Solubility Product of Silver Bromate in Solutions of Zinc and Cadmium Nitrates
Abstract Generated abstract
The study examines how zinc and cadmium nitrates affect the solubility, solubility product, and activity coefficient of silver bromate in ternary aqueous systems at 25°C. Solubility measurements were made gravimetrically over nitrate concentrations from 0.001 to 1 mol/l, and the results were compared with earlier data for magnesium, calcium, strontium, and barium nitrates. In both systems the solubility and solubility product of silver bromate increase regularly with electrolyte concentration, while the activity coefficient decreases. The data indicate that zinc nitrate influences silver bromate behavior approximately like strontium nitrate, whereas cadmium nitrate gives results close to magnesium nitrate, supporting extension of the previously proposed practical calculation method to zinc and cadmium nitrate solutions.
Full Text
SOLUBILITY PRODUCT OF SILVER BROMATE IN SOLUTIONS OF ZINC AND CADMIUM NITRATES
Yu. L. LEL’CHUK
Our earlier study of the effect of magnesium, calcium, strontium, and barium nitrates on the solubility of the silver bromate precipitate enabled us to draw definite conclusions about the dependence of the solubility of the precipitate on the concentration of the external electrolyte and on the position of these metals in the second group of D. I. Mendeleev’s periodic system [1]. The above-mentioned investigation showed with sufficient conclusiveness that the greater the atomic weight of the alkaline-earth metal and the radius of the cation of the external electrolyte, the greater is its effect on the solubility and the solubility product of the precipitate. The difference in the behavior of the silver bromate precipitate in the ternary systems considered becomes especially noticeable at concentrations of the external electrolytes of \(0.1\ \mathrm{mol/l}\) and higher.
The experimental data obtained by us for the ternary systems
\[ \mathrm{AgBrO_3}—\mathrm{Mg(NO_3)_2}—\mathrm{H_2O}, \qquad \mathrm{AgBrO_3}—\mathrm{Ca(NO_3)_2}—\mathrm{H_2O}, \]
\[ \mathrm{AgBrO_3}—\mathrm{Sr(NO_3)_2}—\mathrm{H_2O}\ \text{and}\ \mathrm{AgBrO_3}—\mathrm{Ba(NO_3)_2}—\mathrm{H_2O}, \]
enabled us to determine the extent of the changes in the solubility product of the precipitate in these systems, to calculate the activity coefficients of silver bromate at different concentrations of the external electrolytes, and to propose a formula for calculating, with accuracy sufficient for practical purposes, the solubility of the silver bromate precipitate in aqueous solutions of magnesium, calcium, strontium, and barium nitrates at any electrolyte concentration in the interval from \(0.001\) to \(1\ \mathrm{mol/l}\).
The question of the extent to which our conclusions for magnesium, calcium, strontium, and barium nitrates are valid for other cations of elements of the second group of the periodic system can be resolved only by an additional physicochemical investigation of the solubility in the corresponding ternary systems. In this connection, we have carried out a study of the solubility in the systems \(\mathrm{AgBrO_3}—\mathrm{Zn(NO_3)_2}—\mathrm{H_2O}\) and \(\mathrm{AgBrO_3}—\mathrm{Cd(NO_3)_2}—\mathrm{H_2O}\) at concentrations of zinc and cadmium nitrates of \(0.001,\ 0.003,\ 0.010,\ 0.03,\ 0.1,\ 0.3,\) and \(1\ \mathrm{mol/l}\) at \(25^\circ\mathrm{C}\).
Starting Materials and Method of Investigation
The preparation of chemically pure silver bromate and the method for investigating solubility have been described in detail in the first published communications devoted to the study of the solubility of the silver bromate precipitate in aqueous solutions of nitrates of alkali and alkaline-earth metals [1, 2].
Aqueous solutions of zinc and cadmium nitrates were obtained by appropriate dilution of one-molar solutions of chemically pure \(\mathrm{Zn(NO_3)_2\cdot 6H_2O}\) and \(\mathrm{Cd(NO_3)_2\cdot 4H_2O}\). Preparation and dilution of the molar solutions were carried out with bidistilled water.
