Study of the Solubility of Silver Bromate Precipitate in Aqueous Solutions of Aluminum and Thorium Nitrates
Abstract Generated abstract
The study examines how aluminum and thorium nitrates affect the solubility of silver bromate in water at 25 °C over electrolyte concentrations from 0.001 to 1 mol/l. Using gravimetric determination of dissolved silver and calculations based on a Debye-Hückel treatment, the work determines solubilities, activity coefficients, solubility products, and activity products for the two ternary systems. Silver bromate solubility increases with nitrate concentration, reaching about 2.22 times its water solubility in 1 M aluminum nitrate and 2.70 times in 1 M thorium nitrate, while activity coefficients decrease markedly. Comparison with earlier sodium and magnesium nitrate data suggests that at equal normality sodium nitrate produces the greatest increase in solubility among sodium, magnesium, and aluminum nitrates, and aluminum nitrate the smallest.
Full Text
STUDY OF THE SOLUBILITY OF SILVER BROMATE PRECIPITATE IN AQUEOUS SOLUTIONS OF ALUMINUM AND THORIUM NITRATES
Yu. L. Del’chuk
The present study is a continuation of work carried out and published by us on the solubility of silver bromate in aqueous solutions of various salts.
In the first two of our communications, we considered the results of a study of the effect of nitrates of the alkali metals lithium, sodium, and potassium [1], and of the metals of the second group of D. I. Mendeleev’s periodic system—barium, strontium, calcium, and magnesium [2]—on the solubility of silver bromate at 25° at concentrations of the external electrolytes from 0.001 to 1 mol/l. In these two studies we established that the solubility of silver bromate precipitate in aqueous solutions of nitrates of alkali and alkaline-earth metals depends not only on the valence type of the external electrolyte, but also depends significantly on the position of the corresponding element in the first or second groups of D. I. Mendeleev’s periodic system. Both in aqueous solutions of nitrates of the alkali metals lithium, sodium, and potassium, and in aqueous solutions of nitrates of the metals of the second group of the periodic system—magnesium, calcium, strontium, and barium—the solubility of silver bromate increases regularly with increasing atomic weight and atomic radius of the corresponding metals. This regularity, barely noticeable at low concentrations of the external electrolytes, becomes very pronounced already at concentrations of the corresponding nitrates of 0.01 mol/l and higher. In accordance with the change in solubility, the solubility product of the precipitate also changes significantly with the change in concentration of the external electrolytes.
As a result of these studies, we determined the activity coefficients, the solubility product, and the activity product of silver bromate, and also showed the scale of the change in the solubility product of this precipitate in nitrate solutions of alkali and alkaline-earth metals of various concentrations; we proposed a formula for calculating, with accuracy sufficient for practical purposes, the solubility of silver bromate in aqueous solutions of nitrates of the alkali metals lithium, sodium, and potassium and of the metals of the second group of D. I. Mendeleev’s periodic system—magnesium, calcium, strontium, and barium—at concentrations of the external electrolytes from 0.001 to 1 mol/l.
The present communication is devoted to the results of a study of the solubility of silver bromate in aqueous solutions of aluminum and thorium nitrates. The experimental data obtained in studying solubility in the system $\mathrm{AgBrO_3}—\mathrm{Al(NO_3)_3}—\mathrm{H_2O}$ are compared with data obtained by us earlier for the systems $\mathrm{AgBrO_3}—\mathrm{Mg(NO_3)_2}—\mathrm{H_2O}$ [2] and $\mathrm{AgBrO_3}—\mathrm{NaNO_3}—\mathrm{H_2O}$ [1], for the purpose of a comparative assessment of the influence of the cations of the first three elements of the third period of the periodic system on the solubility of silver bromate precipitate.
The purpose of the present work is to study the effect of the concentration of aluminum and thorium nitrates on the solubility of a silver bromate precipitate, to determine the activity coefficients of silver bromate in these solutions, to establish the scale of variation of the solubility product of the precipitate as a function of the concentration of electrolytes with polyvalent cations, and to reveal the general regularities in the influence of the corresponding cations on the solubility of the precipitate as a function of the position of the chemical element in the corresponding period of D. I. Mendeleev’s periodic system.
