Metals
PEW 106
Platinum
Platinum is a beautiful silvery-white metal, when
pure, and is malleable and ductile. It has a
coefficient of expansion almost equal to that of
soda-lime-silica glass, and is therefore used to
make sealed electrodes in glass systems.
The metal does not oxidise in air. It is insoluble in
hydrochloric and nitric acid, but dissolves when
they are mixed as aqua regia, forming
chloroplatinic acid (H2PtCl6), an important
compound. It is corroded by halogens, cyanides,
sulphur and alkalis. Hydrogen and oxygen gas
mixtures explode in the presence of platinum wire.
Gold
Gold is usually alloyed in jewellery to give it more
strength, and the term carat describes the amount
of gold present (24 carats is pure gold). It is
estimated that all the gold in the world, so far
refined, could be placed in a single cube 60 ft. on a
side. It is metallic, with a yellow colour when in a
mass, but when finely divided it may be black,
ruby, or purple.
It is the most malleable and ductile metal; 1 ounce
(28 g) of gold can be beaten out to 300 square
feet. It is a soft metal and is usually alloyed to give
it more strength. It is a good conductor of heat and
electricity, and is unaffected by air and most
Graphite (form of carbon)
Carbon is found free in nature in three allotropic forms:
amorphous, graphite, and diamond. A fourth form, known as
"white" carbon, is now thought to exist. Ceraphite is one of
the softest known materials while diamond is one of the
hardest. Graphite exists in two forms: alpha and beta. These
have identical physical properties, except for their crystal
structure. Naturally occurring graphites are reported to
contain as much as 30% of the rhombohedral (beta) form,
whereas synthetic materials contain only the alpha form. The
hexagonal alpha type can be converted to the beta by
mechanical treatment, and the beta form reverts to the alpha
on heating it above 1000C.
Titanium
Titanium minerals are quite common. The metal
has a low density, good strength, is easily
fabricated, and has excellent corrosion resistance.
The metal burns in air and is the only element that
burns in nitrogen. It is marvellous in fireworks.
Silver
Silver is somewhat rare and expensive, although
not as expensive as gold. Pure silver has a brilliant
white metallic lustre. It is a little harder than gold
and is very ductile and malleable. Pure silver has
the highest electrical and thermal conductivity of
all metals, and possesses the lowest contact
resistance. Silver iodide, AgI, is (or was?) used for
causing clouds to produce rain.
Silver is stable in pure air and water, but tarnishes
when exposed to ozone, hydrogen sulphide, or air
containing sulphur. It occurs in ores including
argentite, lead, lead-zinc, copper and gold found in
Mexico, Peru, and the USA.
Nickel
Nickel is found as a constituent in most
meteorites and often serves as one of the criteria
for distinguishing a meteorite from other
minerals. Iron meteorites, or siderites, may
contain iron alloyed with from 5 to nearly 20%
nickel. The USA 5-cent coin (whose nickname is
"nickel") contains just 25% nickel. Nickel is a
silvery white metal that takes on a high polish. It
is hard, malleable, ductile, somewhat
ferromagnetic, and a fair conductor of heat and
electricity.
Molybdenum
Molybdenum is a silvery-white, hard, transition
metal. Scheele discovered it in 1778. It was often
confused with graphite and lead ore. Molybdenum
is used in alloys, electrodes and catalysts. The
World War 2 German artillery piece called "Big
Bertha" contains molybdenum as an essential
component of its steel.
valuable alloying agent (contributes to the
hardenability and toughness of quenched and
tempered steels). Almost all ultra-high strength
steels contain molybdenum in amounts from 0.25
to 8%
Chromium
Chromium is steel-gray, lustrous, hard, metallic,
and takes a high polish. Its compounds are toxic. It
is found as chromite ore. Siberian red lead
(crocoite, PrCrO4) is a chromium ore prized as a red
pigment for oil paints.
Used to harden steel, to manufacture stainless
steel, and to form alloys
Used in plating to produce a hard, beautiful surface
and to prevent corrosion.
INCONEL 600 ®
Alloy 600 is a nickel-chromium alloy designed for
use from cryogenic to elevated temperatures in
the range of 2000 deg F(1093 deg C). The high
nickel content of the alloy enables it to retain
considerable resistance under reducing conditions
and makes it resistant to corrosion by a number
of organic and inorganic compounds. The nickel
content gives it excellent resistance to chloride-
ion stress-corrosion cracking and also provides
excellent resistance to alkaline solutions.
