POLYTHERMAL SOLUBILITY OF THE Na2SO4·MgSO4 - NaCl-H2O SYSTEM

ABSTRACT

In this work, the solubility of the Na₂SO₄·MgSO₄ - NaCl-H₂O system was studied using a visual polythermal method. Based on the polytherms of binary systems and internal cross sections, polythermal solubility diagrams of the Na₂SO₄·MgSO₄ - NaCl-H₂O system were constructed in the temperature range from -25.2 to 41.0 °C. When studying the solubility of this system, polytherms were carried out in each temperature range of 10 ° C. On the polythermal solubility diagram the crystallization regions of ice, Na₂SO₄·MgSO₄, MgSO₄·10H₂O, NaCl, NaCl·H₂O, Na₂SO₄·MgSO₄·2H₂O, Na₂SO₄·MgSO₄·4H₂O and compound of the composition MgCl₂ were delimited.  Based on the results of the study, it was revealed that the Na₂SO₄·MgSO₄ - NaCl-H₂O system belongs to a complex eutonic type.

АННОТАЦИЯ

В этой работе было изучено растворимость системы Na₂SO₄·MgSO₄ - NaCl-H₂O с помощью визуального политермического метода. На основе политерм бинарных систем и внутренних сечений было построено политермические диаграммы растворимости системы Na₂SO₄·MgSO₄ - NaCl-H₂O в интервале температур от -25,2 до 41,0 °С. При изучении растворимости этой системы политермы проводились в каждом интервале температур 10 °С. На диаграмме политермической растворимости были выделены области кристаллизации льда, Na₂SO₄·MgSO₄, MgSO₄·10H₂O, NaCl, NaCl·H₂O, Na₂SO₄·MgSO₄·2H₂O, Na₂SO₄·MgSO₄·4H₂O и соединения состава MgCl₂. На основе результатов исследования было выявлено что система Na₂SO₄·MgSO₄ - NaCl-H₂O относится к сложному эвтоническому типу.

Keywords: solubility, system, diagram, magnesium sulfate, sodium sulfate, sodium chloride, crystallization temperatures.

Ключевые слова: растворимость, система, схема, сульфат магния, сульфат натрия, хлорид натрия, температуры кристаллизации.

Introduction

One of the main directions of economic development in developing countries is the exploitation of natural raw materials, the production of competitive, import-substituting products based on local raw materials through its complex processing. Such chemical products include sodium and magnesium sulfates, as the need for these products increases every day with the development of industry and production [1-3].

The laws of solubility of salts and the equilibrium of liquid and solid phases are crucial in establishing the scientific basis for separating or purifying salts, especially those with complex compositions, for various applications [4-7]. Several scientists have conducted modern studies on salt systems to support the production of chemical products and the improvement of technologies [8-10]. In addition, several studies that have researched MgSO₄ and Na₂SO₄ as their objects are known from the literature.

Materials and methodology

The polythermal solubility of the Na₂SO₄·MgSO₄ - NaCl-H₂O system was studied by the visual polythermal method [11]. Liquid nitrogen was used as a freezing reagent in the study of solubility of solutions. In the quantitative chemical analysis of liquid and solid phases, the content of magnesium ions was determined by the complexometric method [12], sodium by flame photometry [13], chloride ions by the Mohr method [14].

Results and discussion

The binary system NaCl-H₂O was previously studied by the authors [15], this system is part of the system we are studying, and our data are in good agreement with the literature data.

The solubility of the Na₂SO₄·MgSO₄ - NaCl-H₂O system was studied using eight internal sections. Based on the results of the study of binary systems and internal sections, a complete polythermal diagram of this system was constructed in the temperature range from -25.2 to 41 °C. The crystallization fields of ice, Na₂SO₄·MgSO₄, MgSO₄·10H₂O, NaCl, NaCl·H₂O, Na₂SO₄·MgSO₄·2H₂O, Na₂SO₄·MgSO₄·4H₂O and a new compound of the system – magnesium chlorides are highlighted on the phase diagram of the solubility of the Na₂SO₄·MgSO₄ - NaCl-H₂O system. These fields converge at six triple nodal points of the system, for which the compositions of the equilibrium solution and their corresponding crystallization temperatures are determined, which are shown in Fig. 1.

Fig. 1. Polythermal diagram of the solubility of the Na₂SO₄·MgSO₄ - NaCl-H₂O system

On the polythermal diagram, the fields of the formed crystals of the system are highlighted in bold lines, and these fields are named accordingly. These fields arise at six triple nodal points of the system, for which the corresponding compositions of the equilibrium solution and crystallization temperatures are determined (Table 1).

Table 1.

Binary and ternary points of Na₂SO₄·MgSO₄ - NaCl-H₂O system.

From the above data, it can be seen that there is no chemical interaction between the components of the system under study. The system belongs to a complex eutonic type.

Conclusion

Thus, the results of the study showed that during the study of the Na₂SO₄·MgSO₄ - NaCl-H₂O system, a new compound is formed as a result of the interaction of the components. This indicates that the system under study belongs to a complex eutonic type. And so, these results provide new scientific data to researchers studying graphical analysis of salt systems.

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