Nývlt, J. Journal of Thermal Analysis and Calorimetry (2001) 66: 509. doi:10.1023/A:1013117001627
Literature data of solubility of MgSO3 in water and in aqueous solutions of MgSO4 have been correlated. Magnesium sulfite forms hexahydrate (stable below 40°C) and trihydrate (above 40°C), nevertheless, metastable hexahydrate can precipitate at temperatures significantly higher than this transition temperature. Magnesium sulfate increases the solubility of the sulfite.