Basic Zinc Chlorides

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 ?H0 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.