Experiments to determine the solubility in these systems were carried out in brown-glass bottles of 400–500 ml capacity. A bottle closed with a cork stopper, containing one gram of silver bromate and 250 ml of a zinc or cadmium nitrate solution of the corresponding concentration, was placed in a water thermostat at a temperature of \(25^\circ\mathrm{C} \pm 0.1^\circ\), where vigorous stirring by a motor was carried out for 8 hours. The temperature in the thermostat was maintained by means of a mercury–toluene thermoregulator.
Before a sample was taken to determine the silver bromate content in the liquid phase, the solution with the precipitate was allowed to stand in the thermostat for 45–50 min. The concentration of silver bromate was determined gravimetrically in the form of silver chloride by the method described by Kolthoff and Sandell [3].
The precipitation and settling of silver chloride were carried out in beakers protected from the action of light by caps made of black paper. Filtration and drying of the weighed form were performed in glass crucibles with a filtering bottom No. 3.
System \(\mathrm{AgBrO_3—Zn(NO_3)_2—H_2O}\)
The experimental data obtained by us for the ternary system silver bromate–zinc nitrate–water are given in Table 1 and are represented graphically in Fig. 1. In the first column of the table are given the molar concentrations of zinc nitrate; in the second, the molar concentrations of silver bromate; in the third, the ionic strengths of the solutions; in the fourth, the activity coefficients of silver bromate; in the fifth, the solubility product of the precipitate; in the sixth, the activity product of silver bromate; in the seventh, the value of the coefficient \(a\) in the Debye and Hückel formula for calculating the activity coefficient of the precipitate at concentrations of foreign electrolytes exceeding the Debye range [4].
Table 1
Solubility of \(\mathrm{AgBrO_3}\) in the system \(\mathrm{AgBrO_3—Zn(NO_3)_2—H_2O}\)
| \(\mathrm{Zn(NO_3)_2}\), mol/l | \(\mathrm{AgBrO_3}\), mol/l | \(\mu\) | \(\gamma\) | \(L_p\) | \(L_a\) | \(a\) |
|---|---|---|---|---|---|---|
| 0.000 | \(8.25 \cdot 10^{-3}\) | 0.0082 | 0.900 | \(6.80 \cdot 10^{-5}\) | \(5.50 \cdot 10^{-5}\) | 1.936 |
| 0.001 | \(8.41 \cdot 10^{-3}\) | 0.0114 | 0.890 | \(7.11 \cdot 10^{-5}\) | \(5.63 \cdot 10^{-5}\) | 1.936 |
| 0.003 | \(8.75 \cdot 10^{-3}\) | 0.0177 | 0.867 | \(7.65 \cdot 10^{-5}\) | \(5.75 \cdot 10^{-5}\) | 1.936 |
| 0.010 | \(9.12 \cdot 10^{-3}\) | 0.0391 | 0.815 | \(8.32 \cdot 10^{-5}\) | \(5.52 \cdot 10^{-5}\) | 1.936 |
| 0.030 | \(1.02 \cdot 10^{-2}\) | 0.1002 | 0.737 | \(1.04 \cdot 10^{-4}\) | \(5.64 \cdot 10^{-5}\) | 1.936 |
| 0.100 | \(1.16 \cdot 10^{-2}\) | 0.3120 | 0.619 | \(1.34 \cdot 10^{-4}\) | \(5.13 \cdot 10^{-5}\) | 1.936 |
| 0.300 | \(1.47 \cdot 10^{-2}\) | 0.9150 | 0.502 | \(2.16 \cdot 10^{-4}\) | \(5.44 \cdot 10^{-5}\) | 1.936 |
| 1.000 | \(1.93 \cdot 10^{-2}\) | 3.0190 | 0.384 | \(3.72 \cdot 10^{-4}\) | \(5.50 \cdot 10^{-5}\) | 1.936 |
As is evident from the data presented in Table 1 and represented graphically in Fig. 1, the solubility of the silver bromate precipitate increases regularly with increasing concentration of zinc nitrate, changing from \(8.43 \cdot 10^{-3}\) for a 0.001 M zinc nitrate solution to \(1.93 \cdot 10^{-2}\) mol/l for a one-molar solution, i.e., it increases by a factor of 2.29.
