Lead

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Lead, a gray heavy soft metal. Used in electronic solders and sometimes in jewellery. It is a very versatile metal and has too many technical usages to mention all here. As lead is toxic it has been phased out in areas where good alternatives exists. The RoHS directive (2003) in EU forced most electronics to use lead free solders. Similar directives have been enforced in the rest of the world too. Lead is still used in lead batteries and bullets.

Contents

Lead as a contaminant

If small amounts of lead is included in refined gold it becomes brittle and looses it's malleability. To avoid that a small amount of sulfuric acid is added to the gold chloride solution before filtering and precipitation.

Chemical reactions of lead

Lead is not attacked by sulfuric or hydrochloric acids. It dissolves in nitric acid with the evolution of nitric oxide gas to form dissolved Pb(NO3)2. The nitrate is a well-soluble solid in water. Mixed with halides, sulfate, chromate or carbonate ions the nitrate will form precipitates. Although the lead chloride forms a precipitate in water, high temperature water can dissolve a lot more lead chloride than cold water.

When lead chloride crystallizes it usually forms long thin needle-like white crystals.

Lead chloride can also be dissolved in strong hydrocloric acid via water soluble complexes.

Lead can also be dissolved in sodium hydroxide mixed with strong hydrogen peroxide. Probably by oxidize metallic lead and the oxide reacts to form sodium plumbate which is soluble in strong sodium hydroxide.

Uses for lead in refining

As lead is resistant to sulfuric acid, it is used as cathode in the Sulfuric acid cell.

Lead is also used in fire assaying, both in the form of foils and as Lead oxide.

This section needs to be expanded.

Lead in the waste stream

Lead is one of the RCRA 8 metals so if it is in the waste stream it can inflict higher costs for treatment.

The EPA Limits for lead both in water and solid waste is 5ppm (mg/l)

To do
  • Add solubility figures for cold and hot water
  • Lead and sulfuric acid, electrode in sulfuric cell, removing lead salt from solutions
  • Add references
  • Other chemistry
  • Lead and lead oxide used in assaying

References

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