Phase equilibria in the Na,Ca//SO4,CO3,HCO3–H2O system at 0 °C 24 D O I: 1 0. 15 82 6/ ch im te ch .2 01 9. 6. 1. 03 Soliev L., Jumaev M. T. Chimica Techno Acta. 2019. Vol. 6, No. 1. P. 24–30. ISSN 2409–5613 L. Soliev, M. T. Jumaev Tajik State Pedagogical University named after S. Ayni, Dushanbe, 734025, Republic of Tajikistan e-mail: soliev.lutfullo@yandex.com; jumaev_m@bk.ru Phase equilibria in the Na,Ca//SO4,CO3,HCO3–H2O system at 0 °C Phase equilibria in the Na,Ca//SO4,CO3,HCO3-H2O system have been studied at 0 °C. The studied system at 0 °C involves 4 invariant points, 13 monovari- ant curves and 15 divariant fields. The obtained results served as a basis for the construction of phase diagram (phase complex) of the studied system at 0 °C. Keywords: system; phase equilibria; diagram; geometric images Received: 12.02.2019. Accepted: 05.03.2019. Published: 29.03.2019. © Soliev L., Jumaev M. T., 2019 Results and discussion The laws of  phase equilibria in the Na,Ca//SO4,CO3,HCO3-H2O system are not only of scientific interest, but also necessary for elaboration of optimal condi- tions for halurgicol processing of natural mineral raw materials and industrial wastes containing sulfates, carbonates, hydrocar- bonates of sodium and calcium. However, these equilibria have not been studied yet, and necessary information is absent in the available literature [1]. We have studied phase equilibria in the Na,Ca,//SO4,CO3,HCO3-H2O system at 0 °C by the translation method which follows from the principle of compatibility of  the structural elements for  the n and n+1 component systems in one diagram [2]. According to the translation method, the subsequent (n+1) component is added to the n-component system, and the latter is translated to the n+1 component state by the transformation of geometric images of the n-component system. Transformed geometric images have formed correspond- ing phase diagram components on  the n+1 level, according to their topological properties (fields, curved, points), taking into account the Gibbs phase rule for the n+1 component system. More detailed de- scription of  the translation method that can be used for predicting and construct- ing of equilibrium phase diagrams for the multicomponent water — salt systems are considered in the works [3–5]. Previously, this method was used to  study the five- component system [6]. Five-component Na,Ca,//SO4, CO3, HCO3–H2O system includes the follow- ing four 4-component systems: Na2SO4– Na2CO3–NaHCO3–H2O; CaSO4–Ca- CO3-Ca(HCO3)2–H2O; Na,Ca,//SO4, CO3–H2O; Na,Ca,//SO4, HCO3–H2O; Na,Ca,//CO3, HCO3–H2O. Phase compo- sition of invariant points in the aforemen- tioned 4-component systems have been determined by both the solubility method [1] and the translation method [7–10] de- scribed earlier. 25 Coexisting equilibrium solid phases, representing the invariant points in  the 4-component systems, are listed in Table 1. In Table 1 and further, E denotes an invariant point where the superscript de- notes its multiplicity (component of  the system), and the subscript denotes its se- quence number. The following notation for  the equilibrium solid phases have been used: Mb  — mirabilite, Na2SO4  · 10H2O; CaG — calcium hydrocarbonate, Ca(HCO3)2; Gp — gypsum CaSO4·2H2O; Nk — nakhcolite, NaHCO3; Gl — gaylus- site Na2CO3·CaCO3·5H2O; Cc  — calcite CaCO3, C  ·  10  — tenfold hydrogenated sodium carbonate Na2CO3 · 10H2O. Fig.  1, which is drawn based on  the data from Table 1, illustrates the equi- librium phase diagram (phase complex) for the Na,Ca,//SO4,CO3,HCO3-H2O sys- tem at 0 °C at the four-component com- positional level, where the salt part of the system forms four-sided prism sweep. After its unification (combining identical crystal- lization fields of the opposite four-compo- nent systems), we obtained a schematic di- agram [11] for the phase equilibrium in the Na,Ca//SO4,CO3,HCO3-H2O system at 0 °C at the four-component compositional level, which is shown in Fig. 2. The constructed diagram contains vari- ous geometric images (invariant points, multi-variant curves, divariant fields) for  the studied system and correspon- dent equilibrium solid phases at the four- component compositional level. The phase composition of the precipitation of quad- ruple invariant points is given in Table 1. The phase composition of the precipitates inside the divariant fields is shown in Fig. 2. The phase composition of the sediments, corresponding to the multi-variant curves that connect four-phase invariant points, can be represented as follows: E1 4 E2 4 = Mb+Nk; E1 4 E5 4 = Mb+C·10; E1 4 