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Lead(II) oxide
Lead(II) oxide, also called lead monoxide, is the inorganic compound with the molecular formula PbO. It occurs in two polymorphs: litharge having a tetragonal crystal structure, and massicot having an orthorhombic crystal structure. Modern applications for PbO are mostly in lead-based industrial glass and industrial ceramics, including computer components.
Lead oxide exists in two polymorphs:
PbO may be prepared by heating lead metal in air at approximately 600 °C (1,100 °F). At this temperature it is also the end product of decomposition of other oxides of lead in air:
Thermal decomposition of lead(II) nitrate or lead(II) carbonate also results in the formation of PbO:
PbO is produced on a large scale as an intermediate product in refining raw lead ores into metallic lead. The usual lead ore is galena (lead(II) sulfide). At a temperature of around 1,000 °C (1,800 °F) in air, the sulfide converted to the oxide:
Lead combusts at high temperature. According to the Barton pot method, refined molten lead droplets are oxidized under a forced air flow which carries them out to the separation system (e.g. cyclonic separators) for further processing. Oxides produced by this method are mostly a mixture of α-PbO and β-PbO. The overall reaction, which is conducted at 450 °C is:
Using a Ball mill, lead balls are oxidized in a cooled rotating drum. The oxidation is achieved by collisions of the balls. Just like in Barton pot method, the supply of air and separators may also be used.
As determined by X-ray crystallography, both polymorphs, tetragonal and orthorhombic feature a pyramidal four-coordinate lead center. In the tetragonal form the four lead–oxygen bonds have the same length, but in the orthorhombic two are shorter and two longer. The pyramidal nature indicates the presence of a stereochemically active lone pair of electrons. When PbO occurs in tetragonal lattice structure it is called litharge; and when the PbO has orthorhombic lattice structure it is called massicot. The PbO can be changed from massicot to litharge or vice versa by controlled heating and cooling. The tetragonal form is usually red or orange color, while the orthorhombic is usually yellow or orange, but the color is not a very reliable indicator of the structure. The tetragonal and orthorhombic forms of PbO occur naturally as rare minerals.
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Lead(II) oxide
Lead(II) oxide, also called lead monoxide, is the inorganic compound with the molecular formula PbO. It occurs in two polymorphs: litharge having a tetragonal crystal structure, and massicot having an orthorhombic crystal structure. Modern applications for PbO are mostly in lead-based industrial glass and industrial ceramics, including computer components.
Lead oxide exists in two polymorphs:
PbO may be prepared by heating lead metal in air at approximately 600 °C (1,100 °F). At this temperature it is also the end product of decomposition of other oxides of lead in air:
Thermal decomposition of lead(II) nitrate or lead(II) carbonate also results in the formation of PbO:
PbO is produced on a large scale as an intermediate product in refining raw lead ores into metallic lead. The usual lead ore is galena (lead(II) sulfide). At a temperature of around 1,000 °C (1,800 °F) in air, the sulfide converted to the oxide:
Lead combusts at high temperature. According to the Barton pot method, refined molten lead droplets are oxidized under a forced air flow which carries them out to the separation system (e.g. cyclonic separators) for further processing. Oxides produced by this method are mostly a mixture of α-PbO and β-PbO. The overall reaction, which is conducted at 450 °C is:
Using a Ball mill, lead balls are oxidized in a cooled rotating drum. The oxidation is achieved by collisions of the balls. Just like in Barton pot method, the supply of air and separators may also be used.
As determined by X-ray crystallography, both polymorphs, tetragonal and orthorhombic feature a pyramidal four-coordinate lead center. In the tetragonal form the four lead–oxygen bonds have the same length, but in the orthorhombic two are shorter and two longer. The pyramidal nature indicates the presence of a stereochemically active lone pair of electrons. When PbO occurs in tetragonal lattice structure it is called litharge; and when the PbO has orthorhombic lattice structure it is called massicot. The PbO can be changed from massicot to litharge or vice versa by controlled heating and cooling. The tetragonal form is usually red or orange color, while the orthorhombic is usually yellow or orange, but the color is not a very reliable indicator of the structure. The tetragonal and orthorhombic forms of PbO occur naturally as rare minerals.