n adding solrition to mercury pool cell indicates some reduction of UClr iininediately a t the higher concns. f Concns. higher than 0.001 wm. (weight molar) formed black deposit too rapidly and could not be run polarographically. Y Only a small quantity of Pu01 dissolved even after 1 h o u r a t 125' C.; thus s o h . is Ratd.. not 0.001 wm. n.r. Not reliable, reduction wave I1 merges with solvent-supporting electrolyte decomposition wave giving ( E V ~ I I0.9 volt.
(1953). Driggs, F. H., a n d Lillieiidahl, \V. C., I n d . Eng. Chem., 22, 516 (1930). G o r d o n , L., T-anselow, C. H . , a n d Willard, H . €I., Ihid., 21, 1323 (1929). Kolthoff, I. AI., a n d L i n g a n e , J. J., "Polarography," 2nd ed.. vol. I, p. 63, Interscience, S e w York, 1952. K u m i n s , C. .I.. .XS.IL, CHEM.,19, 376 (1947). Lingane. J. J.. Ihid.. 23, 96 (1951). L y a l i k o v . Yu S.. and K a r i n a z i n , T'. I., Zarodskaljn Lah., 14, 138, 144 (1948). LlacKenzie. D . 11.. .\toink E n e r g y Commission, D o c u m e n t CRC-487 (Decewher 1951). K a c h t r i e b , S . H., atid Steinberg, SI., J . A m . Chert?. S o c . , 70, 2613 (1948). Ihid., 72,3558 (1950). S e w t o n , .I.S.. W a r f , J. C . , Spedding, F. H . , a n d others. S u c l e onics, 4 , No. 2. 17 (1949). R o d d e n , C. J.. Editor, S a t j o n a l Nuclear Series. Division V I I I , ".lnalytical C h e m i s t r y of the M a n h a t t a n Project." p. 497, McGraw-Hill. S e w York, 1950. S p e d d i n g , F. H.. and Lliller, C. F., .Itomic E n e r g y Commission, D o c u m e n t ISC-167, 21 ( J u l y 1951). S p e d d i n g , F. H., S e w t o n . -4.S., W a r f , J . C.. a n d others, .Vudeo n i c s , 4 , S o . 1,4 (1949). T e n a b l e , F. P.. a n d Bell. J. AI., J . Am. Chem. Soc.. 39, 1598 (1917); 4 6 , 1834 (1924). RECEIVED for review lIarc11 3. 1955.
Accepted July 21. 195.5.
