Crystallization of sodium chloride dihydrate (hydrohalite)

Abstract The existing literature on the phase diagram of NaCl-H 2 O system and the study of crystallization of sodium chloride dihydrate NaCl·2H 2 O (mineral name hydrohalite) is briefly reviewed first. Then a simple and fast procedure for NaCl·2H 2 O crystallization is described to obtain large enough (∼1 cm long) single crystals in amount of hundreds grams in one batch. This procedure can stimulate the investigation of physico-chemical properties of hydrohalite. The characterization of the crystallized samples with X-ray (single-crystal and powder) diffraction did allow estimating the average volume thermal expansion of hydrohalite as of ∼70∙10 –6 K −1 over temperature range from 100 to 250 K.