Please click on the products to the left for more information
READ "MSDS" SHEET BEFORE USING ANY OF OUR PRODUCTS!
Symbol
Pb (Latin plumbum, a lead weight), dense, bluish-gray metallic element
that was one of the first known metals. The atomic number of lead is 82; the
element is in group 14 (or IVa) of the periodic table
Lead
was mentioned in the Old Testament. It was used by the Romans for making water
pipes, soldered with an alloy of lead and tin.
II.
Properties
Metallic
lead is a soft, malleable, ductile metal. When gently heated it can be forced
through annular holes or dies. It has low tensile strength and is a poor
conductor of electricity. A freshly cut surface has a bright silvery luster,
which quickly turns to the dull, bluish-gray color characteristic of the metal.
Lead melts at 328° C (662° F), boils at 1740° C (3164° F), and has a
specific gravity of 11.34; the atomic weight of lead is 207.20.
Lead
is soluble in nitric acid but is little affected by sulfuric or hydrochloric
acids at room temperature. In the presence of air, it slowly reacts with water
to form lead hydroxide, which is slightly soluble. Lead is toxic when taken
internally; although ordinary water usually contains salts that form a coating
on pipes, inhibiting the formation of soluble lead hydroxide, pipes used for
carrying drinking water should not contain lead.
Lead
occurs naturally in eight isotopic forms, of which four are stable and four
radioactive. The stable isotopes, lead-206, lead-207, and lead-208, are,
respectively, the end products of the uranium, actinium, and thorium series of
radioactive decay; lead-204, also stable, has no natural radioactive
precursors
III.
Occurrence
Lead
is widely distributed all over the world in the form of its sulfide, the ore galena.
Lead ranks about 36th in natural abundance among elements in the earth's crust.
Ores of secondary importance are cerussite and anglesite. The principal method
of extracting lead from galena is to roast the ore—that is, convert it to the
oxide, and reduce the oxide with coke in a blast furnace. Another method is to
roast the ore in a reverberatory furnace until part of the lead sulfide is
converted to lead oxide and lead sulfate. The air supply to the furnace is then
cut off and the temperature raised; then the original lead sulfide combines with
the lead sulfate and lead oxide to form metallic lead and sulfur dioxide.
Waste
material, such as battery scrap, recovered from various industrial processes, is
also smelted and constitutes an important source of lead. Because galena often
has other minerals associated with it, the crude lead, or pig lead, that is
obtained from the smelting processes contains metals such as copper, zinc,
silver, and gold as impurities. The recovery of precious metals from lead ores
is often as important economically as the production of lead itself. Silver and
gold are recovered by the Parkes process, whereby a small amount of zinc stirred
into molten lead dissolves the precious metals. This molten alloy then rises to
the surface of the lead as an easily removed scum, and the zinc is removed from
the silver or gold by distillation. Pig lead is often purified by stirring
molten lead in the presence of air. The oxides of the metallic impurities rise
to the top and are skimmed off. The purest grades of lead are refined
electrolytically.
IV.
Uses
Lead
is used in enormous quantities in storage batteries and in sheathing electric
cables. Large quantities are used in industry for lining pipes, tanks, and X-ray
apparatus. Because of its high density and nuclear properties, lead is used
extensively as protective shielding for radioactive material. Among numerous
alloys containing a high percentage of lead are solder, type metal, and various
bearing metals. A considerable amount of lead is consumed in the form of its
compounds, particularly in paints and pigments.
V.
Production
Principal
sources of lead are found in Australia, the United States, Canada, Mexico, Peru,
Serbia (part of the Federal Republic of Yugoslavia), and Russia. The United
States consumes about half of the world production of lead, and it formerly
produced about one-third of the world supply. Since World War II ended in 1945,
the richest veins of galena have been exhausted, and U.S. output has been
greatly reduced.
VI.
Compounds of Lead
Basic
lead carbonate, (PbCO3) 2· Pb(OH)2, called
white lead, has been used for over 2000 years as a white pigment. It is also
used in ceramic glazes and in making other pigments. In recent years, however,
because of the dangers of lead poisoning, the use of lead-based paints for
interior use has largely been discontinued. The so-called Dutch process is the
oldest method still in use for making white lead. In this process earthenware
pots containing lead gratings and acetic acid are wrapped in tanbark (small
pieces of bark that are rich in tannin); the reaction of the fermenting tanbark
and the acetic acid is allowed to process the lead over a period of 90 days.
More rapid processes, such as electrolysis or forcing hot air and carbon dioxide
through large rotating cylinders containing powdered lead and acetic acid, are
now industrially important.
Lead
monoxide, or litharge (PbO), a yellow, crystalline powder formed by heating lead
in air, is used in making flint glass, as a drier in oils and varnishes, and in
the manufacture of insecticides. Red lead, or minium (Pb3O 4),
a scarlet, crystalline powder formed by oxidizing lead monoxide, is the pigment
in paint used as a protective coating for structural ironwork and steelwork.
Lead
chromate, or chrome yellow (PbCrO4), a crystalline powder used as a
yellow pigment, is prepared by the reaction of lead acetate and potassium
bichromate. Chrome red, orange chrome yellow, and lemon chrome yellow are some
of the pigments obtained from lead chromate. Lead acetate (Pb (C2H3
O2)2· 3H2O), a white, crystalline substance
called sugar of lead because of its sweet taste, is prepared commercially by
dissolving litharge in acetic acid. It is used as a mordant in dyeing, as a
paint and varnish drier, and in making other lead compounds. Lead tetraethyl
(Pb(C2H 5)4) is the chief constituent of the
antiknock compound added to gasoline to prevent premature detonation in
internal-combustion engines; it is considered a significant contributor to air
pollution. All gasoline-powered automobiles now manufactured in the United
States are required to operate on unleaded gasoline.
VII.
Lead Poisoning
Lead
taken internally in any of its forms is highly toxic; the effects are usually
felt after it has accumulated in the body over a period of time. The symptoms of
lead poisoning are anemia, weakness, constipation, colic, palsy, and often a
paralysis of the wrists and ankles. Flaking lead-based paints and toys made from
lead compounds are considered serious hazards for children. Children are
especially at hazard from lead, even at levels once thought safe. Lead can
reduce intelligence, delay motor development, impair memory, and cause hearing
problems and troubles in balance. In adults, one lead hazard at levels once
thought safe is that of increased blood pressure. Present-day treatment of lead
poisoning includes the administration of calcium disodium
ethylenediaminetetraacidic acid, or EDTA, a chelating agent; lead is removed
from the body by displacing the calcium in EDTA and forming a stable complex
that is excreted in the urine.
Information
from
"Lead," Microsoft® Encarta® Online Encyclopedia 2000
http://encarta.msn.com © 1997-2000 Microsoft Corporation. All rights reserved.
Lead
(Pb)
Atomic Number
82
Atomic Weight
207.2
Boiling Point
1750°C
Melting Point
327°C
Specific Gravity
11.4
Electron Configuration
Xe/4F14,5D10,6S2P
Electronegativity
2.33
Heat of Vaporization
177.7
Heat of Fusion
4.799
Electrical Conductivity
0.0481
Thermal Conductivity
0.461
Specific Heat
0.13
First Ion Potential
6.108
Covalent Radius
1.48
Atomic Radius
2.08
Atomic Volume
17.2
Oxidation States
2,