The phase equilibria in the K 2 SO 4 –Rb 2 SO 4 –H 2 SO 4 –H 2 O system have been investigated under isothermal conditions at 25°C. The concentration limits of crystallization of solid solutions with the general formulas (K x Rb 1– x ) 2 SO 4 , (K x Rb 1– x ) 3 H(SO 4 ) 2 , (K x Rb 1– x ) 9 H 7 (SO 4 ) 8 ⋅ H 2 O, and K x Rb 1– x HSO 4 and the K 0.55 Rb 0.45 HSO 4 phases are determined. The dependences of the equilibria of saturated solutions on the initial production conditions are revealed. The growth conditions for large single crystals of complex acid potassium–rubidium sulfates are determined. The phase-equilibrium diagram of the system is constructed.

The phase equilibria in the K2SO4–Rb2SO4–H2SO4–H2O system have been investigated under isothermal conditions at 25°C. The concentration limits of crystallization of solid solutions with the general formulas (KxRb1–x)2SO4, (KxRb1–x)3H(SO4)2, (KxRb1–x)9H7(SO4)8 ⋅ H2O, and KxRb1–xHSO4 and the K0.55Rb0.45HSO4 phases are determined. The dependences of the equilibria of saturated solutions on the initial production conditions are revealed. The growth conditions for large single crystals of complex acid potassium–rubidium sulfates are determined. The phase-equilibrium diagram of the system is constructed.

The phase equilibria in the quaternary water-salt system CsHSO4-CsH2PO4-NH4H2PO4-H2O at a temperature of 40 degrees C have been studied. The method of parallel crystallization was used, which makes it possible to study in a short time such complex objects as multicomponent water-salt systems. The crystallization region and solubility are determined for the following phases: CsHSO4, NH4H2PO4, (Cs,NH4)H2PO4, including (Cs, NH4)4(HSO4)3(H2PO4) and (Cs,NH4)2(HSO4)(H2PO4) obtained for the first time. The Cs3NH4(HSO4)3(H2PO4) and CsNH4(HSO4)(H2PO4) crystals are also obtained for the first time. Primary X-ray diffraction experiments were carried out on the obtained crystals of the solid solution (Cs,NH4)4(HSO4)3(H2PO4) and the solid solution (Cs, NH4)2(HSO4)(H2PO4), to characterize their phase composition and further study the properties.

The conditions for synthesis of [Ni(H2NCH2CH2NH2)3]Cl2 ⋅ 2H2O ([Ni(en)3]Cl2 ⋅ 2H2O) crystals from aqueous solutions have been considered. The synthesized crystals have been comprehensively studied by methods of X-ray powder and single-crystal diffraction, differential scanning calorimetry, and optical spectroscopy.

The paper presents the results of studies on the growth of Rb2NiC14-2H2Ocrystals and the study of their properties. The conditions for the reproducible production of Rb2NiC14-2H2Osingle crystals by the method of controlled decrease of solubility are determined. The optical and thermal properties of crystals obtained in this way were studied.

The phase equilibria in the quaternary water-salt system K2SO4 - (NH4)2SO4 - H2SO4 - H2O at a temperature of 35 °C were studied for the first time. The areas of crystallization, solubility, and reproducible conditions for obtaining crystals of solid solutions were determined: (Ki_ x (NH4) x )2SO4, (Ki. x (NH4) x )3H(SO4)2, (Ki. x (NH4) x )9H7(SO4)8H2O, which are superprotonics. The study of phase equilibria in ternary systems K2SO4 - H2SO4 - H2O and (NH4)2SO4 - H2SO4- H2O was carried out, the solubility values and the solubility character of the compounds (NH4)2SO4 and K2SO4, (NH4)3H(SO4)2 and K3H(SO4)2, K9H7(SO4)8H2O, NH4HSO4 n KHSO4 were determined.

A single crystal of nickel chloride hexahydrate was obtained by isothermal evaporation from an aqueous saturated solution. The transmission spectrum parameters and the thermal stability of the sample were studied.

The crystals of solid solution (NH4,Cs)4(HSO4)3(H2PO4) were investigate by synchronous thermal analysis and polarization microscopy methods at heating with the purpose of studying phase transitions in these solid solutions. The temperatures of structural modifications are established, and it is shown that the replacement of Cs cations by NH4 in Cs4(HSO4)3(H2PO4) crystals leads to a decrease in the temperature of phase transformations.

x Cs 6 H(HSO 4 ) 3 (H 2 PO 4 ) 4 + (1 – x )AlPO 4 — composition proton conducting materials were obtained in the mass range ( x = 0.9–0.7). Their physicochemical and transport properties have been studied by X-ray phase analysis, impedance spectroscopy, and electron scanning microscopy.

Composite proton-conducting materials xCs6H (HSO4) 3 (H2PO4) 4+ (1 - x) AlPO4 were obtained in the composition range (x = 0.9–0.7). The methods of x-ray phase analysis, impedance spectroscopy, electron scanning microscopy studied their physicochemical and transport properties.