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Kinetics of ion exchange of some metal ammines in hydrous zirconium(IV) oxide
J inorg nucl Chem Vol. 41. pp. 1183-I 18~ ~ Pergamon Press Ltd. 1979 Printed in Great Britain
0022-1902/79/0801-11831502.0010
KINETICS OF ION EXCHANGE OF SOME METAL AMMINES IN HYDROUS ZIRCONIUM(IV) OXIDE R. K. SRIVASTAVA and B. PAL Department of Chemistry, D.B.S. College, Dehradun, U.P., India and K. R. KAR and K. B. PANDEYA Department of Chemistry, University of Delhi, Delhi-110007, India (Received 5 July 1978; received for publication 17 November 1978) Abstract--Rate of exchange of Zn(NH3)42+ ion in hydrous zirconium(IV) oxide has been studied at different concentrations in the external solution. Rate of exchange reaction increases with increase in the external concentration of Zn(NH3h2÷ ions in the range 0.01-0.10 M; a further increase in the concentration does not affect the second stage of the exchange reaction. Amongst the amine complexes of Ni2+, Cu2+, Zn 2+ and Cd2+ (studied under similar experimental conditions) the decreasing order of rate is: Zn(NH3)42+> Cd(NH3)42+> Cu(NH3)42+> Ni(NI-13)62÷.
INTRODUCTION Studi¢s on kinetics of ion-exchange reactions are of considerable practical as well as theoretical interest. The present paper deals with the kinetics of ions exchange of some metal-ammines in hydrous zirconium(IV) oxide. The first quantitative measurements[l,2] of the rate of the exchange of ions in granular zirconium(IV) phosphate and oxide showed rapid initial uptake, followed by a slower exchange; the two stages presumably corresponding to surface exchange and diffusion into the interior respectively. From the results reported [3] earlier by Kar et al. it has been indicated that the exchange of a few selected divalent cationic ammine complexes of Zn 2+, Cd 2+, Cu 2÷ and Ni 2+ ions in hydrous ZrO2 is time dependent. It is widely accepted that the exchange rates are the characteristics of the exchanging ions and the exchanger materials. The present investigation was particularly undertaken with the object of elucidating the respective roles played by the exchanging ions in determining the exchange rates. The investigation includes, in brief, the study of (i) dependence of exchange rate on the concentration of the exchanging ions, and (ii) effect of the size and shape of the exchanging ions on the rates process. EXPERIMENTAL All the reagents used, unless otherwise stated, were of AR quality. Doubly distilled water was used for the entire experimental work. Hydrous ZrO2. It was prepared by the method described by Amphlett[ll and finally dried at 50--60°. On the basis of the experiments, it has been confirmed that the samples of hydrous ZrO2 used in the present investigation were structurally and otherwise similar to the sample of Amphlett. Determination of the particle radius. ZrO2 particles of average radius 1.1 × 10-2cm were obtained by grinding and sieving the exchanger material through the standard sieves of B.S.S. quality. Finally, the particle radius was checked by the comparator (Nicon Company, Japan).
