and the following papers on tartaric acid and acidic tartrates extends our previous studies dealing with the limiting conductivities of citric acid r and succinic acid.
Journal of Solution Chemistry, VoL 26, No. 2, 1997
Conductivity Studies on Aqueous Solutions of Stereoisomers of Tartaric Acids and Tartrates. Part I. Alkali Metal and Ammonium Tartrates Marija Bester-Rogae, 1~ Roland Neueder, 1 Josef Barthel, 1'* and Alexander Apelblat 2 Received June 14, 1996; revised November 16, 1996 Conductivity measurements on aqueous solutions of disodium tartrate, dipotasslum tartrate, sodium potassium tartrate, and diammonium tartrate were performed in the temperature range 5 to 35~ The equivalent limiting conductivity of tartrate anion, k| Tar2-) is evaluated. KEY WORDS: Temperature dependence of conductivity; ion conductivities; aqueous solutions; alkali metal tartrates; ammonium tartrate.
1. INTRODUCTION In spite of the fact that many carboxylic and hydroxycarboxylic acids play an important role in biological and industrial processes, reasonably precise evaluations of the limiting equivalent conductivities of weak, dibasic and tribasic organic acids are rather scarce3 t) This work on neutral tartrates and the following papers on tartaric acid and acidic tartrates extends our previous studies dealing with the limiting conductivities of citric acid r and succinic acid. ~ In this paper the temperature-dependent conductivity (5~176 of dilute aqueous solutions of disodium tartrate, dipotassium tartrate, potassium sodium tartrate, and diammonium tartrate was determined to yield reliable 11nstitut far Physikalische und Theoretische Chemie, Universit~it Regensburg, D-93040 Regensburg, Germany. 2Department of Chemical Engineering, Ben Gurion University of the Negev, Beer Sheva, Israel. 3present affiliation: Dr. M. Bester-Rogac, Department Chemistry and Chemical Technology, University of Ljubljana. 127 0095-9782/97/0200-0127512.50/0 9 1997 Plenum Publishing Corporation
128
Bester-Rogac et al.
temperature-dependent single ion limiting conductivities of the tartrate ion, h~(l/2 Tar~-). 2. E X P E R I M E N T A L
The reagents disodium tartrate (dihydrate), Na2C4H406"2H20, [610624-7], dipotassium tartrate (hemihydrate), K2C4H406"0.5H20, [921-53-9], potassium sodium tartrate (tetrahydrate), KNaC4H406"4H20, [304-59-6] and diammonium tartrate, (NH4)2C4H406 [3164-29-2] were obtained from Fluka (Biochemika Micro Select) and used without further purification. Conductivity water (water purification system, Millipore) with a specific conductance of 7 • -8 S-cm -l (25~ was used for the measurements. Conductivity was determined using a three-electrode measuring cell calibrated with dilute potassium chloride solutions. (4) At the beginning of every measuring series the cell was filled with a weighed amount of solvent. After measurement of the solvent conductivity at all temperatures of the program, 5, 10, 15, 25, 30, 35~ weighed amounts of a stock solution of the studied salt were added using a gas-tight syringe; the temperature program was executed after every addition. The measuring equipment and the measuring procedure, including the extrapolation method of the sample conductivity to infinite frequency, have already been published35-7) The molar concentrations c (mol-dm -3 of solution) were determined from the masses and the corresponding solution densities d calculated with the help of the equations c(T) = r~(T); d(T) = do(T) + Drh,
(la, b)
where do(T) is the solvent density at temperature T as given in Table I. Table I. Densitiesd, Viscosities "q, Dielectric constants ~, of Pure Water and Limiting Equivalent Conductivities of Ions in Watery
T 278.15 283.15 288.15 293.15 298.15 303.15 308.15
do~
"q"103b
0.99997 1.5192 0.99970 1.3069 0.99910 1.1382 0.99821 1.0020 0.99705 0.8903 0.99565 0.7975 0.99404 0.7195
r 85.897 83.945 82.039 80.176 78.358 76.581 74.846
k| 30.30 34.88 39.72 44.81 50.15 55.72 61.53
h=(K+)a h| 46.72 53.03 59.61 66.44 73.50 80.76 88.20
)e 45.94 52.14 58.73 65.72 73.55 80.79 88.72
h~(H+)d 250.02 275.55 300.74 325.52 349.85 373.66 396.90
aRef. 9. bRef. 10. "Ref. 11. aRef. 12. eThe data of Robinson and Stokes Ref. 14 at 0, 18, 25, 35, and 100~ are used to obtain the equation ~Y(NH+) = 5646.6123 + 5.80785 T - 1282.1463 In T. With the help of this equation h~(NI-I~)-valueshave been calculated at other temperatures. YUnits: T: K; do: kg-dm-3; "q: Pa-s; ~: -; h~: S-cm2-mol-t.
