The crystallization in the three-component systems Rb2SO4-MSO4-H2O (M = Mg, Co, Ni, Cu, Zn) is studied by the method of isothermal decrease of supersaturation. It has been established that isostructural double compounds,
Rb2M(SO4)2·6H2O (M = Mg, Co, Ni, Cu, Zn), , crystallize from the ternary solutions within wide
concentration ranges. The infrared spectra are discussed with respect to the normal vibrations of the sulfate ions and water molecules. The unit-cell group theoretical treatment of the double salts is presented. The extent of energetic distortions of guest ions (about 2 mol%) matrix-isolated in the respective selenates, (M' = K, Rb, ; M" = Mg, Co, Ni, Cu, Zn), is commented.
 Chr. Balarew, V. Karaivanova and T. Ojkova, “Beitrag zur Untersuchung der Isomorphenund Isodimorphen Einschluesse in Kristallsalzen. III. Untersuchung der Systeme Zinksulfat-Kobaltsulfat-Wasser und Zinksulfat-Nickelsulfat-Wasser Bei 25°C,” Communications of Departments of Chemistry, Bulgarian Academy of Sciences, Vol. 3, No. 4, 1970, pp. 637-644.
 T. Oykova, D. Mihov and P. Pavlova, “Phase Interaction in the Systems Sodium Selenate-Cupper Selenate-Water and Sodium Selenate-Zinck Selenate-Water at 25°C,” Crystal Research and Technology, Vol. 26, No. 8, 1991, pp. 1071-1075.
 T. Ojkova, D. Stoilova and D. Barkov, “On the Double Salt Formation in the Systems Rb2SeO4-ZnSeO4-H2O and Cs2SeO4-ZnSeO4-H2O at 25°C,” Monatshefte für Chemie, Vol. 131, No. 10, 2000, pp. 1019-1023.
 V. Karadjova, “Crystallization in the Three-Component Systems Rb2SeO4-MeSeO4-H2O (Me = Mg, Ni, Cu) at 25°C,” Journal of University of Chemical Technology and Metallurgy, Vol. 48, No. 3, 2013, pp. 316-325.
 M. Georgiev, D. Marinova and D. Stoilova, “Infrared Spectroscopic Study of Tutton Compounds. I. Vibrational Behavior of Ions Included in
Me2'Me''(SeO4)2·6H2O(Me'= K, NH4; Me'' = Mg, Co, Ni, Cu, Zn),” Journal of University of Chemical Technology and Metallurgy, Vol. 45, No. 1, 2010, pp. 75-82.
 D. L. Rousseau, R. P. Bauman and S. P. Porto, “Normal Mode Determination in Crystals,” Journal of Raman Spectroscopy, Vol. 10, No. 1, 1981, pp. 253-290.
 V. Ananthanarayanan, “Studies on the Vibrational Spectrum of the SO4 Ion in Crystalline M2'M''(SO4)2·6H2O(M’= K or NH4, and M'' = Mg, Zn, Ni, or Co): Observations on the Symmetry of the Sulfate Ion in Crystals,” Journal of Chemical Physics, Vol. 48, No. 2, 1968, pp. 573-581.
 R. G. Brown and S. D. Ross, “Forbidden Transitions in the Infrared Spectra of Tetrahedral Anions—VI. Tutton Salts and Other Double Sulfates and Selenates,” Spectrochimica Acta, Vol. 26A, No. 4, 1970, pp. 945-958.
 J. A. Campbell, D. P. Ryan and L. M. Simpson, “Interionic Forces in Crystal—II. Infrared Spectra of SO4 Groups and ‘Octahedrally’ Coordinated Water in Some Alums, Tutton Salts, and the Double Salts Obtained by Dehydrating Them,” Spectrochimica Acta, Vol. 26A, No. 12, 1970, pp. 2351-2361.
 S. Gupta, B. Singh and B. Khanna, “The Vibrational Spectra of Ions in the Hydrated Double Sulfates: the Tutton Salts,” Journal of Molecular Structure, Vol. 112, No. 1-2, 1984, pp. 41-49.
