Abstract Neodymium trichloride hexahydrate (NdCl 3 · 6H 2O) was dehydrated by heating it in either air, argon, HCl or argon-HCl mixtures to germinate the intermediate species. The hexahydrate (NdCl 3 · 6H 2O) was found to decompose to pentahydrate (NdCl 3 · 5H 2O) which in turn decomposed to tetrahydrate (NdCl 3 · 4H 2O). The latter decomposed to monohydrate (NdCl 3 · H 2O) as the dehydration proceeded towards anhydrous NdCl 3. Simultaneously to dehydration, formation of neodymium oxychloride (NdOCl) and neodymium hydroxychloride (Nd(OH) 2Cl) took place. Nd(OH) 2Cl was isolated and characterized by X-ray diffraction. Its decomposition temperature was determined to be 376°C by differential thermal analysis. Its heat of decomposition to NdOCl and H 2O was determined by differential scanning calorimetry to be 23479 cal mol −1 (98283 J mol −1). Its density was found to be 4.596 g cm −3 at 25 °C.