Lead halides structure

In the PbCb type of structure, each metal atom has nine nonmetal neighbors, but again the covalence is limited by the metal. For all the seven compounds of this type for which data are available, namely the bromides and iodides of strontium and barium as well as the lead halides except iodide, n = 4. 

Lead fluoride, 193 Lead halides, 197 bivalent structure, 193 Lead iodide, 194 Lead oxide structure, 202 Lead phosphates, 222 Lead selenide structure, 202 Lead sulfate, 222 Lead sulfide structure, 202 Lead tclluride structure, 202 Lewisite, 256 Lipophilicity... 

Fig. 2.24 The crystal Structure of (anthryl-CH2-NHj)2 PbCU-The lead halide layers are separated form each other by molecular double layers. The a, b, and c axes of the unit cell are shown in the figure. From [16].

Fig. 4.2 Structures of some organotin and lead halides in the solid state...

The use of fire retardants in polymers has become more complicated with the realisation that more deaths are probably caused by smoke and toxic combustion products than by fire itself. The suppression of a fire by the use of fire retardants may well result in smouldering and the production of smoke, rather than complete combustion with little smoke evolution. Furthermore, whilst complete combustion of organic materials leads to the formation of simple molecules such as CO2, H2O, N2, SO2 and hydrogen halides, incomplete combustion leads to the production of more complex and noxious materials as well as the simple structured but highly poisonous hydrogen cyanide and carbon monoxide. 

Polystyrene produced by free-radical polymerisation techniques is part syndio-tactic and part atactic in structure and therefore amorphous. In 1955 Natta and his co-workers reported the preparation of substantially isotactic polystyrene using aluminium alkyl-titanium halide catalyst complexes. Similar systems were also patented by Ziegler at about the same time. The use of n-butyl-lithium as a catalyst has been described. Whereas at room temperature atactic polymers are produced, polymerisation at -30°C leads to isotactic polymer, with a narrow molecular weight distribution. 

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