MONEL 400 ®
A Nickel-Copper alloy, resistant to sea water and steam
at high temperatures as well as to salt and caustic
solutions.
Alloy 400 is a nickel-copper alloy with excellent corrosion
resistance in a wide variety of media. The alloy is
characterized by good general corrosion resistance, good
weldability and moderate to high strength. The alloy has
been used in a variety of applications. It has excellent
resistance to rapidly flowing brackish water or seawater. It
is particularly resistant to hydrochloric and hydrofluoric
acids when they are de-aerated. The alloy is slightly
magnetic at room temperature. The alloy is widely used in
the chemical, oil and marine industries.
Copper
Copper is one of the most important metals.
Copper is reddish with a bright metallic lustre. It
is malleable, ductile, and a good conductor of
heat and electricity (second only to silver in
electrical conductivity). Its alloys, brass and
bronze, are very important. The most important
compounds are the oxide and the sulphate, (blue
vitriol).
Tin
Ordinary tin is a silvery-white metal, is malleable,
somewhat ductile, and has a highly crystalline
structure. Due to the breaking of these crystals, a
"tin cry" is heard when a bar is bent. The element
has two allotropic forms. On warming, grey, or -
tin, with a cubic structure, changes at 13.2°C into
white, or -tin, the ordinary form of the metal.
White tin has a tetragonal structure. When tin is
cooled below 13.2°C, it changes slowly from white
to grey. This change is affected by impurities such
as aluminium and zinc, and can be prevented by
small additions of antimony or bismuth.
Used to coat other metals to prevent corrosion or
other chemical action (tin cans are made from tin
Lead
Lead is a bluish-white lustrous metal. It is very
soft, highly malleable, ductile, and a relatively
poor conductor of electricity. It is very resistant to
corrosion but tarnishes upon exposure to air.
Lead pipes bearing the insignia of Roman
emperors, used as drains from the baths, are still
in service. Alloys include pewter and solder.
Tetraethyl lead (PbEt4) is still used in some
grades of petrol (gasoline) but is being phased
out on environmental grounds.
Aluminum
Pure aluminium is a silvery-white metal with many
desirable characteristics. It is light, nontoxic (as
the metal), nonmagnetic and nonsparking. It is
somewhat decorative. It is easily formed,
machined, and cast. Pure aluminium is soft and
lacks strength, but alloys with small amounts of
copper, magnesium, silicon, manganese, and
other elements have very useful properties.
Aluminium is an abundant element in the earth's
crust, but it is not found free in nature. The Bayer
process is used to refine aluminium from bauxite,
an aluminium ore.
Cadmium
Cadmium is a soft, bluish-white metal and is
easily cut with a knife. It is similar in many
respects to zinc. Interestingly, aa characteristic
cadmium "scream" is heard on bending a
cadmium bar (such as that illustrated above).
Cadmium and its compounds are highly toxic.
Silver solder, which contains cadmium, should be
handled with care.
Rather like zinc, cadmium is used to a small
extent as coatings (often achieved by
electroplating) to protect metals such as iron. Its
use is restricted because of environmental
concerns. Cadmium is a component of Ni-Cd
batteries.
Zinc
Zinc is a bluish-white, lustrous metal. It is brittle
at ambient temperatures but is malleable at 100
to 150°C. It is a reasonable conductor of
electricity, and burns in air at high red heat with
evolution of white clouds of the oxide.
A large proportion of all zinc, perhaps more than
a third, is used used to galvanize metals such as
iron so as to prevent corrosion. Typically this
involves dipping the object to be coated in
molten zinc for a short time but electroplating or
paining methods are also used.
Magnesium
Magnesium is a grayish-white, fairly tough metal.
Magnesium is the eighth most abundant element
in the earth's crust although not found in it's
elemental form. Magnesium tarnishes slightly in
air, and finely divided magnesium readily ignites
upon heating in air and burns with a dazzling white
flame. Normally magnesium is coated with a layer
of oxide, MgO, that protects magnesium from air
and water. it is lighter than aluminium, and is used
in alloys used for aircraft, car engine casings,