E8 4 = C·10+Nk; E2 4 E3 4 = Nk+Gp; E2 4 E7 4 = Gp+Mb; E3 4 E4 4 = CaG+Gp; E3 4 E10 4 = Nk+CaG; E4 4 E6 4 = Gp+Cc; E4 4 E9 4 = Cc+CaG; E5 4 E7 4 = Mb+Gl; E5 4 E8 4 = Gl+C·10; E6 4 E7 4 = Gp+Gl; E6 4 E9 4 = Gl+Cc; E8 4 E10 4 = Nk+Gl; E9 4 E10 4 = Gl+CaG. Table 1 Phase composition of precipitates for the invariant points in the 4-component systems, which are compile the complex 5-component Na,Ca,//SO4,CO3,HCO3-H2O system at 0 °C Invariant points Solid phases in equilibrium Invariant points Solid phases in equilibrium Na2SO4–Na2CO3–NaHCO3–H2O system Na,Ca||SO4,CO3–H2O system E1 4 Mb+Nk+C·10 E5 4 Gl+Mb+C·10 Na,Ca||SO4,HCO3-H2O system E6 4 Gp+Gl+Cc E2 4 Gp+Mb+Nk E7 4 Gl+Gp+Mb E3 4 Gp+Nk+CaG Na,Ca||CO3,HCO3–H2O system CaSO4–CaCO3–Ca(HCO3)2–H2O system E8 4 Gl+Nk+C·10 E4 4 Gp+Cc+CaG E9 4 Gl+Cc+CaG E10 4 Nk+Gl+CaG 26 A translation procedure [3–5] of  in- variant points from the four-component compositional level to a five-component level leads to the formation of the follow- ing five invariant points with the following coexisted in equilibrium solid phases: E1 4 + E5 4 + E8 4 E1 5 = Nk + Mb + + C·10 + Gl; E2 4 + E7 4 E2 5 = Nk + Mb + Gp + + Gl; E3 4 + E10 4 E3 5 = Nk + CaG + Gp + + Gl; E4 4 + E6 4 + E9 4 E4 5 = Gp + Cc + + CaG + Gl. The equilibrium phase diagram for the Na,Ca//SO4,CO3,HCO3-H2O system at 0 °C constructed by the translation method is shown in Fig. 3. The thin solid lines in Fig. 3 indicate the multivariant curves belonging to the four-component compositional level. The correspondent solid phases that coexisted in  equilibrium have been shown above. The dashed lines with arrows indicate monovariant curves belonging to the five- component compositional level. The equi- librium solid phases, which corresponded to these monovariant curves, are identi- cal to the equilibrium solid phases of the translated invariant points in  the corre- sponding quadruple systems. The arrows on  these curves indicate the directions Fig. 1. Prism sweep of the salt part of equilibrium phase diagram for the Na,Ca// SO4,CO3,HCO3-H2O system at 0 °C at the four-component composition level 2NaHCO3 2NaHCO32NaHCO3 Nk Nk Nk E1 4 Mb Mb Mb C·10 C·10 C·10 Na2SO4 Na2CO3 Gp Gp Gp Ca(HCO3)2 Ca(HCO3)2Ca(HCO3)2 CaSO4 CaCO3 Gl Gl Cc Cc Cc CaGCaG CaG E2 4 E3 4 E5 4 E7 4 E6 4 E4 4 E10 4 E8 4 E9 4 27 Fig. 2. Schematic diagram for the phase equilibrium in the Na,Ca//SO4,CO3,HCO3-H2O system at 0 °C at the four-component compositional level, constructed by the translation method Nk E1 4 E2 4 E1 4 Mb C·10 Gp Gl Cc CaG E2 4 E3 4 E3 4 E8 4 E10 4 E5 4 E7 4 E6 4 E4 4 E10 4 E8 4 E9 4 Fig. 3. Schematic phase diagram for the Na,Ca//SO4,CO3,HCO3-H2O system at 0 °C at the five-component compositional level constructed by the translation method E1 5 E3 5 E1 4 E2 4 E2 5 E3 4 E4 5 E5 4 E7 4 E6 4 E4 4 E10 4 E8 4 E9 4 28 Table 2 Equilibrium solid phases and contours of the divariant fields in the Na,Ca//SO4,CO3,HCO3-H2O system at 0 °C Equilibrium solid phases in the fields Field contours in the diagram (Fig. 3) Equilibrium solid phases in the fields Field contours in the diagram (Fig. 3) Mb+Nk E1 4 E1 5 E2 4 E2 5 Cc+CaG E4 4 E4 5 E9 4 Mb+C·10 E1 4 E1 5 E5 4 Mb+Gl E5 4 E1 5 E7 4 E2 5 C·10+Nk E1 4 E1 5 E8 4 Gl+C·10 E1 4 E1 5 E8 4 Nk+Gp E2 4 E2 5 E3 4 E3 5 Gl+Gp E6 4 E4 5 E7 4 E2 5 E3 5 Mb+Gp E2 4 E2 5 E7 4 Gl+Cc E6 4 E4 5 E9 4 CaG+Gp E3 4 E3 5 E4 4 E4 5 Gl+Nk E8 4 E1 5 E2 5 E10 4 E3 5 CaG+Nk E3 4 E3 5 E10 4 Gl+CaG E9 4 E4 5 E10 4 E3 5 Cc+Gp E4 4 E4 5 E6 4 29 of translation. The bold lines also denote monovariant curves belonging to the five- component compositional level. These lines connect five-phase invariant points; equilibrium solid phases correspondent to these lines are: E1 5 E2 5 = Nk + Mb + Gl; E2 5 E3 5 = Gp + Nk + Gl; E3 5 E4 5 = CaG + Gl + Gp. Table 2 shows the equilibrium solid phases and contours of the divariant fields in the Na,Ca//SO4,CO3,HCO3–H2O system at 0 °C. All 15 divariant fields that characte- rized phase equilibria in the studied sys- tem at 0 °C were formed as a result of the translation procedure transforming mono- variant curves to the five-component com- position level. Conclusions Finally, we can conclude that studied Na,Ca//SO4,CO3,HCO3-H2O system at 0 °C has been described at the four-component compositional level (A) and the five-com- ponent compositional level (B) by particu- lar amounts of specific geometric images. Compositional level A B Nonvariant points 10 4 Monovariant curves 15 13 Divariant fields 7 15 References 1. Experimental Solubility Data for Multinary Water — Salt Systems: Handbook. 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