In order to reveal as fully as possible the relative influence of aluminum and thorium nitrates and to make it possible to compare the experimental data for these two systems with the data obtained by us earlier for magnesium, calcium, strontium, barium, lithium, sodium, and potassium nitrates, we fully retained the research procedure and the range of concentrations of the external electrolytes used in the previous studies of bromate systems.
In the future it is intended to study the solubility of silver bromate in aqueous and aqueous-alcoholic solutions of salts of many other metals. The solubility studies will be carried out both in ternary and in quaternary systems, which are of great practical importance in analytical chemistry. As components, along with salts having no ions in common with the precipitate, salts of $\mathrm{KBrO_3}$ and $\mathrm{AgNO_3}$ will also be taken. Certain experimental material on these systems has already been collected by the author jointly with members of the Department of General Inorganic Chemistry of TPI, L. V. Surnina and V. I. Barkhatova.
Starting Materials and Experimental Procedure
Thorium nitrate, corresponding to the formula $\mathrm{Th(NO_3)_4 \cdot 4H_2O}$, was obtained by us from commercial thorium sulfate by the method proposed by Koppel and Holtkamp [3]. Ammonia was added to thorium sulfate until complete precipitation. The solution together with the precipitate was boiled for 10–15 minutes, filtered by suction on a Büchner funnel, and washed with water until a negative reaction for sulfate ion was obtained. After this the precipitate was treated with concentrated nitric acid and evaporated to dryness on a water bath.
Aluminum nitrate was obtained by us by threefold recrystallization of a domestic commercial preparation $\mathrm{Al(NO_3)_3 \cdot 9H_2O}$. After suction filtration, the crystals of aluminum nitrate were dried on filter paper.
Silver bromate was obtained by adding to a 10-percent solution of chemically pure silver nitrate, dropwise in the cold and with continuous motor stirring, an equivalent amount of a 5-percent solution of chemically pure potassium bromate. The precipitate was washed repeatedly with bidistilled water and pressed on filter paper to an air-dry state. The resulting preparation was stored in a brown-glass jar, additionally protected from the action of light by a cover of thick black paper.
All solutions of aluminum and thorium nitrate were prepared by appropriate dilution of one-molar solutions of these salts with bidistillate. The concentrations of the stock solutions were determined gravimetrically, aluminum being determined as $\mathrm{Al_2O_3}$ and thorium as $\mathrm{ThO_2}$.
Experiments to determine the solubility of the silver bromate precipitate in the systems $\mathrm{AgBrO_3 — Al(NO_3)_3 — H_2O}$ and $\mathrm{AgBrO_3 — Th(NO_3)_4 — H_2O}$ were carried out in brown-glass flasks, paraffined on the inside, with a capacity of 400–500 ml. A flask closed with a cork stopper, containing 1 g $\mathrm{AgBrO_3}$ and 250 ml of aluminum or thorium nitrate solution of a given concentration, was placed in a water thermostat at a temperature of $25^\circ \pm 0.1^\circ$, where vigorous motor stirring was carried out for 8 hours. The temperature
in the thermostat was maintained with the aid of a mercury–toluene thermoregulator. Before a sample was taken for determining the solubility of silver bromate, the solution with the precipitate was allowed to stand in the thermostat for 45–60 min. The concentration of AgBrO₃ in all the solutions we studied was determined from the content of silver ions. Silver was determined gravimetrically in the form of silver chloride and, in individual cases, additionally in the form of silver bromide, which was obtained by reduction of silver bromate in the liquid phase with potassium nitrite in nitric acid medium. Precipitation of the precipitates and their settling were carried out in beakers protected from the action of light by caps made of black paper. Filtration and drying of the gravimetric form were carried out in glass crucibles with a filtering bottom No. 3. For each point of the systems we studied, two parallel experiments were performed, and in each liquid phase the content of AgBrO₃ was determined in two parallel samples. For determining the solubility of silver bromate and calculating the solubility product, the ionic strength of the solutions, the activity coefficients, and the activity product of AgBrO₃, the arithmetic mean values of these determinations were used.