Conductivity of Tartrates
129
The temperature-independent density gradients D (obtained from density measurements on solutions and pure water using a Paar vibrating tube densimeter and the method of Kratky et al. (8)) are 0.1371 kg2-mol-l-dm-3 (NazTar), 0.1481 (K2Tar), 0.1420 (KNaTar), 0.0819 ((NHn)2Tar),r~ is the molonity of the electrolyte (moles of solute per kilogram of solution). The physical properties of water are presented in Table I. Also included in Table I are the limiting conductivities of the cations in aqueous solutions known from the literature. 3. RESULTS AND DISCUSSION The results of the conductivity measurements are presented in Table II. In Fig. 1 the equivalent conductivities A at 25~ are plotted as a function of the square root of the ionic strength I. They are presented together with the Topp and Davies conductivities of diammonium tartrate at the same temperature (~3) which have a similar slope, but are shifted to higher values with a regard to our results. The measurements of the present study are more accurate because the equivalent limiting conductances of potassium ion, k~(K +) = 73.50 S-cmZ-mol -l, and ammonium ion, k~(NH~-) = 73.55, are almost equal (Table I) and therefore, the limiting value A ~ of both tartrates also should be equal to yield the same value of k~(l/2 Tara-). Data analysis of the equivalent conductivities of neutral tartrates was executed using the Quint-Viallard-equations, (~7-19) the conductivity equation including the Ec log c term by Onsager and- Klm, --. (2o) and the Onsager limiting law Eqs. (2a-2g) which all yield equal values for the limiting equivalent conductivities within the range of the experimental uncertainty (0.05%). Therefore, the results of the numerically simplest Onsager limiting law are presented in this paper. A = A = - S,,/I
(2a)
A ~ = )t~(M +) + k~(l/2 Tar 2-)
(2b)
S = etA ~~ + 13
(2c)
ot =
1.1437 x 1061zizjl(Izizjlv)l/Zq (eT)3/2( 1 + .,/~)
(2d)
13 =
1.6836(Izi I + Izjl) + (tZiZjlv) 1/2 xI(eT) U2
(2e)
q =
I =
Iz~zjI(x? + xT) ([zil + Izjl)(Izjlk? + Izilkj) 2
c
(2f)
(2g)
Bester-Rogae et al.
130
Table II. Experimental Equivalent Conductivities of Disodium Tartrate, Dipotassium Tartrate, Sodium Potassium Tartrate, and Diammonium Tartrate in the 278.15 to 308.15 K Temperature Range
104r~ mol-kg -I
278.15
283.15
288.15
293.15
298.15
0.5148 1.0290 1.6570 3.2034 5.3958 7.7325 10.7870 15.3427 21.1744 27.3273
65.16 64.96 64.52 63.80 63.03 62.39 61.69 60.88 60.04 59.28
A(I/2 Na2Tar)/(S-cm2-equiv -I) 75.35 86.09 97.24 109.21 75.04 85.71 96.90 108.64 74.55 85.15 96.28 107.96 73.69 84.17 95.14 106.70 72.81 83.16 94.01 105.42 72.06 82.29 93.03 104.32 71.25 81.37 91.99 103.15 70.32 80.27 90.74 101.74 69.33 79.15 89.43 100.21 68.46 78.16 88.35 99.05
121.46 120.84 120.07 118.70 117.26 116.10 114.69 113.16 111.43 110.15
134.20 133.57 132.72 131.07 129.57 128.20 126.75 125.00 123.67 121.67
0.5367 1.0835 2.0163 3.1798 5.0993 7.7359 10.9535 15.7460 21.0188 27.9100
81.58 80.97 80.35 79.83 79.08 78.23 77.46 76.50 75.67 74.73
A(I/2 93.44 92.75 92.03 91.42 90.55 89.59 88.67 87.58 86.62 85.54
146.21 145.16 144.05 143.07 141.65 140.11 138.65 136.89 135.33 133.26
160.57 159.43 158.19 157.09 155.55 153.84 152.21 150.27 148.56 146.28
0.5295 1.5270 3.0450 5.1463 7.8036 10.8402 15.7978 21.4094 27.9222
73.02 72.41 71.64 70.89 70.01 69.45 68.53 67.75 66.89
A(1/2 NaKTar)/(S-cmZ-equiv 83.97 95.50 107.56 83.25 94.68 106.63 82.36 93.66 105.47 81.50 92.65 104.33 80.62 91.65 103.21 79.84 90.76 102.18 78.75 89.53 100.78 77.87 88.52 99.63 76.90 87.41 98.38
l) 120.16 119.11 117.83 116.54 115.28 114.12 112.53 111.25 109.85
133.21 132.05 130.59 129.16 127.76 126.48 124.68 123.28 121.70