Metal complexes. Ammine complexes of the selected bivalent transition metals were prepared by dissolving appropriate quantities of the water soluble metal salts in aqueous ammonia (25%) containing 1.0 M NH4CI and then adjusting pH of the homogeneous mixture to 8.5 by the addition of 0.1 M NI-hOH. Determination of the rate of exchange. 25 ml of the stock solution containing the test metal ion under the specified conditions was added to a stoppered conical flask (pyrex quality) containing 250rag of the exchanger material and mechanically shaken for the specified time intervals. The aliquots of the centrifused supernatant solutions were titrated[4] or counted[5] (as the case may be) to know the amount of the metal ion remaining in the supematant solution. From this and the initially known concentration of the metal ion, the amount taken up by the exchanger material was found out. The fractional attainment of equilibrium, F, at time t, was calculated by the relation: Amount of the metal ion exchanged at time t F = Total amount of the metal ion exchanged at equilibrium" Determination of the metal content. The cationic concentration of the solutions has been determined by complexometriic method [4] or radiometric method 15l. In complexometric method 5-10ml portions of the solution containing a test metal ion was buffered to pH - 10 and titrated against 0.02 M standard EDTA solution using a metal indicator (murexide for Cu2÷ and Ni2+ and Eriochrome Black T for Cd2+). Radiometric method was employed only for Zn2+ ions. For determining the concentration of Zn2+ ions by radiometric method, liquid counting technique in conjunction with a Philips Decatron Scalar was adopted. RESULTS AND DISCUSSION The results presented in Tables I-5 and Figs. I and 2 bring out the following facts: (i) The overall exchange takes place in two distinct phases; a relatively quick exchange in the first stage is followed by a slower one, till the equilibrium is reached. (ii) F(t) values increase as the external concentration of the exchanging ions is increased gradually from 0.01 to 0.I0 M. Further, the second phase of the rate process becomes independent of concentration of the exchanging ions above 0.I0 M.
1183
1184
R.K. SRIVASTAVA et al. Table 1. Sorption rate of Zn(NH3h 2+ on ZrO2. Concentration = 0.01 M. Particle radius = 1.1 x 10-2cm. pH =8.5
Table 3. Sorption rate of Zn(NH3h 2+ on ZrO2. Concentration=0.01 M. Particle radius= 1.1 x 10-2cm. Total vol. = 25 ml. pH = 8.5
Time
Amount sorped (m equiv.)
F
Time
Amount sorped (m. equiv.)
F
Bt
30 sec I rain 2 min 5 min 10 min 20 rain 30 rain I hr 2 hr 3 hr
0.087 0.091 0.152 0.193 0.290 0.349 0.373 0.428 0.446 0.460
0.19 0.22 0.33 0.42 0.63 0.76 0.81 0.93 0.97 1.00
30 sec I min 2 rain 5 min 10 min 20 min I hr 2 hr
0.288 0.312 0.336 0.365 0.422 0.460 0.475 0.480
0.60 0.65 0.70 0.76 0.88 0.96 0.99 1.00
0.479 0.594 0.734 0.944 1.623 2.72
Table 2. Sorption rate of Zn(NH3)42+ on ZrO2. Concentration = 0.05 M. Particle radius = 1.1 x 10-2cm. Total vol. = 25 ml. pH = 8.5
--
Table 4. Sorption rate of Zn(NH3)42+ on ZrO2. Concentration = 0.20 M. Particle radius = 1.1 X 10-2 cm. Total vol. -- 25 ml. pH = 8.5
Time
Amount sorped (m equiv.)
F
Time
Amount sorped (m equiv.)
