Raman Spectroscopic Study of Crystallization from Solutions Containing MgSO4 and Na2SO4: Raman Spectra of Double Salts

Mg2+, Na+, and SO4 2– are common ions in natural systems, and they are usually found in water bodies. Precipitation processes have great importance in environmental studies because they may be part of complex natural cycles; natural formation of atmospheric particulate matter is just one case. In this work, Na2Mg(SO4)2·5H2O (konyaite), Na6Mg(SO4)4 (vanthoffite), and Na12Mg7(SO4)13·15H2O (loeweite) were synthesized and their Raman spectra reported. By slow vaporization (at 20 °C and relative humidity of 60–70%), crystallization experiments were performed within small droplets (diameter ≤ 1–2 mm) of solutions containing MgSO4 and Na2SO4, and crystal formations were studied by Raman spectroscopy. Crystallization of Na2Mg(SO4)2·4H2O (bloedite) was observed, and the formation of salt mixtures was confirmed by Raman spectra. Bloedite, konyaite, and loeweite, as well as Na2SO4 and MgSO4·6H2O, were the components found to occur in different proportions. No crystallization of Na6Mg(SO4)4 (vanthoffite) was observed under the crystallization condition used in this study.