146.73 145.46 143.84 142.24 140.68 139.26 137.26 135.71 134.03
0.5341 1.5749 3.0888 5.1263 7.7698 11.1023 16.0007 21.2280 28.3168
80.95 80.80 79.19 78.44 77.60 76.79 75.83 75.01 74.06
A( 1/2(NH4)2Tar)/(S -cm2-equiv 92.91 105.51 118.67 91.80 104.20 117.11 90.86 103.12 115.88 89.98 102.10 114.73 89.01 101.01 113.49 88.07 99.91 112.25 86.95 98.62 110.78 86.00 97.54 109.56 84.90 96.28 108.13
I) 132.28 130.58 129.20 127.89 126.46 125.11 123.47 122.07 120.48
146.51 144.49 142.96 141.47 139.85 138.37 136.55 134.98 133.19
161.13 158.84 157.12 155.46 153.71 152.05 149.99 148.26 146.31
K2Tar))/(S-cm2-equiv -~) 105.87 118.82 132.31 105.10 117.96 131.35 104.28 117.04 130.31 103.58 116.26 129.46 102.59 115.12 128.18 101.50 113.90 126.79 100.45 112.70 125.47 99.16 111.32 123.91 98.11 110.08 122.51 96.88 108.68 120.87
303.15
308.15
Conductivity of Tartrates
131
140 130 120 2
110 100 90
0
I
I
I
I
0.025
0.05
0.075
0.1
i v'
0.125 m
mol'/2 din- ~'2 Fig. 1. Equivalent conductivities, A(I/2 M2Tar), of alkali metal and ammonium tartrates: (1) K2Tar, (2) (NHa)zTar, (3) KNaTar and (4) Na2Tar at 25~ Literature data by Topp and Davies for (NH4)ETar (2').
zi and zj are valences of the ions, v is the number of ions produced by dissociation of one molecule of electrolyte. The other symbols are explained in Table I. In Eq. (2e) the viscosity "q must be expressed in Pa-s. The ionic strength I for 1:2 electrolytes is I = 3c. The limiting equivalent conductivity of the tartrate anion, k=(1/2 Tar2-), is determined with the help of the known k~(M § values (Table I) from an iterative calculation procedure with Eqs. (2) starting with an initial A = value from an empirical A = f(~/-/) plot and the calculation of h=(1/2 Tar2-) under the assumption of single ion additivity at infinite dilution (12'14) k=(l/2 Tar2-) = A=(I/2 M 2 Tar) - k:~(M+)
(3)
This new value is used in Eq. (2) and the procedure is reproduced until convergence. The results of data analysis for all investigated tartrates are presented in Table III together with standard deviations (N: number of data points). o'= ~]
(AiNP5 ? i'ca'c)z
(4)
The limiting single ion conductivity of the tartrate anion can be calculated with the help of Eq. (3.) The results of Table IV show good agreement of the values stemming from different tartrates, h = is the mean value calculated from the values of the alkali metal tartrates and ammonium tartrate. The temperature dependence of the tartrate ion limiting conductivity is given by the expression k~(l/2 Tar2-) = 3999.50 + 4.4443 T - 923.90 In T
132
Bester-Rogac et aL
Table III.
Limiting Equivalent Conductivities of Tartrates, A| Na2Tar
T 278.15 283.15 288.15 293.15 298.15 303.15 308.15
K2Tar
M2Tar), in Water~
KNaTar
(NH4)2Tar
A~
o"
A~
(r
A~
cr
A~
(r
66.32 76.65 87.57 99.05 111.10 123.62 136.64
0.11 0.12 0.14 0.16 0.19 0.23 0.27
82.43 94.46 107.09 120.25 133.96 148.08 162.70
0.10 0.11 0.12 0.13 0.14 0.11 0.12
74.20 85.35 97.10 109.40 122.26 135.58 149.39
0.12 0.16 0.20 0.24 0.28 0.32 0.38
81.79 93.88 106.60 119.86 133.69 147.97 162.70
0.11 0.13 0.15 0.20 0.24 0.27 0.3l
"Units: T: K; A =, o-: S-cm2-equiv -I. m