In accordance with this, the activity coefficient and the solubility product of silver bromate change. With increasing concentration of the foreign electrolyte in this system, the activity coefficient of \(\mathrm{AgBrO_3}\) changes from 0.890 for a 0.001 molar zinc nitrate solution to 0.384 for
of a one-molar solution, i.e., decreases by a factor of 2.32. The solubility product of the precipitate in the ternary system under consideration, as in all the systems studied by us earlier [1, 2, 5, 6], changes markedly with change in the concentration of the foreign electrolyte. If in a 0.001 molar solution of zinc nitrate the value of the solubility product is close to its value in pure water and is equal to \(7.11 \cdot 10^{-5}\), then in a one-molar solution of \(\mathrm{Zn(NO_3)_2}\) it reaches \(3.72 \cdot 10^{-4}\), i.e., increases by a factor of 5.47 compared with the solubility product of the precipitate in water.
Fig. 1. Change in the solubility of \(\mathrm{AgBrO_3}\) in solutions of \(\mathrm{Zn(NO_3)_2}\) and \(\mathrm{Cd(NO_3)_2}\)
Analysis of all the experimental data and the results of the corresponding calculations obtained by us for this system, and comparison of these data with data obtained by us earlier in studying the behavior of the silver bromate precipitate in solutions of magnesium, calcium, strontium, and barium nitrates, show that
Table 2
Solubility of \(\mathrm{AgBrO_3}\) in the system \(\mathrm{AgBrO_3—Cd(NO_3)_2—H_2O}\)
| \(\mathrm{Cd(NO_3)_2}\), mol/l | \(\mathrm{AgBrO_3}\), mol/l | \(\mu\) | \(\gamma\) | \(L_p\) | \(L_a\) | \(a\) |
|---|---|---|---|---|---|---|
| 0.000 | \(8.25 \cdot 10^{-3}\) | 0.0082 | 0.900 | \(6.8 \cdot 10^{-5}\) | \(5.50 \cdot 10^{-5}\) | 2.385 |
| 0.001 | \(8.13 \cdot 10^{-3}\) | 0.0111 | 0.892 | \(6.61 \cdot 10^{-5}\) | \(5.26 \cdot 10^{-5}\) | 2.385 |
| 0.003 | \(8.42 \cdot 10^{-3}\) | 0.0174 | 0.870 | \(7.09 \cdot 10^{-5}\) | \(5.37 \cdot 10^{-5}\) | 2.385 |
| 0.010 | \(8.75 \cdot 10^{-3}\) | 0.0388 | 0.820 | \(7.66 \cdot 10^{-5}\) | \(5.16 \cdot 10^{-5}\) | 2.385 |
| 0.030 | \(9.10 \cdot 10^{-3}\) | 0.0991 | 0.746 | \(8.28 \cdot 10^{-5}\) | \(4.60 \cdot 10^{-5}\) | 2.385 |
| 0.100 | \(1.04 \cdot 10^{-2}\) | 0.3100 | 0.637 | \(1.08 \cdot 10^{-4}\) | \(4.38 \cdot 10^{-5}\) | 2.385 |
| 0.300 | \(1.32 \cdot 10^{-2}\) | 0.9130 | 0.530 | \(1.74 \cdot 10^{-4}\) | \(4.89 \cdot 10^{-5}\) | 2.385 |
| 1.000 | \(1.74 \cdot 10^{-2}\) | 3.0170 | 0.426 | \(3.03 \cdot 10^{-4}\) | \(5.50 \cdot 10^{-5}\) | 2.385 |
the effect of zinc nitrate on the most important characteristics of the silver bromate precipitate in the system