F
30 sec I min 2 min 5 min l0 min 20 min 30 min I hr 2 hr
0.207 0.253 0.276 0.345 0.381 0.405 0.414 0.437 0.460
0.45 0.55 0.60 0.75 0.83 0.86 0.90 0.95 !.00
30 sec I min 2 min 5 min 10 rain 20 rain 30 rain I hr 2 hr
0.302 0.321 0.336 0.365 0.422 0.451 0.461 0.475 0.480
0.63 0.67 0.70 0.76 0.88 0.94 0.96 0.99 1.00
Bt
0.545 0.647 0.734 0.944 1.623 2.320 2.720 4.110 --
Table 5. Exchange rates of Zn(NH3h 2+, Cd(NH3)42+, Cu(NH3)42+ and Ni(NH3)42+ in ZrO2. Concentration of the exchanging ions=0.1 M. Exchanger particle radius=l.lxl0-2cm. Amount of the exchanger particle = 250 rag. pH = 8.5 (NI-hCl)/(Metal ion) = 10 F = Amount exchanged at time t Total amount exchanged Time
Zn-ammine
Cd-ammine
Cu-ammine
Ni-ammine
30 sec I min 2 min 5 min 10 min 20 min 30 min I hr 2 hr 3 hr
0.60 0.65 0.70 0.76 0.88 0.93 0.96 0.99 1.00 1.00
0.45 0.52 0.55 0.70 0.80 0.84 0.88 0.92 0.98 1.00
0.43 0.52 0.54 0.66 0.75 0.83 0.86 0.93 0.96 1.00
0.33 0.40 0.50 0.62 0.73 0.81 0.85 0.91 0.95 0.98
4 hr
i.00
1.00
!.00
1.00
(iii) Various ammine complexes studied follow the following order of the exchange rate: Zn (ammine) > Cd (ammine) > Cu (ammine) > Ni (ammine). It has now been well established[6, 7] that the rate of exchange is governed by the diffusion of the ions, either through the liquid film, surrounding the exchanger material or through the exchanger particles. The farmer is considered to control the rate process in dilute solutions (~<0.01 M), and the later at higher concentrations of the exchanging ions (~0.10 M). In the intermediate con-
centration ranges both the diffusion mechanisms determine the rate process. From Fig. 1 it is clear that the first phase of the exchange rate is dependent on the concentration of the exchanging ions and attains a limiting value at and above 0.10 M concentration, while the rate at the second stage becomes independent of concentration at and above 0.10 M. A reference to the B t vs t curve (Fig. 2) shows that the plots corresponding to the later part of the sorption lies on a straight line, an extrapolation of which intersects the B t axis at 1.3 corresponding to 85% of the equilibrium exchange at hydrous zirconium(IV) dioxide.
Kinetics of ion exchange in hydrous zirconium(IV)oxide iO
////
F
o61~lll
-o
o-
"~
'~
r u!
~_
o. 05
~0
I. Zn-Ammine 2. Cd-Ammine
,_ 3. C u - A ~
20
50
40
50
Time, min
60
Fig. 1. Plot of F vs time. Ideally, the curve for the complete particle diffusion according to the general equation[8]: 6
n=~
[- 7 r 2 D l ' n
1
=
rz
\
2"~
]'
where 7r2D/r 2= B (known as time coordinate), is a straight line passing through the origin. It is, therefore, inferred that the straight line portion of the B t vs t curve represents only the particle diffusion while the preceding part corresponds to the film diffusion. In order to understand the observed sequence in the order of the exchange rates of the ammine complexes hydrous ZrO2, it is necessary to bear in mind that the exchanging ions, being coordination complexes, are appreciably larger than the corresponding uncomplexed species; consequently they are expected to be free from
50
40
1185
hydration effects in aqueous solutions. Further the complex ions being of different symmetry will have different sizes although the formal ionic charge is the same in all the cases. Thus assuming that the complexes are not hydrated, the ionic potential[9] (~=charge/radius) which determines the basicity characteristics of the ions, would vary with size of the exchanging ions. A close look into the observed data under varying experimental conditions leads us to postulate that, other factors remaining the same, the rate at which the exchange reaction takes place is dependent on the ionic potential; the higher the ionic potential the faster is the rate at which the exchange takes place. In the light of this postulate the observed variation in the rate of the exchange of the ions may be examined. The ammine series of complexes have identical formal charge, but in the absence of definite knowledge as to the structural data of the complex species in aqueous solu.tion, it may not be unreasonable to make some qualita-tive estimation of the ionic sizes on the basis of theh' known symmetry and simple ionic radius[10, l l]--Cu 2+, 0.72/~; Zn2+, 0.74/~; Ni 2+, 0.78/~ and Cd 2+, 0.97,~. Because of the known difference in the symmetry of the. ammines[li], dimensions of the simple ions will not., however, solely determine the size of the complex species. Obviously, the tetrahedral symmetry involves a more compact structure than either of square planner or octahedral symmetries. In view of this the expected order of the ionic size of the ammine complexes would be: Zn (Tetrahedral) < Cd (Tetrahedral) < Cu (Square Plannar)< Ni (Octahedral). Consequently, the 4) values will be in the reverse order, i.e. Zn (Tetrahedral)> Cd (Tetrahedral)> Cu (Square Plannar) > Ni (Octahedral). The observed order of the rate of exchange is in agreement with the above mentioned order of ~ values. CONCLUSION From the above investigation we conclude that the exchange quantity (reported earlier[3]) and the rate o1! exchange of the exchanging ions, keeping the other factors constant, is determined by the ionic potential of the exchanging ions; higher the value of the ionic potential, ~b, faster the exchange rate.
