Basic Zinc Chlorides

Abstract

Two basic zinc chlorides identified by chemical and X-ray analysis as ZnOHCl and ZnCl₂,4Zn(OH)₂,H₂O respectively were prepared. The thermal decomposition of these basic chlorides at temperatures up to 250º may be represented by the equations : 2ZnOHCl + ZnCl₂+ZnO +H₂O (1)and ZnCl₂,4Zn(OH)₂,H₂O → ZnCl₂ +4ZnO +5H₂O (2) Mass spectrometric measurements show that, in proportion to the water, there is little hydrogen chloride evolved on heating. The dissociation pressures of the compounds are given by the equations: ZnOHCl loglop log₁₀P(atm) = -1.93 x 10³/T + 4.22 ZnCl₂,4Zn(OH)₂,HzO log₁₀P (atm) = -1.95 x l0³/T + 3.93 The value of ΔH⁰ for dissociation is approximately the same for the two compounds, namely, 9 kcal/mole. Pure zinc chloride can be separated from zinc chloride contaminated with basic chloride by sublimation along a tube which is being continuously evacuated.