Finally, the simplest method relies on treating the zinc chloride with thionyl chloride. Anhydrous samples can be purified by sublimation in a stream of hydrogen chloride gas, followed by heating the sublimate to 400 ☌ in a stream of dry nitrogen gas. Such samples may be purified by recrystallization from hot dioxane. Unlike many other elements, zinc essentially exists in only one oxidation state, 2+, which simplifies the purification of the chloride.Ĭommercial samples of zinc chloride typically contain water and products from hydrolysis as impurities. ZnS + 2 HCl + 4 H 2O → ZnCl 2(H 2O) 4 + H 2S Hydrated forms and aqueous solutions may be readily prepared similarly by treating Zn metal, zinc carbonate, zinc oxide, and zinc sulfide with hydrochloric acid: Preparation and purification Īnhydrous ZnCl 2 can be prepared from zinc and hydrogen chloride: The tetrahydrate ZnCl 2(H 2O) 4 crystallizes from aqueous solutions of zinc chloride. In the gas phase, ZnCl 2 molecules are linear with a bond length of 205 pm.įive hydrates of zinc chloride are known: ZnCl 2(H 2O) n with n = 1, 1.5, 2.5, 3 and 4. A Raman scattering study of the melt indicated the presence of polymeric structures, and a neutron scattering study indicated the presence of tetrahedral complexes. Molten ZnCl 2 has a high viscosity at its melting point and a comparatively low electrical conductivity, which increases markedly with temperature. Rapid cooling of molten ZnCl 2 gives a glass.
![precipitate symbol precipitate symbol](https://image1.slideserve.com/2778625/slide7-l.jpg)
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A possible explanation is that the OH − ions originating from the absorbed water facilitate the rearrangement. The orthorhombic form (δ) rapidly changes to one of the other forms on exposure to the atmosphere. Here a, b, and c are lattice constants, Z is the number of structure units per unit cell, and ρ is the density calculated from the structure parameters. Each case features tetrahedral Zn 2+ centers. Four crystalline forms ( polymorphs) of ZnCl 2 are known: α, β, γ, and δ.