REFERENCES 3O
Bt
!
zc I
f
/I/,
, o I 0
I rO
I 20
, 50 Time,
I 40
I 50
I 60
rain
Fig. 2. Plot of Bt vs time for Zn-ammine. I. 0.20M; 2. 0.10M.
1. C. B. Amphlett, L. A. McDonaldand M. J. Redman,J. Inorg. Nucl. Chem. 6, 236 (1958). 2. C. B. Amphlett, L. A. McDonald and M. J. Redman, J. Inorg. Nucl. Chem. 6, 220 (1958). 3. K. R. Kar and R. K. Srivastava, Ind. J. Chem. 11. 1165 (1973). 4. H. A. Flaschka, EDTA Titrations. Pergamon Press. Oxford (1964). 5. K. R. Kar and S. Singh, Microchim. Acta (Wien! 2. 279 (1970). 6. D. Reichenberg,J. Am. Chem. Soc. 75, 589 (1953). 7. F. Helfferich, Ion Exchange. McGraw-Hill,New York (1962). 8. G. E. Boyd, A. W. Adamson and L. S. Myers, J. Am. Chem. Soc. 69, 2836 (1947). 9. G. H. Cartledge, J. Am. Chem. Soc. 5, 2855 (1928). 10. C. K. Jorgensen, Inorganic Complexes. Chap. 4. Academic Press, London (1963). I1. F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry. Wiley-Eastern, New Delhi (1970).
0022-1902/79/0801-11831502.0010
KINETICS OF ION EXCHANGE OF SOME METAL AMMINES IN HYDROUS ZIRCONIUM(IV) OXIDE R. K. SRIVASTAVA and B. PAL Department of Chemistry, D.B.S. College, Dehradun, U.P., India and K. R. KAR and K. B. PANDEYA Department of Chemistry, University of Delhi, Delhi-110007, India (Received 5 July 1978; received for publication 17 November 1978) Abstract--Rate of exchange of Zn(NH3)42+ ion in hydrous zirconium(IV) oxide has been studied at different concentrations in the external solution. Rate of exchange reaction increases with increase in the external concentration of Zn(NH3h2÷ ions in the range 0.01-0.10 M; a further increase in the concentration does not affect the second stage of the exchange reaction. Amongst the amine complexes of Ni2+, Cu2+, Zn 2+ and Cd2+ (studied under similar experimental conditions) the decreasing order of rate is: Zn(NH3)42+> Cd(NH3)42+> Cu(NH3)42+> Ni(NI-13)62÷.
