The audio electrical conductances of aqueous solutions of magnesium, manganese II, barium, and copper succinates have been measured at various temperatures in the range of 298.15 K to 313.15 K, using an audio frequency conductance bridge. The evaluation of conductance data was carried out by minimisation technique using the theoretical equations of the complete and modified forms of Pitts (P) and Fuoss-Hsia (F-H), each a three-parameter equation, association constant (
The conductance of any electrolyte at infinite dilution is generally recognised to be dependent upon temperature, viscosity, and dielectric constant. Also, it is well established that the extent of association of a series of electrolytes in different solvents is specific for any ion-solvent combination, rather than being dielectric constant dependent. Information on ion-ion and ion-solvent and interactions can be obtained from conductivity measurement [
On the other hand, the conductance behavior of 2 : 2 electrolytes (specially salts of dicarboxylic acids) has received relatively little attention. This is largely due to the difficulty encountered in analysing such data since the usual methods require an arbitrary choice for some of the parameters needed in the analysis. However, there were no available cited recent studies in the literature concerning the association of the bivalent cations with bivalent organic ligands. In part I of this paper, we report conductance measurement of magnesium, manganese II, barium, and copper succinates in aqueous medium at various temperatures in the range 298.15–313.15 K. Metal succinates play an important role in biological and industrial processes [
Measurements were made at a range of temperatures between 298.15 and 313.15 K with Oakton-con510 audio frequency bridge of low impedance. It combines speed and simplicity of operation with 0.05% accuracy. The cell used for measuring conductances has been described elsewhere [
The KCl used in this work was purified and used according to the literature [
Manganese succinate was prepared by the method described by Vogel [
The same method [
The copper succinate was prepared by reaction stochiometric amounts of both a solution of succinic acid and copper metal. The solution was heated with continuous stirring at 348.15–353.15 K for a period of 3-4 hours. A blue solution appeared which was evaporated on a water bath after filtering and removing the excess metal copper. The product was a blue powder and dried afterwards for 24 hours, as the dihydrate. Elemental analysis confirmed the composition with experimental/calculated values (mass percent): C 22.3/22.3, H 3.2/3.7. The FT-IR spectra exhibit the following absorption bands (KBr pellet,
All stock solutions were prepared by weight, and all measurements were done using the weight dilution technique.
Figure
FT-IR spectra for Mg succinate.
The measured molar conductances
Experimental conductance data for Ba succinate.
298.15 K | 303.15 K | 308.15 K | 313.15 K | ||||
---|---|---|---|---|---|---|---|
Conc. *103 | Λ | Conc. *103 | Λ | Conc. *103 | Λ | Conc. *103 | Λ |
0.56411 | 199.190 | 0.50910 | 209.414 | 0.70798 | 202.902 | 0.62824 | 208.904 |
0.74531 | 193.356 | 0.62278 | 204.192 | 0.75117 | 201.282 | 0.66546 | 207.388 |
0.79218 | 192.096 | 0.67767 | 202.628 | 0.79106 | 200.014 | 0.70088 | 206.188 |
0.83645 | 191.262 | 0.77676 | 199.560 | 0.82796 | 199.898 | 0.73761 | 204.738 |
0.87756 | 190.604 | 0.82113 | 197.964 | 0.86275 | 197.870 | 0.77281 | 203.830 |
0.91808 | 190.128 | 0.86265 | 195.676 | 0.89685 | 196.440 | 0.80525 | 202.728 |
0.95837 | 189.466 | 0.90303 | 195.570 | 0.93330 | 195.458 | 0.83474 | 202.112 |
1.03271 | 187.164 | 0.97511 | 193.654 | 0.96168 | 194.830 | 0.86236 | 201.070 |
1.09135 | 186.406 | 1.00758 | 192.836 | 0.98779 | 193.896 | 0.88292 | 200.514 |
1.10711 | 186.808 | 1.03740 | 190.804 | 1.01067 | 193.368 | 0.90937 | 199.260 |
1.06599 | 190.326 |
Λ (ohm−1cm2mol−1); Conc.: concentration (mol·dm−3).
Experimental conductance data for Cu succinate.
