Polythermal Crystallization Behavior of the Mg(ClO₃)₂–[80 wt% 2-Amino-1,3,4-Thiadiazole + 20 wt% Ethanol]–H₂O Pseudo-ternary System

Abstract

Aim: To investigate the polythermal crystallization behaviour of the Mg(ClO₃)₂–[80 wt% 2-amino-1,3,4-thiadiazole + 20 wt% ethanol]–H₂O pseudo-ternary system and to characterize an isolated magnesium-chlorate/thiadiazole-containing solid. Study Design: An experimental physicochemical study using visual polythermal measurements and complementary solid-state and physicochemical characterization. Place and Duration of Study: The work was conducted in the scientific laboratories of the Institute of General and Inorganic Chemistry of the Academy of Sciences of the Republic of Uzbekistan and Navoi State University of Mining and Technologies during 2024–2026. Methodology: The organic stock mixture containing 80 wt% 2-amino-1,3,4-thiadiazole and 20 wt% ethanol was treated as a single pseudo-component. Two boundary systems and six internal sections were examined by the visual polythermal method over the experimentally recorded range from -57.2 to +27.2 °C. The available dataset provides working crystallization temperatures but not point-by-point cooling/heating rates or replicate statistics; accordingly, the values are interpreted as operational crystallization observations rather than statistically characterized equilibrium saturation temperatures. The starting magnesium chlorate hydrate was examined by X-ray diffraction (XRD) and FTIR spectroscopy, whereas the isolated product was examined by X-ray fluorescence (XRF), FTIR spectroscopy, differential thermal/thermogravimetric analysis (DTA/TGA/DTG), and scanning electron microscopy with energy-dispersive X-ray analysis (SEM/EDS). Results: The Mg(ClO₃)₂–H₂O boundary contained a reported low-temperature crystallization point at -52.0 °C for 36.9 wt% nominal Mg(ClO₃)₂, whereas the organic pseudo-component–H₂O boundary contained a point at -27.5 °C for 2.0 wt% pseudo-component. Across the reported pseudo-ternary compositions, crystallization temperatures ranged from -57.2 to +27.2 °C. The working diagram contains regions associated with ice, 2-amino-1,3,4-thiadiazole, and provisionally assigned magnesium chlorate hydrate phase(s). XRF/EDS, FTIR, and thermal analysis jointly support the presence of a magnesium-chlorate/thiadiazole-containing solid, but they do not establish a unique coordination geometry or exact empirical formula. Conclusion: The addition of the 2-amino-1,3,4-thiadiazole/ethanol pseudo-component altered the observed crystallization-temperature profile of the magnesium chlorate–water formulation space. Because Mg(ClO₃)₂·6H₂O was used experimentally while the reported diagram labels the salt coordinate as Mg(ClO₃)₂ and the treatment of crystal water cannot be reconstructed from the available mass-balance record, the plotted compositions are retained as nominal reported formulation coordinates. The study therefore provides a working composition–temperature crystallization map and a physicochemical basis for subsequent phase-pure structural and application-oriented studies; no conclusion regarding field efficacy or environmental safety is drawn.