All calculations for the systems studied were carried out by the method developed by I. V. Tanaev and I. B. Mazetskaya [4] and successfully applied by them in studying the solubility of a lead sulfate precipitate in solutions of electrolytes of various types [5, 6]. This scheme is examined in detail in our communication on the solubility of a silver bromate precipitate in aqueous solutions of the nitrates of the alkali metals lithium, sodium, and potassium [2].
System AgBrO₃—Al(NO₃)₃—H₂O
The results of determining the solubility of AgBrO₃ in aqueous solutions of aluminum nitrate and of calculating the ionic strength of the solutions, the activity coefficients, the solubility products, and the activity product of silver bromate are given in Table 1 and in Fig. 1. In the first column of the table the concentrations of aluminum nitrate are indicated; in the second, the molarity of AgBrO₃ in the saturated solution; in the third, the ionic strengths of the solutions; in the fourth, the activity coefficients of AgBrO₃; 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 the external electrolytes exceeding the Debye region.
Table 1
Solubility of AgBrO₃ in the system
AgBrO₃—Al(NO₃)₃—H₂O
| Al(NO₃)₃, mol/l | AgBrO₃, mol/l | μ | γ | Lp | La | a |
|---|---|---|---|---|---|---|
| 0.000 | \(8.25 \cdot 10^{-3}\) | 0.0082 | 0.900 | \(6.80 \cdot 10^{-5}\) | \(5.50 \cdot 10^{-5}\) | |
| 0.001 | \(8.34 \cdot 10^{-3}\) | 0.0143 | 0.881 | \(6.95 \cdot 10^{-5}\) | \(5.39 \cdot 10^{-5}\) | |
| 0.003 | \(8.70 \cdot 10^{-3}\) | 0.0267 | 0.847 | \(7.57 \cdot 10^{-5}\) | \(5.43 \cdot 10^{-5}\) | |
| 0.010 | \(9.26 \cdot 10^{-3}\) | 0.0693 | 0.780 | \(8.57 \cdot 10^{-5}\) | \(5.21 \cdot 10^{-5}\) | |
| 0.030 | \(1.01 \cdot 10^{-2}\) | 0.1900 | 0.693 | \(1.02 \cdot 10^{-4}\) | \(4.90 \cdot 10^{-5}\) | 2.664 |
| 0.100 | \(1.15 \cdot 10^{-2}\) | 0.6110 | 0.584 | \(1.32 \cdot 10^{-4}\) | \(4.49 \cdot 10^{-5}\) | |
| 0.300 | \(1.38 \cdot 10^{-2}\) | 1.8140 | 0.488 | \(1.90 \cdot 10^{-4}\) | \(4.52 \cdot 10^{-5}\) | |
| 1.000 | \(1.83 \cdot 10^{-2}\) | 6.0180 | 0.405 | \(3.35 \cdot 10^{-4}\) | \(5.50 \cdot 10^{-5}\) |
As is seen from the data presented in Table 1 and graphically depicted in Fig. 1, the solubility of the silver bromate precipitate increases regularly with increasing concentration of aluminum nitrate, from \(8.34 \cdot 10^{-3}\) mol/l for a 0.001 M solution to \(1.83 \cdot 10^{-2}\) for a one-molar solution of Al(NO₃)₃, i.e., by a factor of 2.2. The activity coefficients, as was to be expected,
regularly decrease with increasing concentration of the foreign electrolyte and fall to 0.405 for a one-molar solution of Al(NO₃)₃.
The activity product of AgBrO₃ for all the Al(NO₃)₃ concentrations we studied, in the range from 0.001 M to 1 mole/l, is practically a constant quantity, and only for individual concentrations does this value deviate insignificantly from the value previously found by us, \(5.5 \cdot 10^{-5}\).
In this system, as also in the systems previously studied by us, the solubility product of the AgBrO₃ precipitate increases considerably with increasing concentration of aluminum nitrate, changing from \(6.95 \cdot 10^{-5}\) for a 0.001 M solution to \(3.35 \cdot 10^{-4}\) for a one-molar solution of Al(NO₃)₃, i.e., almost fivefold.