298.15 K | 303.15 K | 308.15 K | 313.15 K | ||||
---|---|---|---|---|---|---|---|
Conc. *103 | Λ | Conc. *103 | Λ | Conc. *103 | Λ | Conc. *103 | Λ |
0.11875 | 104.322 | 0.22592 | 88.190 | 0.26685 | 83.448 | 0.40075 | 76.194 |
0.17218 | 92.200 | 0.34929 | 73.130 | 0.32137 | 77.388 | 0.45082 | 72.174 |
0.40553 | 66.350 | 0.40233 | 69.116 | 0.37259 | 72.824 | 0.50755 | 68.362 |
0.51577 | 60.392 | 0.45097 | 66.048 | 0.41829 | 69.286 | 0.55875 | 65.358 |
0.57000 | 57.934 | 0.55605 | 60.490 | 0.47100 | 66.172 | 0.60713 | 63.150 |
0.62195 | 56.106 | 0.60216 | 58.582 | 0.51965 | 63.582 | 0.65040 | 61.270 |
0.67296 | 54.482 | 0.69118 | 55.478 | 0.56405 | 61.622 | 0.69433 | 59.530 |
0.72053 | 53.198 | 0.72973 | 54.188 | 0.60434 | 59.882 | 0.73652 | 58.098 |
0.76804 | 52.312 | 0.76627 | 53.302 | 0.64214 | 58.666 | 0.80993 | 55.852 |
0.80697 | 51.142 | 0.79876 | 52.208 | 0.67746 | 57.336 | 0.87104 | 54.114 |
0.84202 | 50.218 | 0.83003 | 51.590 | 0.71418 | 56.100 | 0.89970 | 53.402 |
0.87450 | 49.544 | 0.88436 | 50.392 | 0.78025 | 54.250 | 0.92202 | 52.900 |
0.90625 | 48.870 | 0.90694 | 49.998 | 0.80909 | 53.506 | 0.94071 | 52.430 |
0.93728 | 48.336 | 0.923890 | 49.530 |
Λ (ohm−1cm2mol−1); Conc.: concentration (mol·dm−3).
Experimental conductance data for Mg succinate.
298.15 K | 303.15 K | 308.15 K | 313.15 K | ||||
---|---|---|---|---|---|---|---|
Conc. *103 | Λ | Conc. *103 | Λ | Conc. *103 | Λ | Conc. *103 | Λ |
0.32106 | 152.146 | 0.53293 | 167.682 | 0.56479 | 171.312 | 0.06619 | 222.736 |
0.38543 | 150.700 | 0.62320 | 165.106 | 0.65514 | 166.354 | 0.23327 | 200.850 |
0.44357 | 147.958 | 0.73614 | 159.570 | 0.77615 | 163.214 | 0.52183 | 181.330 |
0.49967 | 144.364 | 0.95818 | 153.276 | 0.88264 | 159.736 | 0.72094 | 172.758 |
0.56965 | 141.704 | 1.07099 | 150.494 | 1.01288 | 157.180 | 0.81690 | 169.664 |
0.63635 | 139.118 | 1.19035 | 147.426 | 1.13065 | 153.924 | 0.93341 | 165.490 |
0.69845 | 136.062 | 1.32226 | 145.708 | 1.25809 | 151.156 | 1.16002 | 160.302 |
0.77167 | 133.942 | 1.44684 | 143.592 | 1.40034 | 148.436 | 1.41143 | 155.162 |
0.83990 | 131.736 | 1.57115 | 142.498 | 1.53116 | 146.800 | 1.53523 | 152.818 |
0.91505 | 129.448 | 1.83767 | 137.972 | 1.66882 | 144.824 | 1.66980 | 149.540 |
Λ (ohm−1cm2mol−1); Conc.: concentration (mol·dm−3).
Experimental conductance data for Mn-succinate.
298.15 K | 303.15 K | 308.15 K | 313.15 K | ||||
---|---|---|---|---|---|---|---|
Conc. *103 | Λ | Conc. *103 | Λ | Conc. *103 | Λ | Conc. *103 | Λ |
0.43244 | 162.542 | 0.19989 | 182.826 | 0.10976 | 197.114 | 0.34023 | 176.396 |
0.51084 | 158.992 | 0.31941 | 171.114 | 0.14567 | 191.570 | 0.39961 | 169.720 |
0.60785 | 153.734 | 0.37725 | 167.640 | 0.33335 | 170.980 | 0.47590 | 167.116 |
0.69413 | 149.622 | 0.46203 | 162.784 | 0.39655 | 167.354 | 0.53986 | 163.222 |
1.01124 | 139.240 | 0.54652 | 159.042 | 0.47351 | 160.484 | 0.61789 | 159.032 |
1.12663 | 135.140 | 1.08379 | 138.060 | 0.54065 | 159.326 | 0.69363 | 155.548 |
1.24575 | 132.034 | 1.20277 | 134.786 | 0.69278 | 148.376 | 0.77113 | 151.386 |
1.37319 | 129.446 | 1.32895 | 131.778 | 0.77883 | 146.682 | 0.85864 | 147.472 |
1.49389 | 127.348 | 1.56919 | 125.532 | 0.87155 | 141.826 | 0.93962 | 146.116 |
1.59976 | 125.100 | 1.69673 | 124.530 | 1.25557 | 131.398 | 1.02234 | 143.202 |
Λ (ohm−1cm2mol−1); Conc.: concentration (mol·dm−3).