INTRODUCTION Studi¢s on kinetics of ion-exchange reactions are of considerable practical as well as theoretical interest. The present paper deals with the kinetics of ions exchange of some metal-ammines in hydrous zirconium(IV) oxide. The first quantitative measurements[l,2] of the rate of the exchange of ions in granular zirconium(IV) phosphate and oxide showed rapid initial uptake, followed by a slower exchange; the two stages presumably corresponding to surface exchange and diffusion into the interior respectively. From the results reported [3] earlier by Kar et al. it has been indicated that the exchange of a few selected divalent cationic ammine complexes of Zn 2+, Cd 2+, Cu 2÷ and Ni 2+ ions in hydrous ZrO2 is time dependent. It is widely accepted that the exchange rates are the characteristics of the exchanging ions and the exchanger materials. The present investigation was particularly undertaken with the object of elucidating the respective roles played by the exchanging ions in determining the exchange rates. The investigation includes, in brief, the study of (i) dependence of exchange rate on the concentration of the exchanging ions, and (ii) effect of the size and shape of the exchanging ions on the rates process. EXPERIMENTAL All the reagents used, unless otherwise stated, were of AR quality. Doubly distilled water was used for the entire experimental work. Hydrous ZrO2. It was prepared by the method described by Amphlett[ll and finally dried at 50--60°. On the basis of the experiments, it has been confirmed that the samples of hydrous ZrO2 used in the present investigation were structurally and otherwise similar to the sample of Amphlett. Determination of the particle radius. ZrO2 particles of average radius 1.1 × 10-2cm were obtained by grinding and sieving the exchanger material through the standard sieves of B.S.S. quality. Finally, the particle radius was checked by the comparator (Nicon Company, Japan).
Metal complexes. Ammine complexes of the selected bivalent transition metals were prepared by dissolving appropriate quantities of the water soluble metal salts in aqueous ammonia (25%) containing 1.0 M NH4CI and then adjusting pH of the homogeneous mixture to 8.5 by the addition of 0.1 M NI-hOH. Determination of the rate of exchange. 25 ml of the stock solution containing the test metal ion under the specified conditions was added to a stoppered conical flask (pyrex quality) containing 250rag of the exchanger material and mechanically shaken for the specified time intervals. The aliquots of the centrifused supernatant solutions were titrated[4] or counted[5] (as the case may be) to know the amount of the metal ion remaining in the supematant solution. From this and the initially known concentration of the metal ion, the amount taken up by the exchanger material was found out. The fractional attainment of equilibrium, F, at time t, was calculated by the relation: Amount of the metal ion exchanged at time t F = Total amount of the metal ion exchanged at equilibrium" Determination of the metal content. The cationic concentration of the solutions has been determined by complexometriic method [4] or radiometric method 15l. In complexometric method 5-10ml portions of the solution containing a test metal ion was buffered to pH - 10 and titrated against 0.02 M standard EDTA solution using a metal indicator (murexide for Cu2÷ and Ni2+ and Eriochrome Black T for Cd2+). Radiometric method was employed only for Zn2+ ions. For determining the concentration of Zn2+ ions by radiometric method, liquid counting technique in conjunction with a Philips Decatron Scalar was adopted. RESULTS AND DISCUSSION The results presented in Tables I-5 and Figs. I and 2 bring out the following facts: (i) The overall exchange takes place in two distinct phases; a relatively quick exchange in the first stage is followed by a slower one, till the equilibrium is reached. (ii) F(t) values increase as the external concentration of the exchanging ions is increased gradually from 0.01 to 0.I0 M. Further, the second phase of the rate process becomes independent of concentration of the exchanging ions above 0.I0 M.
1183
1184
R.K. SRIVASTAVA et al. Table 1. Sorption rate of Zn(NH3h 2+ on ZrO2. Concentration = 0.01 M. Particle radius = 1.1 x 10-2cm. pH =8.5
Table 3. Sorption rate of Zn(NH3h 2+ on ZrO2. Concentration=0.01 M. Particle radius= 1.1 x 10-2cm. Total vol. = 25 ml. pH = 8.5
Time
Amount sorped (m equiv.)
F
Time
Amount sorped (m. equiv.)