\(\mathrm{AgBrO_3—Zn(NO_3)_2—H_2O}\) is approximately the same as that exerted by the corresponding concentrations of strontium nitrate in the system
\(\mathrm{AgBrO_3—Sr(NO_3)_2—H_2O}\). Table 3 gives all the values obtained by us for
Table 3
Activity coefficients of \(\mathrm{AgBrO_3}\) in aqueous solutions of nitrates of metals of the second group of the periodic system of elements of D. I. Mendeleev
| \(C\) of metal nitrate | \(\gamma \mathrm{AgBrO_3}\) in solutions: \(\mathrm{Zn(NO_3)_2}\) | \(\gamma \mathrm{AgBrO_3}\) in solutions: \(\mathrm{Cd(NO_3)_2}\) | \(\gamma \mathrm{AgBrO_3}\) in solutions: \(\mathrm{Mg(NO_3)_2}\) | \(\gamma \mathrm{AgBrO_3}\) in solutions: \(\mathrm{Ca(NO_3)_2}\) | \(\gamma \mathrm{AgBrO_3}\) in solutions: \(\mathrm{Sr(NO_3)_2}\) | \(\gamma \mathrm{AgBrO_3}\) in solutions: \(\mathrm{Ba(NO_3)_2}\) | Mean value \(\gamma \mathrm{AgBrO_3}\) |
|---|---|---|---|---|---|---|---|
| 0,001 | 0,890 | 0,892 | 0,891 | 0,893 | 0,890 | 0,891 | 0,891 |
| 0,003 | 0,867 | 0,870 | 0,870 | 0,870 | 0,867 | 0,868 | 0,869 |
| 0,010 | 0,815 | 0,820 | 0,820 | 0,818 | 0,815 | 0,816 | 0,817 |
| 0,030 | 0,737 | 0,746 | 0,745 | 0,741 | 0,736 | 0,736 | 0,740 |
| 0,100 | 0,619 | 0,637 | 0,634 | 0,630 | 0,619 | 0,619 | 0,626 |
| 0,300 | 0,502 | 0,530 | 0,532 | 0,519 | 0,500 | 0,498 | 0,513 |
| 1,000 | 0,384 | 0,426 | 0,428 | 0,410 | 0,382 | — | 0,406 |
the activity coefficient of the precipitate in solutions of nitrates of six metals of the second group of the periodic system of elements of D. I. Mendeleev: magnesium, calcium, strontium, barium, zinc, and cadmium. As is evident from the data in this table, over the entire range of concentrations of the external electrolytes studied, the activity coefficients of \(\mathrm{AgBrO_3}\) in the systems
\[ \mathrm{AgBrO_3—Zn(NO_3)_2—H_2O} \quad \text{and} \quad \mathrm{AgBrO_3—Sr(NO_3)_2—H_2O} \]
are approximately identical. Table 4 gives summary data characterizing the behavior of the precipitate in one-molar solutions of zinc, cadmium, magnesium, calcium, and strontium nitrates. As is evident from these data, the solubility of silver broma-
Table 4
Behavior of \(\mathrm{AgBrO_3}\) in molar solutions of \(\mathrm{Me(NO_3)_2}\)
| Electrolyte | \(C\,\mathrm{AgBrO_3}\cdot 10^2\) | \(L'_p : L_p\)¹ | \(L'_i : L_i\)² | \(a\) |
|---|---|---|---|---|
| \(\mathrm{Zn(NO_3)_2}\) | 1,93 | 5,47 | 2,34 | 1,94 |
| \(\mathrm{Cd(NO_3)_2}\) | 1,74 | 4,45 | 2,11 | 2,39 |
| \(\mathrm{Mg(NO_3)_2}\) | 1,73 | 4,41 | 2,10 | 2,41 |
| \(\mathrm{Ca(NO_3)_2}\) | 1,81 | 4,80 | 2,19 | 2,19 |
| \(\mathrm{Sr(NO_3)_2}\) | 1,94 | 5,50 | 2,35 | 1,91 |
1) \(L'_p\) and \(L_p\)—the solubility product of \(\mathrm{AgBrO_3}\), respectively, in a one-molar nitrate solution and in water.
