Preparation
Lead tetrachloride may be prepared by dissolving lead dioxide in cold concentrated hydrochloric acid at 0°C:
PbO2 + 4HCl → PbCl4 + 2H2O
However, in the above method some amount of lead dichloride may form, especially if the temperature is above 0°C.
The preferred preparation method is to introduce chlorine into the solution while dissolving lead dioxide in cold concentrated HCl. This prevents decomposition of PbCl4 to PbCl2 and enhances the formation of chloroplumbic acid, H2PbCl6 in solution. Addition of ammonium chloride precipitates out yellow ammonium chloroplumbate, (NH
4)
2PbCl
6 , which is filtered out. The yellow precipitate, on treatment with cold concentrated sulfuric acid, forms lead tetrachloride, which separates out as a yellow oily liquid. The reactions are:
PbO
2 + 6HCl → H
2PbCl
6 + 2H
2O
H
2PbCl
6 + 2NH
4Cl → (NH
4)
2PbCl
6 + 2HCl
(NH
4)
2PbCl
6 + H
2SO
4 → PbCl
4 + (NH
4)
2SO
4 + 2HCl
