NOTES
250
The values of the heat of fusion (AHf), the entropy of fusion (AHfITf), and the cryoscopic constant (RTo2Ml/AHf1000) for the lithium chloridepotassium chloride eutectic mixture obtained in the present work, 3.20 A 0.06 kcal. mole-', 5.1 i 0.1 kcal. mole-l deg.-', and 13.7 h 0.03 deg. mole-' kg., respectively, are recommended for use in quantitative calculations of thermodynamic properties in this melt as solvent. Acknowledgment.-The authors wish to thank J. B. Milgram of Foote Mineral Co. for drawing the work of Powers and Blalock to their attention during the course of the present investigation.
Vol. 62 2.4
4
g 2.0
.3
Y
% 'El B n
g 1.6
w
SOME CATION-EXCHANGE EQUILIBRIA , ON DOWEX 50 AT 85'' BY 0. D. BONNER,C. F. JUMPER^
AND
0. C. ROQERS~
Department o f Chemistry, University of South Carolina, Columbia, South Carolina Received September 6 , io67
Summaries of the results of ion-exchange equilibria and of maximum water uptakes at 25" of Dowex 50 resins of 4, 8 and 16% DVB content involving the common univalent3 and divalent4 ions have been reported previously. Exchange data for one additional univalent ion, hydroxylammonium ion and two divalent ions, manganous and beryllium ion are included in this report. The investigations of ion-exchange equilibria have also been expanded to include exchanges involving the three trivalent ions: chromic, cerous and lanthanum ion.
1.2
I
I
I
I
I
1
40 60 80 100 Mole yo hydroxylammonium resin. Fig. 1 .-Hydroxylammonium-hydrogen exchange: A, 16% DVB; B, 8% DVB; C, 4% DVB. 0
20
Experimental The batch method of equilibration of resin and aqueous phases and the general method of separation and preparation for analysis of these phases have been described in detail.6 The analytical procedures, of course, vary with the ions involved in the exchange. Hydroxylammonium-Hydrogen Exchange.-Hydroxylammonium ahd hydrogen ion were determined by titration with standard sodium hydroxide. Two distinct breaks appear in the titration curve, at pH values of about 4.2and 9.0. The first break corresponds to the neutralization of hydrogen ion and the second break to the total of hydrogen 0 20 40 60 80 100 and hydroxylammonium ion. Mole % ' calcium resin. Calcium-Nickel Exchange.-The total concentration of both ions was determined by compleximetric titration with Fig. 2.-Calcium-nickel exchange: A, 16% DVB; B, 8% DVB; C, 4% DVB. a standard solution of the disodium salt of ethylenediaminetetraacetic acid in ammoniacal solution, l-(Z-pyridyl-azo)2-naphthol, PAN, serving as an indicator. Nickel ion con- were determined by precipitation as the sulfate. Beryllium centrations were determined by the same titration except ion concentrations were determined by potentiometric titrathat the pH was maintained a t about 5.8 by a sodium ace- tion with standard sodium hydroxide solution. A distinct tate-acetic acid buffer. Calcium ion concentrations were break occurs in the titration curve which corresponds to the total hydrolysis of the beryllium ion. then calculated by difference. Cerous-Silver Exchange.-Silver ion was determined by Manganous-Nickel Exchange .-Nickel ion was determined by compleximetric titration in acidic media at O", potentiometric titration with standard sodium chloride pyrocat&hol sulfonphthalein serving as an indicator. solution. Cerous ion was oxidized to ceric with ammonium Manganous ion was also determined by compleximetric ti- persulfate and then titrated with standard arsenite solut.ion, tration in ammoniacal medium with standard disodium Ferroin serving as an indicator. EDTA, sodium 1-(l-hydroxy-2-naphthylazo)-6-nitro-2- Lanthanum-Cerous Exchange.-The total concentration napthol-4-sulfonate, Eriochrome black T, serving as an in- of cerous and lantlianum ion was determined by complexidicator. This titration was carried out in the presence of metric titration with a standard solution of the disodium salt of EDTA at a pH of 5 . 5 , PAN serving as the indicator. KCN to mask the nickel ion, and of ascorbic acid. Barium-Beryllium Exchange .-Barium ion concentrations Cerous ion concentrations were determined by the method described above and lanthanum ion concentrat,ions were then (1) These results were developed under a project sponsored by the calculated by difference. United States At,omia Energy Commission. Cerous-Chromic Exchange .-Total cerous and chromic (2) Part of the work described herein waa included in theses subion were determined by the persulfate oxidation method mitted b y C. F. Jumper and 0. C. Rogers to the University of South described above. Chromic ion concentrations were deterCarolina in partial fulfillment of the requirements for the degree of mined by the method of Banks and O'Laughlin,B a selective Master of Soience. oxidation of the chromic ion with perchloric acid. After (3) 0.D. Bonner, THIS JOURNAL, 69,719 (1955). (4) 0.D. Bonner and L. L. Smith, ibid., 61,326 (1957). (5) 0.D. Bonner a n d V. Rhett, ibid., 67, 254 (1953).
(6) C. V. Banks and J. W. O'Laughlin, Anal. Chcm., 28, 1888 (1956).
NOTES
Feb., 1958 the direct determination of chromic ion, the cerous ion concentration was calculated by difference.