F
Bt
30 sec I rain 2 min 5 min 10 min 20 rain 30 rain I hr 2 hr 3 hr
0.087 0.091 0.152 0.193 0.290 0.349 0.373 0.428 0.446 0.460
0.19 0.22 0.33 0.42 0.63 0.76 0.81 0.93 0.97 1.00
30 sec I min 2 rain 5 min 10 min 20 min I hr 2 hr
0.288 0.312 0.336 0.365 0.422 0.460 0.475 0.480
0.60 0.65 0.70 0.76 0.88 0.96 0.99 1.00
0.479 0.594 0.734 0.944 1.623 2.72
Table 2. Sorption rate of Zn(NH3)42+ on ZrO2. Concentration = 0.05 M. Particle radius = 1.1 x 10-2cm. Total vol. = 25 ml. pH = 8.5
--
Table 4. Sorption rate of Zn(NH3)42+ on ZrO2. Concentration = 0.20 M. Particle radius = 1.1 X 10-2 cm. Total vol. -- 25 ml. pH = 8.5
Time
Amount sorped (m equiv.)
F
Time
Amount sorped (m equiv.)
F
30 sec I min 2 min 5 min l0 min 20 min 30 min I hr 2 hr
0.207 0.253 0.276 0.345 0.381 0.405 0.414 0.437 0.460
0.45 0.55 0.60 0.75 0.83 0.86 0.90 0.95 !.00
30 sec I min 2 min 5 min 10 rain 20 rain 30 rain I hr 2 hr
0.302 0.321 0.336 0.365 0.422 0.451 0.461 0.475 0.480
0.63 0.67 0.70 0.76 0.88 0.94 0.96 0.99 1.00
Bt
0.545 0.647 0.734 0.944 1.623 2.320 2.720 4.110 --
Table 5. Exchange rates of Zn(NH3h 2+, Cd(NH3)42+, Cu(NH3)42+ and Ni(NH3)42+ in ZrO2. Concentration of the exchanging ions=0.1 M. Exchanger particle radius=l.lxl0-2cm. Amount of the exchanger particle = 250 rag. pH = 8.5 (NI-hCl)/(Metal ion) = 10 F = Amount exchanged at time t Total amount exchanged Time
Zn-ammine
Cd-ammine
Cu-ammine
Ni-ammine
30 sec I min 2 min 5 min 10 min 20 min 30 min I hr 2 hr 3 hr
0.60 0.65 0.70 0.76 0.88 0.93 0.96 0.99 1.00 1.00
0.45 0.52 0.55 0.70 0.80 0.84 0.88 0.92 0.98 1.00
0.43 0.52 0.54 0.66 0.75 0.83 0.86 0.93 0.96 1.00
0.33 0.40 0.50 0.62 0.73 0.81 0.85 0.91 0.95 0.98
4 hr
i.00
1.00
!.00
1.00
(iii) Various ammine complexes studied follow the following order of the exchange rate: Zn (ammine) > Cd (ammine) > Cu (ammine) > Ni (ammine). It has now been well established[6, 7] that the rate of exchange is governed by the diffusion of the ions, either through the liquid film, surrounding the exchanger material or through the exchanger particles. The farmer is considered to control the rate process in dilute solutions (~<0.01 M), and the later at higher concentrations of the exchanging ions (~0.10 M). In the intermediate con-
centration ranges both the diffusion mechanisms determine the rate process. From Fig. 1 it is clear that the first phase of the exchange rate is dependent on the concentration of the exchanging ions and attains a limiting value at and above 0.10 M concentration, while the rate at the second stage becomes independent of concentration at and above 0.10 M. A reference to the B t vs t curve (Fig. 2) shows that the plots corresponding to the later part of the sorption lies on a straight line, an extrapolation of which intersects the B t axis at 1.3 corresponding to 85% of the equilibrium exchange at hydrous zirconium(IV) dioxide.
Kinetics of ion exchange in hydrous zirconium(IV)oxide iO
////
F
o61~lll
-o
o-
"~
'~
r u!