2) \(L'_i\) and \(L_i\)—the solubility of \(\mathrm{AgBrO_3}\), respectively, in a one-molar nitrate solution and in water.
than in a one-molar solution of zinc nitrate increases by a factor of 2.34 in comparison with its solubility in water, and in a one-molar solution of strontium nitrate—by a factor of 2.35. The solubility product of the precipitate in a one-molar solution of zinc nitrate is 5.47 times greater than in water, and in a one-molar solution of strontium nitrate—5.50 times. The value of the coefficient \(\alpha\) in this variant of the Debye and Hückel formula, which we used to calculate the activity coefficient of the precipitate by the method developed by I. V. Tananaev and I. B. Mizenko [7], is equal to 1.94 in the system AgBrO\(_3\)—Zn(NO\(_3\))\(_2\)—H\(_2\)O, and to 1.91 in the system AgBrO\(_3\)—Sr(NO\(_3\))\(_2\)—H\(_2\)O.
Thus, the cation of the metal zinc, i.e., an element of the odd subgroup of the second group of elements of the periodic system, located in the fourth period, in the ternary system studied by us exerts approximately the same influence on the behavior of the precipitate as is exerted by the cation of strontium—an element of the even subgroup of the second group and of the fifth period of D. I. Mendeleev’s periodic system of elements. In this connection, all the conclusions previously drawn by us for the system AgBrO\(_3\)—Sr(NO\(_3\))\(_2\)—H\(_2\)O are, in the main, also valid for the ternary system AgBrO\(_3\)—Zn(NO\(_3\))\(_2\)—H\(_2\)O.
System AgBrO\(_3\)—Cd(NO\(_3\))\(_2\)—H\(_2\)O
The experimental data obtained by us for the system silver bromate—cadmium nitrate—water, and the results of the corresponding calculations for this system, are given in Table 2 and are represented graphically in Figs. 1 and 2. From these data it is evident that the solubility of silver bromate in the ternary system under consideration
Fig. 2. Change in the solubility product in solutions of Zn(NO\(_3\))\(_2\) and Cd(NO\(_3\))\(_2\)
regularly increases with increasing concentration of the external electrolyte. This fact, first of all, indicates the absence in this system of any obvious chemical interaction between the external electrolyte and silver bromate.
At low concentrations of cadmium nitrate, the solubility of the precipitate differs little from its solubility in water at the same temperature.
However, already in a centimolar solution the solubility of the precipitate increases by more than 6%, and in a one-molar solution the solubility reaches \(1.74 \cdot 10^{-2}\) mole/l, i.e., it increases by a factor of 2.11 compared with its solubility in water.
In accordance with the change in the solubility of the precipitate, with increasing concentration of the foreign electrolyte there occurs a regular decrease in the activity coefficient and an increase in the solubility product of silver bromate. In a one-molar solution of cadmium nitrate the solubility product of the precipitate becomes equal to \(3.03 \cdot 10^{-4}\), i.e., in the concentration range of the foreign electrolyte under consideration it increases by a factor of 4.45.
In Figs. 1, 2, and 3 and in Tables 3, 4, and 5, the principal data for this system are compared with the corresponding data for the silver bromate–zinc nitrate–water system and with data for systems studied earlier by us, in which magnesium, calcium, strontium, and barium nitrates were taken as electrolytes [1].