Best fit results for Ba-succinate.
Temps. | Parameter | F-H complete* | F-H modified* | Pitts complete | Pitts modified |
---|---|---|---|---|---|
298.15 K | Λ0 | 240.00 | 238.80 | 231.40–232.60 | 236.40 |
|
135.00 | 114.00 | 275.00–285.00 | 78.00 | |
|
0.99 | 1.01 | 0.30 | 0.69 | |
|
1.597 | 1.589 | 1.544 | 1.573 | |
|
0.1859 | 0.2110 | 0.3086 | 0.2727 | |
|
2.13816 | 2.12747 | 2.06689 | 2.10609 | |
| |||||
303.15 K | Λ0 | 261.20 | 259.20 | 250.80–251.00 | 254.20 |
|
182.0 | 216.0 | 380.0–382.0 | 81.0 | |
|
0.70 | 1.39 | 0.30 | 0.70 | |
|
1.767 | 1.754 | 1.698 | 1.720 | |
|
0.2410 | 0.2339 | 0.2867 | 0.2267 | |
|
2.08490 | 2.06893 | 2.00268 | 2.02902 | |
| |||||
308.15 K | Λ0 | 279.80 | 270.00 | 261.60–261.80 | 263.60 |
|
420.0 | 263.0 | 430.0 | 110.0 | |
|
1.41 | 1.39 | 0.70 | 0.30 | |
|
1.916 | 1.857 | 1.800 | 1.813 | |
|
0.1866 | 0.2308 | 0.2889 | 0.2190 | |
|
2.02239 | 1.95156 | 1.89157 | 1.90530 | |
| |||||
313.15 K | Λ0 | 288.80 | 276.00 | 275.20 | 272.00 |
|
455.0 | 264.7 | 540.0 | 150.0 | |
|
1.40 | 1.39 | 0.35 | 0.41 | |
|
2.019 | 1.929 | 1.924 | 1.901 | |
|
0.2509 | 0.3156 | 0.4114 | 0.3189 | |
|
1.88875 | 1.80504 | 1.79981 | 1.77888 |
Units of Λ0: ohm−1cm2mol−1,
Best fit results for Cu-succinate.
Temps. | Parameter | F-H complete* | F-H modified* | Pitts complete | Pitts modified |
---|---|---|---|---|---|
298.15 K | Λ0 | 226.20 | 221.40 | 214.60–215.00 | 217.00 |
|
11600.0 | 10510.0 | 11100.0–11108.0 | 10050.0 | |
|
1.01 | 0.71 | 0.10 | 0.31 | |
|
1.505 | 1.473 | 1.429 | 1.444 | |
|
0.1723 | 0.2198 | 0.2417 | 0.1998 | |
|
2.01522 | 1.97245 | 1.91365 | 1.93325 | |
| |||||
303.15 K | Λ0 | 271.40 | 267.60 | 267.80 and 268.00 | 262.20 |
|
16300.0 | 15020.0 | 17000.0 | 14550.0 | |
|
0.69 | 0.31 | 1.00 | 0.30 | |
|
1.836 | 1.811 | 1.812 | 1.774 | |
|
0.1800 | 0.1971 | 0.2513 | 0.1869 | |
|
2.16632 | 2.13598 | 2.13838 | 2.09288 | |
| |||||
308.15 K | Λ0 | 287.80 | 279.60 | 277.80–278.10 | 280.40 |
|
18100.0 | 15800.0 | 17950.0–18050.0 | 16200.0 | |
|
1.01 | 0.31 | 0.30 | 0.31 | |
|
1.980 | 1.923 | 1.912 | 1.929 | |
|
0.1130 | 0.2095 | 0.2569 | 0.1770 | |
|
2.08022 | 2.02095 | 2.00902 | 2.02673 | |
| |||||
313.15 K | Λ0 | 359.20 | 345.00 | 331.70–332.30 | 344.80 |
|
25300.0 | 22100.0 | 22700.0–22900.0 | 22450.0 | |
|
0.29 | 0.29 | 1.40 | 0.29 | |
|
2.511 | 2.411 | 2.321 | 2.410 | |
|
0.1083 | 0.1027 | 0.2589 | 0.1071 | |
|
2.34917 | 2.25630 | 2.17128 | 2.25500 |
Units of Λ0: ohm−1cm2mol−1,
Best fit results for Mg-succinate.