The Walden product for the tartrate ion in aqueous solution h~~ Taft-) decreases only slightly with temperature indicating no peculiarity, see Fig. 2. The comparison of our results with literature data is possible only at 25~ With an exception of ~=(1/2 Tare-) = 59.6 S-cm2-eqviv -I quoted by Milazzo (15)(but unfortunately the source of the Milazzo limiting conductances of tartrate anion is unknown) other published values are higher than our result of 60.49. The Topp and Davies measurements with diammonium tartrate, (~3)as recalculated by us, yield h=(1/2 Tar2-) = 62.7. The disagreement in this case was expected from the discussion of Fig. 1. The values of these authors from the conductances of 2:2 electrolytes are inconsistent: h=(l/2 Tar2-) = 64.7 from calcium tartrate, h~ Tai~-) = 54.7 from barium tartrate conductances. In the original paper the average value of 59.7 was reported. Dippy, Hughes, and Rozanski give k=(1/2 Tar 2-) = 63.19, based on conductances of disodium tartrate, (16) but unfortunately without experimental data permitting the comparison with our measurements. Table IV. Limiting Equivalent Conductivities of Tara- Anion and Walden Product as Function of Temperatures ~ h=(l/2 Tara-) m
T 278.15 283.15 288.15 293.15 298.15 303.15 308.15
NazTar
K2Tar
KNaTar
(NH4)2Tar
k~(l/2 Tar2-)
k = • 2 1 5 103
36.02 41.77 47.86 54.24 60.95 67.90 75.11
35.71 41.43 47.48 53.81 60,46 67,32 74,50
35.69 41.40 47.44 53.78 60.44 67.34 74.52
35.85 41.74 47.87 54.14 60.14 67.18 73.98
35.82 41.58 47.67 53.99 60.49 67.44 74.53
54.42 54.34 54.26 54.10 53.85 53.78 53.62
D
~Units: T: K h ' : S-cm2-equiv-~; h|
S-cm2-equiv-I-Pa-s.
Conductivity of Tartrates
133
55.0
~a 54.5
I~"
54.o
? m
53.5
l
l
280
290
i
300
310
T K Fig. 2. Walden product, h~-q(l/2 Tar2-), of the tartrate anion as function of temperature.
The temperature-dependent single ion conductivities of the aqueous tartrate solutions obtained in this first part of our studies are used in following investigations for the evaluation of electrolyte conductivities of D-tartaric acid, L-tartaric acid, and mesotartaric acid (part II) and acidic tartrates (part III) with the help of the Quint and Viallard t h e o r y ~17-19) of unsymmetrical electrolytes. ACKNOWLEDGMENT The authors are grateful to Alexander von Humboldt-Stiftung for a grant enabling Marija Bester-Rogac to participate in this investigation at the University of Regensburg. REFERENCES A. Apelblat, Current Topics in Solution Chem. 1, 171 (1994). A. Apelblat and J. Barthel, Z. Naturforsch. 46a, 131 (1991). A. Apelblat and J. Barthel, Z. Naturforsch. 47a, 493 (1992). J. Barthel, E Feuerlein, R. Neueder, and R. Wachter, J. Solution Chem. 9, 209 (1980). J. Barthel, H. J. Gores, and G. Schmeer, Ber. Bunsenges. Phys. Chem. 83, 911 (1979). J. Barthel, R. Wachter, and H. J. Gores, in B. E. Conway and J. O.'M. Bockris, eds., Vol. 13, Modern Aspects of Electrochemistry, (Plenum Press, New York, 1979). 7. R. Wachter and J. Barthel, Ber. Bunsenges. Phys. Chem. 83, 634 (1979). 8. O. Kratky, H. Leopold, and H. Stabinger, Z. Angew. Phys. 27, 273 (1969).
1. 2. 3. 4. 5. 6.
9. E. F. G. Herington, ed., Recommended Reference Materials for Realization of Physicochemical Properties, Pure AppL Chem. 48, l (1976). 10. L. Korson, W. Drost-Hansen, and E J. Millero, J. Phys. Chem. 73, 34 (1969). 11. B. B. Owen, R. C. Miller, C. E. Miller, and H. L. Cogan, J. Am. Chem. Soc. 83, 2065 (1961). 12. H. S. Hamed and B. B. Owen, The Physical Chemistry of Electrolytic Solutions, 3rd edn., Reinhold Publ. Corp., New York, 1958. 13. N. E. Topp and C. W. Davies, J. Chem. Soc. 87 (1940).
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14. R. A. Robinson and R. H. Stokes, Electrolyte Solutions, 2nd rev. ed., (Butterworths, London 1970). 15. G. Milazzo, Electrochemistry, (Elsevier, Amsterdam, 1963) p.61. 16. J. E J. Dippy, S. R. C. Hughes, and A. Rozanski, J. Chem. Soc. 2492 (1959). 17. J. Quint and A. Viallard, J. Solution Chem. 7, 137 (1978). 18. J. Quint and A. Viallard, J. Solution Chem. 7, 525 (1978). 19. J. Quint and A. Viallard, J. Solution Chem. 7, 533 (1978). 20. L. Onsager and S. K. Kim, J. Phys. Chem. 61, 215 (1957).