Table 5
Change in the solubility and solubility product of \(\mathrm{AgBrO_3}\) in aqueous solutions of \(\mathrm{Zn(NO_3)_2}\) and \(\mathrm{Cd(NO_3)_2}\)
| \(C\) nitrate, mole/l | \(\lg C\) | \(\mathrm{Zn(NO_3)_2}\): \(C_{\mathrm{AgBrO_3}}\cdot 10^3\) | \(\mathrm{Zn(NO_3)_2}\): \(L_p \cdot 10^5\) | \(\mathrm{Zn(NO_3)_2}\): \(\lg L_p\) | \(\mathrm{Cd(NO_3)_2}\): \(C_{\mathrm{AgBrO_3}}\cdot 10^3\) | \(\mathrm{Cd(NO_3)_2}\): \(L_p \cdot 10^5\) | \(\mathrm{Cd(NO_3)_2}\): \(\lg L_p\) |
|---|---|---|---|---|---|---|---|
| 0.001 | −3.0 | 8.43 | 7.11 | −4.15 | 8.13 | 6.61 | −4.18 |
| 0.003 | −2.5 | 8.75 | 7.65 | −4.12 | 8.42 | 7.09 | −4.15 |
| 0.010 | −2.0 | 9.12 | 8.32 | −4.08 | 8.75 | 7.66 | −4.11 |
| 0.030 | −1.5 | 10.20 | 10.40 | −3.98 | 9.10 | 8.28 | −4.08 |
| 0.100 | −1.0 | 11.60 | 13.40 | −3.87 | 10.40 | 10.80 | −3.97 |
| 0.300 | −0.5 | 14.70 | 21.60 | −3.66 | 13.20 | 17.40 | −3.76 |
| 1.000 | 0.0 | 19.30 | 37.20 | −3.43 | 17.40 | 30.30 | −3.52 |
In all the ternary systems previously studied by us, where nitrates of metals of the main subgroups of the corresponding groups of elements of the periodic system were taken as the foreign electrolytes, the greatest increase in the solubility and in the solubility product of the precipitate was produced by cations with the largest ionic radii and atomic weights. However, this indisputable fact, established by us for ternary systems in which the foreign electrolytes were magnesium, calcium, strontium, and barium nitrates, and confirmed with sufficient conviction by experimental data obtained by us in studying solubility in ternary systems with the foreign electrolytes \(\mathrm{LiNO_3}\), \(\mathrm{NaNO_3}\), and \(\mathrm{KNO_3}\) [2], does not hold for the silver bromate–zinc nitrate–water and silver bromate–cadmium nitrate–water systems. As is seen from the data of Tables 4 and 5 and Figs. 1, 2, and 4, the zinc cation—an element of the fourth period of the periodic system of elements, characterized by an atomic weight of 65.38 and an ionic radius according to Goldschmidt of 0.83 Å [8]—affects the behavior of the silver bromate precipitate to a significantly greater extent than the cadmium cation, although the latter is an element of the fifth period and is characterized by an atomic weight of 112.41 and an ionic radius of 1.03 Å. If in a one-molar solution of zinc nitrate the solubility of the silver bromate precipitate increases by a factor of 2.34 compared with its solubility in water, then in a one-molar solution of cadmium nitrate it increases only by a factor of 2.11. If the solubility product of the precipitate in a molar solution of zinc nitrate increases by a factor of 5.47, then in a one-molar solution of cadmium nitrate it increases only by a factor of 4.45. If the activity coefficient of silver bromate in the concentration range under consideration
concentrations of zinc nitrate decreases to 0.384, whereas in the corresponding cadmium nitrate solutions it decreases only to 0.426. Thus, in the ternary systems considered here, the conclusion is confirmed that, when evaluating the influence of external electrolytes on the solubility of a given precipitate, it is necessary to take into account all the individual chemical features of the corresponding electrolytes and of the ions formed by them in solution. However, a more or less complete account of these features is possible only after sufficient experimental material has been accumulated on the physicochemical study of the solubility of precipitates of various types in solutions of different electrolytes.
Fig. 3. Mean value of the activity coefficient as a function of the concentration of the external electrolyte.
Fig. 4. Dependence of the solubility of AgBrO\(_3\) on the ionic strength of Zn(NO\(_3\))\(_2\) and Cd(NO\(_3\))\(_2\) solutions.
