July 5 , 1959
CERIC REDUCTION AND RADIOLYTIC HYDROGEN YIELD
were observed in the polyphosphate complexes of sodium and potassium. The larger effect in the acidic pyrophosphate complex of calcium probably is due to the Closer aPproach of the hydrogen ion in the PYroPhosPhate complex in contrast to its approach in the triphosphate complex. This effect should be greater in the case of calcium which is already less firmly bound than magnesium.
[CONTRIBUTION FROM
THE
3203
Acknowledgment.-The authors wish to acknowledge the financial assistance of a Post Doctoral Fellowship granted t o s. M. L. by the Ohio State University Advisory Committee on Grants-inAid. COLUMBUS, OHIO
CHEMISTRY DIVISION,OAK RIDGENATIONAL LABORATORY]
Ceric Reduction and the Radiolytic Hydrogen Yield' BY H. A. MAHLMAN RECEIVED DECEMBER24,1958 The hyrlrngen yields observed in the cobalt-60 y-rag irradiation of sulfuric acid solutions of ceric ions indicate a n acid indcpendeiice to 0.8 M H ~ S O I . T h e suppressive action of the solute may be expressed by the equation G(H2) = -0.21 [Ce'Y]l'a 0.44. T h e scavenging effect of ceric ion indicates t h a t the theoretical cerous yield may be obtained only in infinitely dilute ceric solutions.
+
ceric ion concentration on the hydrogen yield and may be expressed by the least squares determined 0.44. The equation G(H2) = -0.21 [Ce1"j'/8 concordance of the data indicates that the hydrogen yields in 0.4 and 0.8 A f H2SOa solutions containing CeIV ions are the same. The hydrogen yields reported for oxygenated 0.4 M H2S04 solutions containing 0.01 and 4 X loe4 M ceric ion? are in agreement with these experimentally determined values when corrections are made for the suppressive effect of oxygen. Recalling the mechanism of ceric reduction in 0.4 M H2S04 solution8 and that ions reducible by H atoms lower the hydrogen yield one may see readily that a decrease in the hydrogen yield will cause an equivalent increase in the cerous yield. Appropriate calculations for 400 and 1000 micromolar ceric solutions 0.4 M H2S04 show that the G(CelI1) should be 2.37 furic acid and G. Frederick Smith analytical reagent ceric and 2.38, respectively. These calculated values acid sulfate. Water from a Barnstead still was purified for the Ce"' formation in 400 and 1000 micromolar and stored in silica vessels. All irradiations were made in a 900 curie cobalt-60 y-ray source. The dose rate was de- ceric solutions are in agreement with the values ~ G(CelI1) = 2.37 termined by the Fricke dosimeter assuming t h a t 15.60 fer- G(Cel") = 2.39 ( S w o r ~ k i )and rous ions were oxidized per 100 e.v. of absorbed energy.5 (Masters and Challenger) .lo Since the extrapoT h e additional energy absorption due t o the added solute lated hydrogen yield a t zero solute concentration is was calculated.6 The yield, G(product), defined as the 0.01 one may conclude that the G(H,) is the number of ions formed per 100 e.v. of absorbed energy, was 0.44 same and equal in 5 X to 0.8 M H2S04solucalculated from the total absorbed energy. Analytical
The hydrogen yields in cobalt-60 y-ray irradiation of 0.4 M H2S04solution and dilute H2S04 solution pH 2 have been generally accepted to be 0.40 and 0.43, respectively.2 I n disagreement i t was reported that in 0.4 M HzS04 and 0.5 X lod3to 0.5 X M H2S04 solution^,^ containing loe3 M KBr to protect the molecular hydrogen formed from radical attack, the hydrogen yield was the same and equal to 0.45. The presence of HSO4- and SO4' has been shown to have no effect on the hydrogen yield from cobalt-60 irradiated solution^.^ The purpose of this paper is to present confirmatory evidence that the G(H2) in a 0.4 M HzS04 solution is 0.45, that this yield is constant to 0.8 M HzS04 and to show that the G(CelIT) in an 0.4 M H2S04-CeTv solution can approach 2.34 only when the concentration of CeTVapproaches zero. The chemicals were Baker and Adamson C.P.grade sul-
+
*
measurements of ferric ion concentrations were made directly on a Cary Recording Spectrophotometer at 3050 it. using a molar extinction coefficient of 2240 a t 25.'5 Determination of the S.T.P. volume of the molecular hydrogen formed was made by ignition with oxygen on a platinum filament. The volume of solutions irradiated was determined by weight after the irradiation and hydrogen analysis.