Temps. | Parameter | F-H complete* | F-H modified* | Pitts complete | Pitts modified |
---|---|---|---|---|---|
298.15 K | Λ0 | 225.20 | 222.60 | 220.00 | 223.00 |
|
120.0 | 170.0 | 320.0 | 110.0 | |
|
0.59 | 1.40 | 0.70 | 0.60 | |
|
1.499 | 1.481 | 1.464 | 1.484 | |
|
0.5177 | 0.2390 | 0.4397 | 0.3709 | |
|
2.00631 | 1.98314 | 1.95998 | 1.98671 | |
| |||||
303.15 K | Λ0 | 230.00 | 229.20 | 228.00 | 228.20 |
|
175.0 | 200.0 | 460.0 | 160.0 | |
|
0.65 | 1.00 | 0.30 | 0.60 | |
|
1.556 | 1.551 | 1.543 | 1.544 | |
|
0.0975 | 0.0961 | 11.4499 | 0.2885 | |
|
1.83586 | 1.82947 | 1.81990 | 1.82149 | |
| |||||
308.15 K | Λ0 | 231.80 | 232.00 | 231.60 | 231.40 |
|
370.0 | 295.0 | 560.0 | 280.0 | |
|
1.00 | 1.00 | 1.40 | 0.70 | |
|
1.594 | 1.596 | 1.593 | 1.592 | |
|
0.3931 | 0.9841 | 1.6379 | 1.3726 | |
|
1.67545 | 1.67690 | 1.67401 | 1.67256 | |
| |||||
313.15 K | Λ0 | 260.00 | 253.20 | 251.20 | 253.80 |
|
480.0 | 329.0 | 592.0 | 305.0 | |
|
1.39 | 1.41 | 1.00 | 1.01 | |
|
1.817 | 1.770 | 1.756 | 1.774 | |
|
0.8112 | 0.6646 | 0.7072 | 0.6792 | |
|
1.70040 | 1.65593 | 1.64285 | 1.65985 |
Units of Λ0: ohm−1cm2mol−1,
Best fit results for Mn-succinate.
Temps. | Parameter | F-H complete* | F-H modified* | Pitts complete | Pitts modified |
---|---|---|---|---|---|
298.15 K | Λ0 | 224.80 | 220.00 | 220.40–220.80 | 223.40 |
|
353.0 | 490.0 | 850.0 | 550.0 | |
|
0.65 | 1.10 | 0.30 | 0.65 | |
|
1.496 | 1.464 | 1.468 | 1.487 | |
|
0.2028 | 0.1772 | 0.3644 | 0.3928 | |
|
2.00274 | 1.95998 | 1.96533 | 1.99027 | |
| |||||
303.15 K | Λ0 | 226.30 | 225.80 | 228.00 | 226.00 |
|
500.0 | 525.0 | 950.0 | 553.0 | |
|
0.60 | 1.20 | 0.30 | 0.75 | |
|
1.531 | 1.528 | 1.543 | 1.530 | |
|
0.4441 | 0.5212 | 0.7283 | 0.8156 | |
|
1.80633 | 1.80234 | 1.81990 | 1.80393 | |
| |||||
308.15 K | Λ0 | 232.80 | 229.80 | 230.60 | 230.00 |
|
680.0 | 580.0 | 990.0 | 555.0 | |
|
1.00 | 1.10 | 0.30 | 0.80 | |
|
1.601 | 1.581 | 1.586 | 1.582 | |
|
0.5795 | 0.4829 | 0.7623 | 0.5641 | |
|
1.68268 | 1.66099 | 1.66678 | 1.66244 | |
| |||||
313.15 K | Λ0 | 246.00 | 239.60 | 240.00 | 242.60 |
|
820.0 | 590.0 | 1010.0 | 585.0 | |
|
1.40 | 1.41 | 0.30 | 0.71 | |
|
1.720 | 1.675 | 1.678 | 1.696 | |
|
0.4200 | 0.5529 | 0.5570 | 0.7734 | |
|
1.60884 | 1.56698 | 1.56960 | 1.58660 |
Units of Λ0: ohm−1cm2mol−1,
Walden product and the corresponding values of the standard deviation
It was noted that the minimisation
It was obvious from the minimisation technique that the parameter
Form the association constants given in Tables
The succinate ion possesses the donor property to a less degree than both oxalate and malonate ions [
In Figures
Molar conductance versus square root of concentration for Ba-succinate at different temperatures.
Molar conductance versus square root of concentration for Cu-succinate at different temperatures.
Molar conductance versus square root of concentration for Mg-succinate at different temperatures.