Of particular interest is a comparison of the data obtained for the system AgBrO₃—Al(NO₃)₃—H₂O with the data obtained by us earlier for the systems AgBrO₃—Mg(NO₃)₂—H₂O [2] and AgBrO₃—NaNO₃—H₂O [1], since sodium, magnesium, and aluminum are elements arranged in the order of increasing atomic weights and positive nuclear charges of the atoms in the third period of D. I. Mendeleev’s periodic system of elements.
Fig. 1. Solubility of AgBrO₃ in aqueous solutions of Al(NO₃)₃
Analysis of the experimental data obtained by us in studying the solubility in these three systems makes it possible to draw some preliminary conclusions regarding the degree of influence of the corresponding cations on the solubility of the precipitate, depending on the position occupied by a given element in the given period of the periodic system of elements, since in all these three systems the second ion of the foreign salt is one and the same—the nitrate ion.
The principal data for these three systems are given in Tables 2, 3, and 4 and in Figs. 2, 3, and 4. In all three systems, the solubility and the solubility product of the precipitate increase considerably with increasing concentration of the foreign electrolyte. However, the degree of increase in the solubility of the precipitate with increasing concentration of the foreign electrolyte is also noticeably influenced by the valence of the cation and the position occupied by the element in the corresponding period of the periodic system.
Table 2
Change in the solubility and solubility product of AgBrO₃ in solutions of NaNO₃, Mg(NO₃)₂, and Al(NO₃)₃.
| Nitrate concentration, mol/L | log C | NaNO₃: CAgBrO₃ · 10³ | NaNO₃: Lp · 10⁶ | Mg(NO₃)₂: CAgBrO₃ · 10³ | Mg(NO₃)₂: Lp · 10⁶ | Al(NO₃)₃: CAgBrO₃ · 10³ | Al(NO₃)₃: Lp · 10⁶ |
|---|---|---|---|---|---|---|---|
| 0.001 | −3.0 | 8.22 | 6.76 | 8.56 | 7.33 | 8.34 | 6.95 |
| 0.003 | −2.5 | 8.31 | 6.91 | 8.72 | 7.60 | 8.70 | 7.57 |
| 0.010 | −2.0 | 8.50 | 7.23 | 9.28 | 8.61 | 9.26 | 8.57 |
| 0.030 | −1.5 | 9.27 | 8.59 | 9.81 | 9.62 | 10.10 | 10.20 |
| 0.100 | −1.0 | 10.08 | 10.20 | 11.10 | 12.30 | 11.50 | 13.20 |
| 0.300 | −0.5 | 11.38 | 13.00 | 12.70 | 16.10 | 13.80 | 19.00 |
| 1.000 | 0.0 | 14.80 | 21.90 | 17.30 | 30.00 | 18.30 | 33.59 |
Table 3
Activity coefficients of AgBrO₃ in solutions of NaNO₃, Mg(NO₃)₂, and Al(NO₃)₃
| Nitrate concentration, mol/L | γAgBrO₃ in NaNO₃ solutions | γAgBrO₃ in Mg(NO₃)₂ solutions | γAgBrO₃ in Al(NO₃)₃ solutions |
|---|---|---|---|
| 0.001 | 0.901 | 0.891 | 0.881 |
| 0.003 | 0.891 | 0.870 | 0.847 |
| 0.010 | 0.865 | 0.820 | 0.780 |
| 0.030 | 0.817 | 0.746 | 0.693 |
| 0.100 | 0.730 | 0.634 | 0.583 |
| 0.300 | 0.626 | 0.532 | 0.488 |
| 1.000 | 0.501 | 0.428 | 0.405 |
Table 4
Behavior of AgBrO₃ in molar solutions of NaNO₃, Mg(NO₃)₂, and Al(NO₃)₃
| Electrolyte | CAgBrO₃ · 10² | L′p : Lp¹) | L′i : Li²) | α |
|---|---|---|---|---|
| NaNO₃ | 1.48 | 3.22 | 1.79 | 2.090 |
| Mg(NO₃)₂ | 1.73 | 4.37 | 2.10 | 2.410 |
| Al(NO₃)₃ | 1.83 | 4.93 | 2.22 | 2.664 |
¹) L′p and Lp are the solubility products of AgBrO₃, respectively, in a one-molar nitrate solution and in water.
²) L′i and Li are the solubilities of AgBrO₃, respectively, in a one-molar nitrate solution and in water.
Of all the ternary systems considered, the greatest increase in the solubility of AgBrO₃ is produced by aluminum nitrate, and the smallest by sodium nitrate. In a molar solution of sodium nitrate, the solubility of AgBrO₃ increases by a factor of 1.79 in comparison with its solubility in water; in a molar solution of magnesium nitrate, by a factor of 2.10; and in a molar solution of aluminum nitrate, by a factor of 2.22. In accordance with the change in solubility, the solubility product also changes. In a molar solution of sodium nitrate, the solubility product of AgBrO₃ is 3.22 times greater than the solubility product of this precipitate in water; in a molar solution of magnesium nitrate, 4.37 times greater; and in a molar solution of aluminum nitrate, 4.93 times greater. However, it is easy to see that the increase in solubility and in the product
the solubility of the precipitate appreciably lags behind the increase in the valence of the corresponding cation. This is clearly seen from a comparative assessment of the solubility data for \(\mathrm{AgBrO_3}\) in nitrate solutions of equal normality. In one-normal solutions of \(\mathrm{NaNO_3}\), \(\mathrm{Mg(NO_3)_2}\), and \(\mathrm{Al(NO_3)_3}\), the solubility of silver bromate is respectively equal to \(1.48 \cdot 10^{-2}\), \(1.40 \cdot 10^{-2}\), and \(1.38 \cdot 10^{-2}\ \mathrm{mol/l}\). The solubility product of the precipitate changes correspondingly. If in a one-normal solution of \(\mathrm{NaNO_3}\) the solubility product of \(\mathrm{AgBrO_3}\) is 3.22 times greater than the solubility product of this precipitate in pure water, then in a one-normal solution of \(\mathrm{Al(NO_3)_3}\) it is only 2.8 times greater.
Fig. 2. Solubility of \(\mathrm{AgBrO_3}\) in aqueous \(\mathrm{NaNO_3}\) solutions
Fig. 3. Change in the solubility of \(\mathrm{AgBrO_3}\) in aqueous solutions of \(\mathrm{NaNO_3}\), \(\mathrm{Mg(NO_3)_2}\), and \(\mathrm{Al(NO_3)_3}\)
The above data show with sufficient persuasiveness how inadequate, in estimating the influence of external electrolytes on the solubility of a given precipitate, is the consideration only of the valence type of the cation, on which Debye and Hückel place special emphasis in their conclusions. The results of our investigations emphasize the necessity of taking into account the individual chemical characteristics of each cation separately. Naturally, a full account of these characteristics will become 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.
System \(\mathrm{AgBrO_3}\)—\(\mathrm{Th(NO_3)_4}\)—\(\mathrm{H_2O}\)
The experimental data obtained by us for the system \(\mathrm{AgBrO_3}\)—\(\mathrm{Th(NO_3)_4}\)—\(\mathrm{H_2O}\) and the results of the corresponding calculations are presented in Table 5 and in Fig. 5. The strictly regular increase in the solubility of the precipitate with increasing concentration of thorium nitrate indicates the absence, in this system as well, of any clearly expressed chemical interaction between the components. As should have been expected, in this system, where the external electrolyte is the nitrate of a tetravalent cation, the increase in solubility and the increase in the solubility product of the precip-