TABLE I HYDROGEN YIELDS OBSERVEDIN CerV-H2S0, SOLUTION
The hydrogen yields were determined a t two closes, O.G X IOzoe.v. and 1.2 X lozoe.v. in solutions 0.001, 0.003, 0.008, 0.026, 0.064 and 0.10 molar CeTVand two acidities 0.4 and 0.8 M H2S04. The data in Table I illustrate the suppressive effect of (1) Work performed for t h e U. S. Atomic Energy Commission a t the Oak Ridge National Laboratory, Oak Ridge, Tennessee, operated by Union Carbide Corporation. (2) C. J. Hochanadel and S. C. Lind, A n n . Rev. P h y s . Chem., 7, 83 (1956). (3) H. A. Mahlman and J. W. Boyle, THISJOURNAL. 8 0 , 773 (1958). (.1) H. A . hlahlman, J . Chem. P h y s . , 28, 1256 (1958). (5) C. 1. Hochanadel and J. A. Ghormley, ibid.. 21, 880 (1053). (6) H . A. Mahlman and G. K . Schweitzer. J. I n o r g . N a c . Chem., 6, 213 (1958)
Initial Ce'"
0 4 hf HE04
0.8 If HaSO,
None 0,001
0.45" .41b . 40b
0.44"
.003
. 40
,008 .02F
.38h
,064
.IO
" Contained
M
.41* .40* .40
.
.34 .35 .34 .34 KHr. * Single determinations.
(7) J. A. Ghormley and C . J . Hochanadel, Rodiofion Researrh, 3, 227 (1955). (8) A. 0. Allen, ibid., 1, 85 (1054). (9) T. J. Sworski, ibid., 4,483 (1956). (10) B. J. Masters and G. E. Cbailenger, J . P h y s . Chem., 5 9 , 1093 (1955).
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KURTA. KRAUS,DONNA C. MICHELSON AND FREDERICK NELSON
tions. The dependence of G(H2) on a function of the ceric concentration indicates that the presently accepted theoretical yield of cerous ion [G(Ce"') = 2.341 may be obtained only in an infinitely dilute ceric solution.
[CONTRIBUTION FROM
THE OAK
VOl. 81
Acknowledgment.-The author gratefully acknowledges the help of the discussions with C. J . Hochanadel, j. jv. Boyle and p. S, Rudolph. OAKRIDGE,TESN.
RIDGEx A T I O N A L LABORATORY CHEMISTRY DIVISION]
Adsorption of Negatively Charged Complexes by Cation Exchangers1 BY
KURT
A.
KR.kUS,
DOKNAc. MICHELSON
AKD
FREDERICK NELSON
RECEIVED DECEMBER 10, 1955 Stroiig adsorption of some iiegatively chargcd complexes by cation-exchange resins is demoiistrated. This adsorbability, which is negligible a t low ionic strength, increases rapidly with ionic strength, is much greater from salt than from acid solutions and is strongly dependent on t h e type of the metal complex. LVith concentrated chloride salt solutions, distribution coefficients larger t h a n lo6 were found for trace amounts of t h e anionic complexes (MC14-) of Fe(III), Ga(II1) and Au(II1). Under these conditions adsorbability of the anionic complexes of Sb(V) and Tl(II1) is considerably less and t h a t of the complexes of M n ( I I ) , Co(II), Zn(II), Bi(II1) and Sn(1V) is essentially negligible. Use of the adsorption of anionic complexes for separations by cation exchangers is illustrated with several examples.
One usually assumes in the ion-exchange field that cation exchangers adsorb only positively charged ions and anion exchangers only negatively charged ions. These restrictions are tempered by the recognition that, particularly a t high ionic strength, substantial electrolyte invasion of the resin may occur and that uncharged species ( e . g . , organic molecules, bromine, iodine) may be adsorbed; strong adsorption of anions by cation exchangers (or cations by anion exchangers) seems not to have been seriously considered. Since adsorbability of some negatively charged complexes by anion exchangers is extremely high,2 the question arose whether part of this high selectivity of the anion exchangers results from interactions of the complexes with the organic network. One might then expect that a t least those negatively charged complexes which are very strongly adsorbed by anion exchangers could :tlso be adsorbed by cation-exchange resins. This prediction was verified in a series of adsorption studies with the strongly acidic exchanger Dowex-50. This resin was chosen since it has the same organic network (polystyrene-divinylbenzene) as the Dowex-1 resin used for the earlier anion-exchange studies. Characteristic features of anion-exchange adsorption of many metal complexes are a rapid rise of adsorbability with increasing salt concentration and a rapid divergence of adsorbabilities between those found in acids and their corresponding salt^.^,^ In the search for adsorption of anions by (1) T h i s paper is based on work done f o r t h e U. S. Atomic Energy Commission a t t h e Oak Ridge National Laboratory, Oak Ridge, Tennessee, operated by Union Carbide Corporation. It is based on work summarized in t h e Chemistry Division Semiannual Progress Kegort, OKNI, ZO-lIj, July t o December 1955. (2) See e . g . . K. A. Kraus and F. Nelson, "Anion Bxchauge Studies of t h e Fission Products," Vol. VII, Proceedings of t h e International Conference on t h e Peaceful Uses of Atomic Energy, Geneva, 1955, United LTations, New Bork, N. Y., 1956, pp. 113, 131. ( 3 ) (a) K. A. Kraus, F. Nelson. F . B. Clough and K. C. Carlston. T H I S J O U R N A L . 7 7 , 1391 (1955); (b) K . A. Kraus, "Ion Exchange," in "Trace Analysis," Symposium a t t h e New X'ork Acn