~_
o. 05
~0
I. Zn-Ammine 2. Cd-Ammine
,_ 3. C u - A ~
20
50
40
50
Time, min
60
Fig. 1. Plot of F vs time. Ideally, the curve for the complete particle diffusion according to the general equation[8]: 6
n=~
[- 7 r 2 D l ' n
1
=
rz
\
2"~
]'
where 7r2D/r 2= B (known as time coordinate), is a straight line passing through the origin. It is, therefore, inferred that the straight line portion of the B t vs t curve represents only the particle diffusion while the preceding part corresponds to the film diffusion. In order to understand the observed sequence in the order of the exchange rates of the ammine complexes hydrous ZrO2, it is necessary to bear in mind that the exchanging ions, being coordination complexes, are appreciably larger than the corresponding uncomplexed species; consequently they are expected to be free from
50
40
1185
hydration effects in aqueous solutions. Further the complex ions being of different symmetry will have different sizes although the formal ionic charge is the same in all the cases. Thus assuming that the complexes are not hydrated, the ionic potential[9] (~=charge/radius) which determines the basicity characteristics of the ions, would vary with size of the exchanging ions. A close look into the observed data under varying experimental conditions leads us to postulate that, other factors remaining the same, the rate at which the exchange reaction takes place is dependent on the ionic potential; the higher the ionic potential the faster is the rate at which the exchange takes place. In the light of this postulate the observed variation in the rate of the exchange of the ions may be examined. The ammine series of complexes have identical formal charge, but in the absence of definite knowledge as to the structural data of the complex species in aqueous solu.tion, it may not be unreasonable to make some qualita-tive estimation of the ionic sizes on the basis of theh' known symmetry and simple ionic radius[10, l l]--Cu 2+, 0.72/~; Zn2+, 0.74/~; Ni 2+, 0.78/~ and Cd 2+, 0.97,~. Because of the known difference in the symmetry of the. ammines[li], dimensions of the simple ions will not., however, solely determine the size of the complex species. Obviously, the tetrahedral symmetry involves a more compact structure than either of square planner or octahedral symmetries. In view of this the expected order of the ionic size of the ammine complexes would be: Zn (Tetrahedral) < Cd (Tetrahedral) < Cu (Square Plannar)< Ni (Octahedral). Consequently, the 4) values will be in the reverse order, i.e. Zn (Tetrahedral)> Cd (Tetrahedral)> Cu (Square Plannar) > Ni (Octahedral). The observed order of the rate of exchange is in agreement with the above mentioned order of ~ values. CONCLUSION From the above investigation we conclude that the exchange quantity (reported earlier[3]) and the rate o1! exchange of the exchanging ions, keeping the other factors constant, is determined by the ionic potential of the exchanging ions; higher the value of the ionic potential, ~b, faster the exchange rate.
REFERENCES 3O
Bt
!
zc I
f
/I/,
, o I 0
I rO
I 20
, 50 Time,
I 40
I 50
I 60
rain
Fig. 2. Plot of Bt vs time for Zn-ammine. I. 0.20M; 2. 0.10M.
1. C. B. Amphlett, L. A. McDonaldand M. J. Redman,J. Inorg. Nucl. Chem. 6, 236 (1958). 2. C. B. Amphlett, L. A. McDonald and M. J. Redman, J. Inorg. Nucl. Chem. 6, 220 (1958). 3. K. R. Kar and R. K. Srivastava, Ind. J. Chem. 11. 1165 (1973). 4. H. A. Flaschka, EDTA Titrations. Pergamon Press. Oxford (1964). 5. K. R. Kar and S. Singh, Microchim. Acta (Wien! 2. 279 (1970). 6. D. Reichenberg,J. Am. Chem. Soc. 75, 589 (1953). 7. F. Helfferich, Ion Exchange. McGraw-Hill,New York (1962). 8. G. E. Boyd, A. W. Adamson and L. S. Myers, J. Am. Chem. Soc. 69, 2836 (1947). 9. G. H. Cartledge, J. Am. Chem. Soc. 5, 2855 (1928). 10. C. K. Jorgensen, Inorganic Complexes. Chap. 4. Academic Press, London (1963). I1. F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry. Wiley-Eastern, New Delhi (1970).