Occurrence and Uses
Lead carbonate occurs in nature as the mineral cerussite. It has several applications. The compound is used in high pressure lubricating greases; as a coating on polyvinyl chloride to improve the dielectric properties of the polymers; in the PVC friction liners for pulleys; in corrosion-resistant grids in lead-storage batteries; in heat-sensitive sheets for thermographic copying; as a photoconductor in electrophotography; in thermistors; and in waxes for steel cables. Another major application of this compound is in catalysis—to catalyze polymerization of formaldehyde to high molecular weight polymeric products and to accelerate the process of curing of moldable thermosetting silicone resins.
Physical Properties
Colorless orthorhombic crystals; refractive index 1.804; Moh’s hardness 3–3.5; density 6.60 g/cm3; decomposes on heating at 315°C; practically insoluble in water (1.1 mg/L at 20°C); KSP 1.46x10–13 at 25°C; also insoluble in alcohol and ammonia; soluble in acids and alkalies.
Preparation
Lead carbonate is prepared by passing carbon dioxide into a cold dilute solution of lead acetate:
Pb(C2H3O2)2 + CO2 + H2O → PbCO3 + CH3COOH
The compound also is prepared in the laboratory by adding sodium bicarbonate to a cold dilute solution of a lead(II) salt, such as lead nitrate or acetate:
Pb2+ + 2HCO3¯ → PbCO3 + CO2 + H2O
Reactions
When heated at 315°C, lead carbonate decomposes to lead oxide and carbon dioxide:
PbCO3→PbO + CO2
When heated in water, it transforms to basic lead carbonate, 2PbCO3•Pb(OH)2
3PbCO3 + H2O → 2PbCO3•Pb(OH)2 + CO2
Lead carbonate dissolves in acids, forming the corresponding lead salt and evolving carbon dioxide:
PbCO3 + 2HCl → PbCl2 + H2O + CO2
Reaction with concentrated acetic acid yields anhydrous lead(II) acetate.
Fusion with boric acid at high temperature forms lead metaborate that has an approximate composition Pb(BO2)2•H2O. The product loses water of crystallization at 160°C.
Toxicity
Although an insoluble salt of lead, the compound exhibits low-to-moderate systemic effects from ingestion in humans. The effects are gastrointestinal contractions, jaundice, convulsions, nausea or vomiting, and degenerative changes in the brain (Lewis (Sr.), R. J. 1996. Sax’s Dangerous Properties of Industrial Materials, 9th ed. New York: Van Nostrand Reinhold).
Chemical Properties
colorless ortho-rhomb crystal(s); made by adding CO2 to a cold dilute solution of lead acetate; many uses such as a catalyst for organic reactions, in high temp greases, as a photoconductor in electrophotography [KIR78]
Chemical Properties
Lead carbonate forms colorless orthorhombic crystals; it decomposes at about 315 °C. It is nearly insoluble in cold water (0.00011 g/100 mL at 20 °C), but is transformed in hot water to the basic carbonate, 2PbCO3·Pb(OH)2. Lead carbonate is soluble in acids and alkalies, but insoluble in alcohol and ammonia.
Uses
Lead carbonate (PbCO3) is found in nature as cerussite. It can also be produced in the
laboratory by reacting sodium carbonate with chlorine. It is a crystalline poison that was, and
to a lesser extent still is, used as a pigment in white house paints.
Uses
Lead carbonate has a wide range of applications. It catalyzes the polymerization of formaldehyde to high molecular weight crystalline poly(oxymethylene) products. It is used in poly(vinyl chloride) friction liners for pulleys on drive cables of hoisting engines. To improve the bond of polychloroprene to metals in wire-reinforced hoses, 10–25 parts of lead carbonate are used in the elastomer. Lead carbonate is used as a component of high pressure lubricating greases; as a catalyst in the curing of moldable thermosetting silicone resins; as a coating on vinyl chloride polymers to improve their dielectric properties; as a component of corrosion-resistant, dispersion-strengthened grids in lead–acid storage batteries; as a photoconductor for electrophotography; as a coating on heatsensitive sheets for thermographic copying; as a component of a lubricantstabilizer for poly(vinyl chloride); as a component in the manufacture of thermistors, and as a component in slip-preventing waxes for steel cables to provide higher wear resistance.
Uses
Preparation of lead standard solutions
Definition
A naturally occurring
form of lead(II) carbonate that is an
important lead ore. It forms orthorhombic
crystals and is often found together with
galena (PbS).
Production Methods
Lead carbonate is prepared by passing CO2 into a cold dilute solution of lead acetate, or by shaking a suspension of a lead salt less soluble than the carbonate with ammonium carbonate at a low temperature to avoid formation of basic lead carbonate.
Definition
cerussite: An ore of lead consistingof lead carbonate, PbCO
3. It is usuallyof secondary origin, formed by theweathering of galena. Pure cerussiteis white but the mineral may be grey due to the presence of impurities. Itforms well-shaped orthorhombiccrystals. It occurs in the USA, Spain,and SW Africa.