Table 5
Solubility of AgBrO₃ in the system AgBrO₃—Th(NO₃)₄—H₂O
| Th(NO₃)₄, mol/L | AgBrO₃, mol/L | μ | γ | Lₚ | Lₐ | a |
|---|---|---|---|---|---|---|
| 0.000 | 8.25 · 10⁻³ | 0.0082 | 0.900 | 6.80 · 10⁻⁵ | 5.50 · 10⁻⁵ | 2.245 |
| 0.001 | 8.37 · 10⁻³ | 0.0184 | 0.866 | 7.01 · 10⁻⁵ | 5.26 · 10⁻⁵ | 2.245 |
| 0.003 | 8.68 · 10⁻³ | 0.0387 | 0.819 | 7.53 · 10⁻⁵ | 5.05 · 10⁻⁵ | 2.245 |
| 0.010 | 1.02 · 10⁻² | 0.1100 | 0.734 | 1.04 · 10⁻⁴ | 5.59 · 10⁻⁵ | 2.245 |
| 0.030 | 1.12 · 10⁻² | 0.2610 | 0.650 | 1.25 · 10⁻⁴ | 5.29 · 10⁻⁵ | 2.245 |
| 0.100 | 1.35 · 10⁻² | 1.0140 | 0.511 | 1.82 · 10⁻⁴ | 4.75 · 10⁻⁵ | 2.245 |
| 0.300 | 1.59 · 10⁻² | 3.0160 | 0.413 | 2.53 · 10⁻⁴ | 4.33 · 10⁻⁵ | 2.245 |
| 1.000 | 2.23 · 10⁻² | 10.0220 | 0.333 | 4.97 · 10⁻⁴ | 5.50 · 10⁻⁵ | 2.245 |
also, as the concentration of thorium nitrate increases, it proceeds more sharply than in all the other systems previously studied by us, where the valence of the cations of the external electrolytes did not exceed three. The solubility of AgBrO₃ in a one-molar solution of thorium nitrate is 2.23 · 10⁻², which is 2.7 times greater than the solubility of silver bromate in pure water. To an even greater
Fig. 4. Change in the solubility product of AgBrO₃ in solutions of NaNO₃, Mg(NO₃)₂, and Al(NO₃)₃.
Fig. 5. Solubility of AgBrO₃ in aqueous solutions of Th(NO₃)₄.
extent, an increase in the solubility product of the precipitate occurs. In a one-molar solution of thorium nitrate, the solubility product of silver bromate is 7.31 times greater than in water. However, here too, if one compares the effect of solutions of the corresponding nitrates of equal normality on the solubility of the silver bromate precipitate, it is easy to note that nitrates of the alkali metals exert the greatest influence. This fact has already been interpreted by us in the comparative evaluation of data for the systems AgBrO₃—NaNO₃—H₂O, AgBrO₃—Mg(NO₃)₂—H₂O, and AgBrO₃—Al(NO₃)₃—H₂O.
In the system AgBrO₃—Th(NO₃)₄—H₂O, more sharply than in all the other systems previously studied by us, there is also a decrease in the activity coefficient of AgBrO₃, reaching a minimum value of 0.333 in a one-molar solution of thorium nitrate.
It should also be noted that the activity product of silver bromate in this system is likewise not a constant quantity in the strict sense of the word. As in the systems studied previously, the greatest deviation from a constant value is obtained at thorium nitrate concentrations of 0.1 and 0.3 mole/liter, where the activity product of silver bromate is, respectively, equal to \(4.75 \cdot 10^{-5}\) and \(4.33 \cdot 10^{-5}\). This fact, connected, in our opinion, with the imperfection of the second version of the Debye–Hückel formula, by which we determined the activity coefficients of \(\mathrm{AgBrO_3}\), and of our
Fig. 6. Change in the solubility product of \(\mathrm{AgBrO_3}\) in solutions of \(\mathrm{Al(NO_3)_3}\) and \(\mathrm{Th(NO_3)_4}\).
calculation scheme, was considered by us in more detail in a communication on the solubility of silver bromate in aqueous solutions of alkaline-earth metals [2].
In Tables 6, 7, and 8 and Fig. 6, the principal data for the system \(\mathrm{AgBrO_3—Th(NO_3)_4—H_2O}\) are compared with the data for the system \(\mathrm{AgBrO_3—Al(NO_3)_3—H_2O}\).
