| Abstract: | Solid products of the reaction between orthorhombic lead monoxide and cold aqueous lead nitrate solutions in the range of molar proportions 1:3 to 3:1 PbO: Pb(NO3)2 have been studied by X-ray powder diffraction (X.R.P.D.). Three distinct crystalline phases were recognised. Reasonably pure samples of monobasic lead nitrate dihydrate dilead (II) monoxide dinitrate dihydrate], PbO.Pb(NO3)2.2H2O, were obtained at temperatures below 20 °C when the reactants were in the range of molar proportions 1:3 to 1:1 PbO: Pb(NO3)2. This compound seems to be stable below 20 °C, but it partially dehydrates at higher temperatures. It does not seem to have been reported elsewhere. Monobasic lead nitrate monohydrate dilead (II) monoxide dinitrate monohydrate], PbO.Pb(NO3)2.H2O, was formed in isolation at temperatures between 25 and 30 °C when the reactants were in the range of molar proportions 1:3 to 1:1 PbO: Pb(NO3)2. This compound is stable at room temperatures, and is identical to phases which have been reported by other authors. Mixtures of these two substances were obtained at temperatures between 20 and 25 °C. Tribasic lead nitrate trihydrate tetra lead (II) trioxide dinitrate trihydrate], 3PbO.Pb(NO3)2.3H2O, was formed in isolation at all temperatures in the range 15 to 30 °C when the reactants were in the molar proportion 3:1 PbO: Pb(NO3)2. This compound seems to be stable at room temperatures and has been reported elsewhere. When the reactants were in the molar proportion 2:1 PbO: Pb(NO3)2, mixtures of tribasic lead nitrate trihydrate with one or other (or both, depending on the temperature) of the monobasic lead nitrate hydrates were obtained. X.R.P.D. data are given for these three compounds, and a critical assessment is made of all the results in the cases of the two compounds for which published data already exists. Also, it is suggested that compounds of stoichiometries intermediate between that of a monobasic lead nitrate hydrate and that of a tribasic lead nitrate hydrate (and which have been described in the literature) can be only metastable in contact with water. The nomenclature used in this paper follows common industrial practise in naming basic lead compounds. However, scientific names are also given in parentheses when necessary. |