 V. Ivanovski, Th. Mayerhöfer and J. Popp, “Investigation of the Peculiarities in the Polarized Reflectance Spectra of Some Tutton Salt Monoclinic Single Crystals Using Dispersion Analysis,” Vibrational Spectroscopy, Vol. 44, No. 2, 2007, pp. 369-374.
 M. Georgiev, D. Marinova and D. Stoilova, “Infrared Spectroscopic Study of Tutton Compounds. II. Vibrational Behavior of NH+4 Ions Included in K2Me''(XO4)2·6H2O (Me''= Mg, Co, Ni, Cu, Zn; X = S, Se),” Journal of University of Chemical Technology and Metallurgy, Vol. 45, No. 2, 2010, pp. 195-200.
 Zd. Micka, L. Prokopová, I. Císarová and D. Havlícek, “Crystal Structure, Thermoanalytical Properties and Infrared Spectra of Double Magnesium Selenates,” Collection of Czechoslovak Chemical Communications, Vol. 61, No. 9, 1996, pp. 1295-1306.
 H. D. Lutz, “Bonding and Structure of Water Molecules in Solid Hydrates. Correlation of Spectroscopic and Structural Data,” Structure & Bonding (Berlin), Vol. 69, 1988, pp. 97-123. http://dx.doi.org/10.1007/3-540-18790-1_3
 H. D. Lutz, E. Alici and T. Kellersohn, “Single Crystal Raman Studies on Sr(CIO3)2 and and Ions Matrix Isolated in Sr(CIO3)2,” Journal of Raman Spectroscopy, Vol. 21, No. 7, 1990, pp. 387-393.
 H. D. Lutz, “Crystal Matrix and Crystal Double Spectroscopy,” Journal of Molecular Structure, Vol. 704, No. 1-3, 2004, pp. 71-78.
 H. D. Lutz, H. Christian and W. Eckers, “Infrared and Single Crystal Raman Studies of Alkaline Earth Chlorate, Bromated and Iodate Monohydrates and of Halite Ions Matrix Isolated in Ba(CIO3)2·H2O Type Host Lattice,” Spectrochimica Acta, Vol. 41A, No. 4, 1985, pp. 637-642.
 H. D. Lutz, T. Kellersohn, B. Müller and J. Henning, “Infrared and Raman Studies of Halite Ions Matrix Isolated in Sr(CIO3)2 and Sr(CIO3)2·H2O Type Host Lattices,” Spectrochimica Acta, Vol. A44, No. 5, 1988, pp. 497-504.
 L. Pejov and V. Petrusevski, “Infrared Spectra of Sulfate Ions Trapped in Rubidium and Cesium Selenate: Harmonic Frequencies and Anharmonicity Constants for Antisymmetric SO4 Stretching Vibrations,” Journal of Molecular Structure, Vol. 482/483, 1999, pp. 257-262.
 V. Petrusevski and W. F. Sherman, “Harmonic Frequensies and Anharmonicity Constants for the Antisymmetric SO4 Stretching Vibrations of Isomorphously Isolated SO4 Ions in K2CrO4,” Journal of Molecular Structure, Vol. 219, No. 1-2, 1990, pp. 171-176.
 L. Pejov and W. F. Sherman, “Infrared Spectra of the Sulfate Ions Trapped in Potassium Selenate—A Comparison with Sulfate Doped Potassium Chromate,” Bulletin of Chemists and Technologists of Macedonia, Vol. 13, No. 2, 1994, pp. 69-76.
 L. Pejov and V. Petrusevski, “The Vibrational Stark Shifts of Sulfate Internal Modes in Doped Potassium, Rubidium and Cesium Selenates. A Quantum Model for Measurement of Crystalline Fields,” Croatica Chemica Acta, Vol. 73, No. 4, 2000, pp. 1171-1184.