Table 6
Change in the solubility product of \(\mathrm{AgBrO_3}\) in solutions of \(\mathrm{Al(NO_3)_3}\) and \(\mathrm{Th(NO_3)_4}\)
| \(C\) of nitrate, mole/liter | \(\log C\) | \(\mathrm{Al(NO_3)_3}\): \(L_p \cdot 10^5\) | \(\mathrm{Al(NO_3)_3}\): \(\log L_p\) | \(\mathrm{Th(NO_3)_4}\): \(L_p \cdot 10^5\) | \(\mathrm{Th(NO_3)_4}\): \(\lg L_p\) |
|---|---|---|---|---|---|
| \(1 \cdot 10^{-3}\) | \(-3.0\) | 6.95 | \(-4.16\) | 7.01 | \(-4.15\) |
| \(3 \cdot 10^{-3}\) | \(-2.5\) | 7.57 | \(-4.12\) | 7.53 | \(-4.12\) |
| \(1 \cdot 10^{-2}\) | \(-2.0\) | 8.57 | \(-4.07\) | 10.40 | \(-3.98\) |
| \(3 \cdot 10^{-2}\) | \(-1.5\) | 10.20 | \(-3.99\) | 12.50 | \(-3.90\) |
| \(1 \cdot 10^{-1}\) | \(-1.0\) | 13.20 | \(-3.88\) | 18.20 | \(-3.74\) |
| \(3 \cdot 10^{-1}\) | \(-0.5\) | 19.00 | \(-3.72\) | 25.30 | \(-3.60\) |
| 1.000 | 0.0 | 33.50 | \(-3.47\) | 49.70 | \(-3.30\) |
Table 7
Change in the activity coefficient of AgBrO₃
in solutions of Al(NO₃)₃ and Th(NO₃)₄
| C of nitrate, mol/l | \(\gamma_{\mathrm{AgBrO_3}}\) in Al(NO₃)₃ solutions | \(\gamma_{\mathrm{AgBrO_3}}\) in Th(NO₃)₄ solutions |
|---|---|---|
| 0.000 | 0.900 | 0.900 |
| 0.001 | 0.881 | 0.866 |
| 0.003 | 0.847 | 0.819 |
| 0.010 | 0.780 | 0.734 |
| 0.030 | 0.693 | 0.650 |
| 0.100 | 0.583 | 0.511 |
| 0.300 | 0.488 | 0.413 |
| 1.000 | 0.405 | 0.333 |
Table 8
Behavior of AgBrO₃ in one-molar solutions of Al(NO₃)₃
and Th(NO₃)₄
| Electrolyte | \(C_{\mathrm{AgBrO_3}}\cdot 10^2\) | \(L'_p : L_p\)¹) | \(L'_i : L_i\)²) | \(a\) |
|---|---|---|---|---|
| Al(NO₃)₃ | 1.83 | 4.93 | 2.22 | 2.664 |
| Th(NO₃)₄ | 2.23 | 7.31 | 2.70 | 2.245 |
¹) \(L'_p\) and \(L_p\) are the solubility product of AgBrO₃, respectively, in a one-molar nitrate solution and in water.
²) \(L'_i\) and \(L_i\) are the solubility of AgBrO₃, respectively, in a one-molar nitrate solution and in water.
Conclusions
The solubility of silver bromate in aqueous solutions of aluminum and thorium nitrates was investigated at concentrations of the external electrolytes from 0.001 to 1 mol/l at 25°.
The experimental data for the system AgBrO₃—Al(NO₃)₃—H₂O were compared with data obtained by us earlier for the systems AgBrO₃—Mg(NO₃)₂—H₂O and AgBrO₃—NaNO₃—H₂O, in order to comparatively assess the influence of the cations of the first three elements of the third period of the periodic system on the solubility of the silver bromate precipitate in the absence of any clearly expressed chemism in the systems.
It was established that, in solutions of equal normality of sodium, magnesium, and aluminum nitrates, the greatest increase in the solubility of silver bromate is caused by sodium nitrate, and the smallest by aluminum nitrate.
The experimental data for the systems AgBrO₃—Al(NO₃)₃—H₂O and AgBrO₃—Th(NO₃)₄—H₂O were used to calculate the value \(a\), by means of which the activity coefficients of silver bromate in aqueous solutions of aluminum and thorium nitrates were determined according to the second variant of the Debye–Hückel formula.
The solubility products and activity products of silver bromate in aqueous solutions of aluminum and thorium nitrates were determined, and the magnitudes of the change in the solubility product in these systems as a function of the ionic strength of the solution were indicated.
References
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