In evaluating the experimental data obtained by us for the ternary system AgBrO\(_3\)—Cd(NO\(_3\))\(_2\)—H\(_2\)O, it should be especially noted that, by all the most important indices characterizing the influence of the concentration of cadmium ions on the behavior of the silver bromate precipitate, the system under consideration is very close to the system AgBrO\(_3\)—Mg(NO\(_3\))\(_2\)—H\(_2\)O. As is seen from the data of Tables 3 and 4, over the entire concentration range of these two external electrolytes the activity coefficients of AgBrO\(_3\) practically coincide. The ratio of the solubility of the precipitate in a one-molar cadmium nitrate solution to its solubility in water is 2.11, while in a one-molar magnesium nitrate solution it is 2.10. The increase in the solubility product in a one-molar cadmium nitrate solution, as compared with water, is characterized by the figure 4.45, and in a one-molar magnesium nitrate solution by 4.41. The ionic strengths of the solutions in these two ternary systems are also close to one another. Thus, the cadmium cation in the ternary system AgBrO\(_3\)—Cd(NO\(_3\))\(_2\)—H\(_2\)O has practically the same influence on the solubility of the precipitate as the magnesium cation has in the system AgBrO\(_3\)—Mg(NO\(_3\))\(_2\)—H\(_2\)O.
An analysis of the data available in the literature characterizing the properties of the nitrates of metals of the second group of D. I. Mendeleev’s periodic system shows that, in certain other properties as well, cadmium nitrate is very
close to magnesium nitrate. Thus, for example, the equivalent electrical conductivity of a 0.01 N solution of magnesium nitrate at 18°C is 94.7, that of cadmium nitrate is 96.0 ohm\(^{-1}\) cm\(^2\)/g-equiv. The equivalent electrical conductivities of 0.1 N solutions of magnesium and cadmium nitrates are, respectively, 80.5 and 80.8 ohm\(^{-1}\) cm\(^2\)/g-equiv [9].
The equivalent electrical conductivity of nitrates of all other metals of the second group of the periodic system, under equal conditions, differs appreciably from these data.
In our previously published communication on the solubility of silver bromate in aqueous solutions of magnesium, calcium, strontium, and barium nitrates [1], it was shown that the calculation of the solubility of AgBrO\(_3\) in aqueous solutions of alkaline-earth metal nitrates in the concentration range from 0.001 to 1 mol/l at 25° can, with accuracy sufficient for practical purposes, be carried out by the formula
\[ C_{\mathrm{AgBrO_3}}=\sqrt{\frac{L_a}{\gamma^2}}, \]
where \(L_a\) is the activity product of AgBrO\(_3\), found by us to be equal to \(5.50 \cdot 10^{-5}\); \(\gamma\) is the mean activity coefficient of AgBrO\(_3\) in aqueous solutions of magnesium, calcium, strontium, and barium nitrates, determined from the curve of the dependence of the mean activity coefficient on the concentration of the external electrolyte.
As is seen from Table 3 and Fig. 3, the mean activity coefficients of silver bromate practically do not change if, in determining them, the behavior of the precipitate in aqueous solutions of zinc and cadmium nitrates is also taken into account. This fact gives us the right to extend the above recommendation also to aqueous solutions of zinc and cadmium nitrates at concentrations of the latter from 0.001 to 1 mol/l.
Conclusions
The solubility of a silver bromate precipitate in aqueous solutions of zinc and cadmium nitrates was investigated at external-electrolyte concentrations from 0.001 to 1 mol/l at 25°C.
It was established that the solubility and the solubility product of AgBrO\(_3\) precipitate in these systems increase regularly with increasing concentration of the external electrolytes.
The experimental data for these systems were used to determine the activity coefficients of silver bromate in aqueous solutions of zinc and cadmium nitrates.
The extent of change in the solubility product of silver bromate precipitate in aqueous solutions of zinc and cadmium nitrates as a function of the ionic strength of the solutions is shown.
It is demonstrated that zinc nitrate has approximately the same effect on the behavior of AgBrO\(_3\) precipitate as strontium nitrate has in the system AgBrO\(_3\)—Sr(NO\(_3\))\(_2\)—H\(_2\)O, while cadmium nitrate has approximately the same effect as magnesium nitrate has in the system AgBrO\(_3\)—Mg(NO\(_3\))\(_2\)—H\(_2\)O.
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