Discussion and Results The ion-exchange process may be represented by the equation
+
~ ( A ' + ) o dB"+)i = p(A")i
+ p(BP+)o
(1)
where A and B are the exchangeable ions of valence q+ and p + , respectively, and o and i represent the aqueous and resin phases. The equilibrium quotient may then be defined as
1.25
4
log k' d X
(3)
where K' is the equilibrium quotient corrected for solution phase activity coefficients and X is the equivalent fraction of the preferred ion in the resin phase. Univalent Ions.-The affinity of the hydroxylammonium ion for ion-exchange resins relative t o that of other ions should be of interest because of its many uses and because of the similarity between its structure and that of the ammonium ion. The equilibrium quotient.-resin composition curves show that it has an average affinity for sulfonate resins almost identical with that of the ammonium ion.9 The shapes of the curves for the ammonium-hydrogen and hydroxylammonium-hydrogen exchanges are, however, quite different. The ammonium-hydrogen exchange curves resemble closely the alkali metalihydrogen exchange curves while the slope of the hydroxylammonium-hydrogen curve is opposite in sign to that of these curves over much of the range of resin composition. Activity coefficient data for aqueous solutions of hydroxylammonium chloride are unavailable and so this cation cannot be placed in the quantitative selectivity scale. Values of the equilibrium constant, K , uncorrected for solution phase activity coefficients, of 1.44, 1.77
I
x
B 1.20 -
.+ 42
g1.15
g 1.10
V
I\
"'
.3
3
1.05
3
51.00
0.95
0
20 10 60 80 100 Mole % manganous resin. Fig. 3.-Manganous-nickel exchange: A, 16% DVB; B, 8% DVB; C, 4% DVB.
where N is the mole fraction of the ion in the resin phase and m is the molarity in the aqueous phase. This equilibrium quotient, k , varies with resin composition, N , because of the neglect of activity coefficients in both phases. The equilibrium constant, R,is calculated7,*from the equation log K =
25 1
7.0
2 5.0 al
.e 42
s
0
$
'E
B n 1
w" 3.0
1 .o 40 60 80 3.00 Mole % . _barium resin. Fig. 4.-Barium-beryllium exchange: A, 16% DVB; B, 8% DVB; C, 4% DVB. 0
20
and 2.23 for the hydroxylammonium-hydrogen exchanges on 4, 8 and 16% DVB resins, respectively, would place this ion between sodium and ammonium3ion in the selectivity scale (Table I). Divalent Ions.-The calcium-nickel exchange was ipvestigated as a check on the accuracy of the nickel-cupric exchange which has been previously T.4BLE 1 reported.4 For the 4 and 8% DVB resins nickel APPROXIMATEPOSITIONS OF IONS I N THE SELECTIVITY was shown to have a greater affinity for the resin SCALE RELATIVE TO LITHIUM IONTAKEN AT 1.00" than cupric ion. On the 16% DVB resins, how4% 8% DVB DVB ever, the relative affinities were reversed. Upon obtaining the calcium-nickel exchange data, a NH30H + 1.90 2.25 3.28 triangular comparison was made by making use of Mn +2 3.42 4.09 4.91 of the calcium-cupric data already available. l o AlBe+2 3.43 3.09 6.23 though chlorides were used for the calcium-cupric 6.6 7.6 10.5 Cr +3 7.5b 10.6b 17. O b Ce +a exchange and nitrates for the other exchanges the La fa 7.6 10.7 17.0 triangular comparisons shown in Table I1 are quite These values are uncorrected for solution phase activity satisfactory and verify the previous data. coefficients. Average values computed from results of the Equilibrium constants calculated for the manBa-Ce and Ce-Ag exchanges. ganous-nickel exchanges on 4 , 8 and 16% DVB res(7) W. J. Argersinger, A. W. Davidson and 0. D. Bonner, Trans. ins are 0.99, 1.04 and 1.21, respectively. Although Kana. Acad. Sci., 63, 404 (1950). the lack of activity coefficient data prevents the (8) E. Hogfeldt, E. Ekedahl and T.G. SillBn, Acta Chenz. Scand., 4, placement of manganous ion exactly in the selec828 (19501. (Q) 0.D. Bonner, THISJOURNAL,68, 318 (1954).
(10) 0.D. Bonner and F. I,. Livingston, ibid., 80, 880 (1968).
NOTES
252
0
40 60 80 100 Mole % cerous resin. Fig. 5.-Cerous-silver exchange: A, 16% DVB; B, 8 % DVB; C, 4% DVB. 20
Vol. 62
20 40 60 80 100 Mole % lanthanum resin. Fig. 7.-Lanthanum-cerous exchange: A, 16% DVB; B, 8% DVB; C, 4% DVB. 0
1.4
2.0
1.3
1.8
1.2
1.6
.)
.G
.B
4
8 1.4 w
E,
.-E,
'E:
& 1.0 .e
3 s 1.2
w"
r4
s
0.9
1.0
0.8
0.8
0.7
0.6
40 60 80 100 Mole yo barium resin. Fig. 6.-Barium-ceroua exchange: A, 16% DVB; B, 8% DVB; C, 4% DVB.
'20 40 60 80 100 Mole % ceroua resin. Fig. 8.-Cerous-chromic exchange: A, 16% DVB; B, 8% DVB; C, 4% DVB.
tivity ~. scale it appears to fall between nickel and calcium ion. Equilibrium constants calculated for the bar-
ium-beryllium exchanges, ignoring solution phase activity coefficients, are 2.18, 2.88 and 3.34 for exchanges on the 4, 8 and 16% DVB resins, respec-
0
20
0
,I
