NaCl doped MgCl2 center dot nEtOH adducts were prepared by ball-milling MgCl2 center dot 2.5EtOH with NaCl. Both the ball-milled MgCl2 center dot nEEtOH/NaCl mixture and pure MgCl2 center dot 2.5EtOH adducts were analyzed by X-ray diffraction (XRD), transmission electron microscope (TEM), thermogravimetry (TG) and differencial scanning calorimetry (DSC). A simple MgCl2 center dot nEtOH/NaCl mixture without ball-milling treatment was also studied for comparison. Two kinds of mixed crystals, Na2MgCl4 and NaMgCl3, were found to be formed in a ball-milled mixture that contained 16 mol.% NaCl. TG and DSC analysis of the samples also provided indirect evidences supporting the presence of the mixed crystals in the ball-milled mixture. Adding certain amounts of NaCl in MgCl2 center dot 2.5EtOH adduct, either by co-milling or by simple mixing, greatly increased the thermal stability of the adduct, but thermal decomposition behaviour of the ball-milled mixture was still different from that of a simple mixture. (c) 2007 Elsevier Ltd. All rights reserved.