 L. Pejov and V. Petrusevski, “Vibrational Anharmonicity and Vibrational Stark Effect of Sulfate Ions Trapped in Potassium, Rubidium and cesiUm Chromate,” Spectrochimica Acta, Vol. A56, No. 5, 2000, pp. 947-957.
 L. Pejov and V. Petrusevski, “Vibrational Anharmonicity and Reorientation Dynamics of Anions Isolated in an Ag2SeO4 Matrix,” Journal of Physics and Chemistry of Solids, Vol. 62, No. 3, 2001, pp. 521-530.
 L. Pejov and V. Petrusevski, “Fourier Transform Infrared Study of Perchlorate ( and ) Anions Isomorphously Isolated in Potassium Permanganate Matrix. Vibrational Anharmonicity and Pseudo-Symmetry Effects,” Journal of Physics and Chemistry of Solids, Vol. 63, No. 5, 2002, pp. 1873-1881.
 L. Pejov and V. Petrusevski, “Infrared Spectra of Permanganate Anions in Potassium Perchlorate Matrices: Vibrational Anharmonicity, Effective Symmetry and Vibrational Mode Mixing Effects,” Spectrochimica Acta, Vol. A58, No. 13, 2002, pp. 2991-3002.
 L. Pejov and V. Petrusevski, “Latent Symmetry versus Accidental Degeneracy Effects in the Vibrational Spectra of Dopant Chromate Anions in M2CrxS1-xO4 Solid Solutions (M = K, Rb, Cs),” Journal of Physics and Chemistry of Solids, Vol. 64, No. 8, 2003, pp. 1353-1363.
 D. Stoilova, M. Georgiev and D. Marinova, “Infrared Study of the Vibrational Behavior of Guest Ions Matrix-Isolated in Metal (II) Sulfates (Me = Ca, Sr, Ba, Pb)”, Journal of Molecular Structure, Vol. 738, No. 1-3, 2005, pp. 211-215.
 D. Stoilova, M. Georgiev and D. Marinova, “Infrared Study of the Vibrational Behavior of Guest Ions Matrix-Isolated in Metal (II) Chromates (Me = Ca, Sr, Ba),” Vibrational Spectroscopy, Vol. 39, No. 1, 2005, pp. 46-49. http://dx.doi.org/10.1016/j.vibspec.2004.10.007
 A. Cahil, B. Soptrajanov, M. Najdoski, H. D. Lutz, B. Engelen and V. Stefov, “Infrared and Raman Spectra of Magnesium Ammonium Phosphate Hexahydrate (Struvite) and Its Isomorphous Analogues. Part VI: FT-IR Spectra of Isomorphously Isolated Species. Ions Isolated in MKPO4·6H2O (M = Mg; Ni) and Ions Isolated in MgNH4AsO4·6H2O,” Journal of Molecular Structure, Vol. 876, No. 1-3, 2008, pp. 255-259.
 D. Stoilova, D. Marinova, M. Wildner and M. Georgiev, “Comparative Study on Energetic Distortions of Ions Matrix-Isolated in Compounds with Kröhnkite-Type Chains, K2Me(CrO4)2·2H2O and Na2Me(SeO4)2·2H2O (Me = Mg, Co, Ni, Zn, Cd),” Solid State Sciences, Vol. 11, No. 12, 2009, pp. 2044-2050.
 D. Stoilova and H. D. Lutz, “Infrared Study of the Vibrational Behavior of the S-O Stretching Modes in Kieserite-Type Selenates MeSeO4·H2O with Matrix-Isolated and Me2+ Guest Ions (Me = Mn, Co, Ni, Zn),” Journal of Molecular Structure, Vol. 606, No. 1-3, 2002, pp. 267-272.
 D. Stoilova, “Influence of the Crystal Field Stabilization Energy of Metal(II) Ions on the Structural Distortion of Matrix-Isolated Guest Ions in Selenate Matrices,” Spectrochimica Acta A: Molecular and Biomolecular Spectroscopy, Vol. 60, No. 10, 2004, pp. 2243-2251.