Molar conductance versus square root of concentration for Mn-succinate at different temperatures.
Considering the difficulties resulting from the limited solubilities of the succinate salts, the values obtained in this work for
It is obvious from Tables (
Recently, an investigation of Mg, Ca, and Ba complexes in aqueous solution was carried out [
Unfortunately, no recent determinations of
In order to obtain a better understanding of the thermodynamics of the association reactions for the studied salts, it is useful to consider the enthalpic and entropic contributions to these associations. The standard enthalpy, free energy and entropy changes were determined by using (
Standard thermodynamic quantities for the association reaction of metal ion (M+2) and succinate ions are obtained from the temperature dependence of
Thermodynamic data for Ba-succinate.
|
|
| |||||||
---|---|---|---|---|---|---|---|---|---|
298.15 K | 303.15 K | 308.15 K | 313.15 K | 298.15 K | 303.15 K | 308.15 K | 313.15 K | ||
F-H complete | 69.681 | −12.159 | −13.116 | −15.475 | −15.934 | 274.493 | 273.122 | 276.346 | 273.400 |
F-H modified | 42.614 | −11.740 | −13.548 | −14.276 | −14.524 | 182.303 | 185.260 | 184.617 | 182.461 |
Pitts complete | 32.510 | −13.968 | −14.978 | −15.535 | −16.380 | 155.887 | 156.647 | 155.913 | 156.122 |
Pitts modified | 35.069 | −10.800 | −11.076 | −12.042 | −13.045 | 153.846 | 152.219 | 152.884 | 153.646 |
Thermodynamic data for Cu-succinate.
|
|
| |||||||
---|---|---|---|---|---|---|---|---|---|
298.15 K | 303.15 K | 308.15 K | 313.15 K | 298.15 K | 303.15 K | 308.15 K | 313.15 K | ||
F-H complete | 37.950 | −23.199 | −24.445 | −25.117 | −26.396 | 168.065 | 168.450 | 173.372 | 172.070 |
F-H modified | 35.414 | −22.954 | −24.239 | −24.768 | −26.044 | 158.155 | 161.510 | 161.252 | 159.469 |
Pitts complete | 34.494 | −23.090 | −24.551 | −25.102 | −26.125 | 162.542 | 163.193 | 162.353 | 162.459 |
Pitts modified | 39.125 | −22.843 | −24.159 | −24.832 | −26.085 | 167.448 | 165.597 | 166.045 | 166.597 |
Thermodynamic data for Mg-succinate.
|
|
| |||||||
---|---|---|---|---|---|---|---|---|---|
298.15 K | 303.15 K | 308.15 K | 313.15 K | 298.15 K | 303.15 K | 308.15 K | 313.15 K | ||
F-H complete | 76.249 | −11.867 | −13.017 | −15.150 | −16.074 | 296.520 | 294.787 | 297.659 | 294.372 |
F-H modified | 36.812 | −12.731 | −13.354 | −14.570 | −15.090 | 162.843 | 166.122 | 165.789 | 163.933 |
Pitts complete | 31.863 | −14.299 | −15.453 | −16.212 | −16.620 | 153.717 | 154.514 | 153.814 | 154.056 |
Pitts modified | 56.333 | −11.652 | −12.791 | −14.436 | −14.893 | 225.165 | 222.361 | 221.888 | 221.548 |
Thermodynamic data for Mn-succinate.
|
|
| |||||||
---|---|---|---|---|---|---|---|---|---|
298.15 K | 303.15 K | 308.15 K | 313.15 K | 298.15 K | 303.15 K | 308.15 K | 313.15 K | ||
F-H complete | 44.111 | −14.542 | −15.663 | −16.709 | −17.468 | 188.730 | 188.774 | 193.366 | 191.745 |
F-H modified | 10.223 | −15.355 | −15.786 | −16.302 | −16.611 | 73.663 | 78.412 | 79.503 | 79.025 |
Pitts complete | 8.720 | −16.720 | −17.281 | −17.672 | −18.010 | 76.095 | 78.171 | 78.710 | 80.152 |
Pitts modified | 2.906 | −15.641 | −15.903 | −16.189 | −16.589 | 45.969 | 46.121 | 48.508 | 50.936 |
The positive entropy values of the associations indicate a change from more order states towards a less order states. This might reflect the role of solvent in the association process.
The above-mentioned results show that the
Many difficulties and uncertainties are associated with these calculations which are derived from the inevitable experimental errors in
From the dependence of the Walden product
Generally, it is concluded that either Fuoss-Hsia complete or modified is better than those equations of Pitts.
With affection and deep appreciation the authors acknowledge their indebtedness to: