ABOUT LEAD
Name
: Lead (Latin: plumbum)
Symbol : Pb
Boling Point : about 1,740°C
Melting Point : 327.5°C
Color : bluish white
Density of solid [/kg m-3] : 11340 at 20oC
Classification : Metallic
Solubility : Insoluble in water
Atomic Number : 82
Atomic Weight : 207.2 (1) g m
Conditions to Avoid : Heat, flames, ignition sources and
incompatibles
Stability : Stable under ordinary conditions of use and storage
Lead
is a relatively soft metal with bluish-white lusture but on exposure to
air, it becomes covered by a dull, gray layer of basic carbonate that
adheres closely and protects it from further oxidation or corrosion. It
has a low tensile strength and a relatively poor conductor of
electricity. It has a face-centered cubic crystalline structure. Native
Lead rarely occurs in nature. It is usually associated with ore with Zn,
Ag and Cu, and is extracted together with these metals. The Lead metal
is primarily extracted from sulphide ore i.e galena (PbS), which has the
86.6% Lead content. two other minerals commercially mined for Lead are cerussite (PbCO3) and anglesite (PbSO4). Over 95% of all Lead mined is
derived from one of these three minerals. The largest source of Lead,
however, is from recycling, & the automobile battery takes the lion’s
share.
Lead
has the advantages of low melting temperature(327o C) and good
malleability, which enable Lead articles to be cast, join & shape
easily. The very high density of Lead makes it suitable for shielding
against sound, vibrations and radiation, for example as protection for
users of computer and TV screens. For these purposes Lead is used in
metallic form or as Lead compounds in Lead glasses. Some compounds of
Lead have their own useful properties, particularly in relation to color
and glass-forming ability.
Modern
Lead mines produce about 3 million metric tons of Lead annually. This is
only about half the Lead used worldwide; the remainder is obtained by
recycling. The top producer of Lead is Australia, followed by the United
States, China, and Canada. Other countries with major Lead deposits are
Mexico, Peru, Russia, and Kazakhstan. |