COLOROBBIA Lead Oxide Division

Lead (from the Latin "plumbum" heavy), is a dense metallic element, of a grey-blue colour, which belongs to the Group IVB (or 14) of the periodic table. Probably one of the most ancient metals known, it was used by the Romans to create conduit for the distribution of water together with tin alloys.

Metallic lead is soft, pliable and flexible and, if slightly heated, it can be passed through little holes. It is little resistant to tensile stress and is a poor conductor of electricity. If exposed to air it rapidly changes aspect and takes on a rather opaque blue–grey colour, very different from the usual metallic brilliance. It melts at 328°C, boils at 1740°C, has a relative density of 11,4 and an atomic weight of 207,20.

It is soluble in nitric acid but not attackable by hydrochloric acid and by sulphuric acid at room temperature. It reacts slowly with water in the presence of air to form lead hydroxide, a slightly soluble compound.

There exist eight natural isotopes of lead, four of which are stable. Lead 206, 207 and 208 are respectively the final products of the decay of uranium, actinium, and thorium. Lead 204, which is also stable, hasn't natural radioactive precursors.

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