Various hydrates of zinc chloride are known:  with n = 1, 1.33, 2.5, 3, and 4.5. However, only the 1.33-hydrate, hemipentahydrate, trihydrate, and the heminonahydrate has been structurally elucidated.
The 1.33-hydrate, previously thought to be the hemitrihydrate, consists of trans-Zn(HO)Cl centers with the chlorine atoms connected to repeating ZnCl chains. The hemipentahydrate, structurally formulated [Zn(HO)][ZnCl], consists of Zn(HO)Cl octahedrons where the chlorine atom is part of a [ZnCl] tetrahedera. The trihydrate consists of distinct hexaaquozinc(II) cations and tetrachlorozincate anions; formulated [Zn(HO)][ZnCl]. Finally, the heminonahydrate, structurally formulated [Zn(HO)][ZnCl]·3HO also consists of distinct hexaaquozinc(II) cations and tetrachlorozincate anions like the trihydrate but has three extra water molecules.