Uses
The metal is obtained
mainly by electrolysis of fused calcium chloride, an expensive
process. Until recently the pure metal had little use in industry. It is
being used to a larger extent as a deoxidizer for copper, nickel, and stainless
steel. Because calcium hardens lead when alloyed with it, lead-calcium alloys
are excellent for bearings, superior to ordinary lead antimony for grids in
storage batteries, and more durable as sheathing for lead-covered cable. Calcium
is present in the chemically combined state in lime (calcium hydroxide), cement
and mortar (as calcium hydroxide or a variety of silicates of calcium), bones
and teeth (as a calcium hydroxyphosphate), and in many body fluids (as complex
proteinaceous compounds) essential to muscle contraction, the transmission of
nerve impulses, and the clotting of blood.
Uses
Magnesium forms divalent
compounds, primarily among which are magnesium carbonate (MgCO3),
which is formed by the reaction of a magnesium salt and sodium carbonate and is
used as a refractory and insulating material; magnesium chloride (MgCl2·6H2O),
which is formed by reacting magnesium carbonate or oxide with hydrochloric acid
and is used as dressing and filler for cotton and woollen fabrics, in the
manufacturing of paper, and in cements and ceramics; magnesium citrate
(Mg3(C6H
5O7)2·4H2O),
which is formed by the reaction of magnesium carbonate with citric acid and is
used in medicine and effervescent beverages; magnesium hydroxide (Mg(OH)2),
formed by the reacting of magnesium salt and sodium hydroxide and used in
medicine as the laxative “milk of magnesia”, and in sugar refining;
magnesium sulphate (MgSO4·7H2O),
well known as Epsom salt; and magnesium oxide (MgO), called burnt magnesia, or
magnesia, prepared by burning magnesium in oxygen or by heating magnesium
carbonate and used as a heat-refractory and insulating material, in cosmetics,
as a filler in paper manufacture, and as a mild, antacid laxative.
Alloyed forms of
magnesium have considerable tensile strength. The metal is used when lightness
is an key factor: alloyed with aluminium or copper, it is used extensively in
making castings for aeroplane parts; in artificial limbs, vacuum cleaners, and
optical instruments; and in such products as skis, wheelbarrows, lawn mowers,
and outdoor furniture. The unalloyed metal is used in incendiary bombs,
photographic flash powders, and signal flares; as a deoxidizer in the casting of
metals; and as a getter, a substance
that achieves final evacuation in vacuum tubes.
The estimated world
production of magnesium in 1989 was 350,000 metric tons.
Uses
A given volume of
aluminium weighs less than one-third as much as the same volume of steel. The
only lighter metals are lithium, beryllium, and magnesium. Its high
strength-to-weight ratio makes aluminium effective in the construction of
aircraft, railway carriages, and motor vehicles, and for other applications in
which mobility and energy conservation are important. Because of its high heat
conductivity, aluminium is used in cooking utensils and the pistons of
internal-combustion engines. Aluminium has only 63 per cent of the electrical
conductance of copper for wire of a given size, but it weighs less than half as
much. An aluminium wire of comparable conductance to a copper wire is thicker
but still lighter than the copper. Weight is particularly important in
long-distance, high-voltage power transmission, and aluminium conductors are now
used to transmit electricity at 700,000 volts or more.
The metal is becoming
increasingly important architecturally, for both structural and ornamental
purposes. Aluminium siding, storm windows, and foil make excellent insulators.
The metal is also used as a material in low-temperature nuclear reactors because
it absorbs relatively few neutrons. Aluminium becomes stronger and retains its
toughness as it gets colder and is therefore used at cryogenic temperatures.
Aluminium foil 0.018 cm (0.007 in) thick, now a common household convenience,
protects food and other perishable items from spoilage. Because of its light
weight, ease of forming, and compatibility with foods and beverages, aluminium
is widely used for containers, flexible packages, and easy-to-open bottles and
cans. The recycling of such containers is an increasingly important
energy-conservation measure. Aluminium's resistance to corrosion in salt water
also makes it beneficial in boat hulls and various marine devices.
A wide variety of
coating alloys and wrought alloys can be prepared that give the metal greater
strength, or resistance to corrosion or high temperatures. Some new alloys can
be used as armour plate for tanks, personnel carriers, and other military
vehicles.
Uses
The metal is used mainly
as a protective coating, or galvanizer, for iron and steel; as an ingredient of
various alloys, especially brass; as plates for dry electric cells; and for die
castings. Zinc oxide, known as zinc white or Chinese white, is used as a paint
pigment. It is also used as a filler in rubber tyres and is employed in medicine
as an antiseptic ointment. Zinc chloride is used as a wood preservative and as a
soldering fluid. Zinc sulphide is useful in applications involving
electroluminescence, photoconductivity, and semiconductivity and has other
electronic uses. It is employed as a phosphor for the screens of television
tubes and in fluorescent coatings.
Uses
and Production
Pure iron, prepared by
the electrolysis of ferrous sulphate solution, has restricted use. Commercial
iron always contains small amounts of carbon and other impurities that alter its
physical properties, which are considerably improved by the further addition of
carbon and other alloying elements.
By far the largest
amount of iron is used in processed forms, such as wrought iron, cast iron, and
steel. Commercially pure iron is used for the production of galvanized sheet
metal and of electromagnets. Iron compounds are employed for medicinal purposes
in the treatment of anaemia, when the amount of haemoglobin or the number of red
blood corpuscles in the blood is lowered. Iron is also used in tonics.
In the early 1990s,
annual world production was nearly 920 million metric tons.
Compounds
Iron forms compounds in
which it has a valence of +2 (formerly ferrous compounds) and compounds in which
it has a valence of +3 (formerly ferric compounds). Iron(II) compounds are
easily oxidized to iron(III) compounds. The most important iron(II) compound is
iron(II) sulphate (FeSO4), called
green vitriol or copperas; it usually occurs as pale-green crystals containing
seven molecules of water of hydration. It is obtained in large quantities as a
by-product in pickling iron and is used as a mordant in dyeing, as a tonic
medicine, and in the making of ink and pigments.
Iron(III) oxide, an
amorphous red powder, is obtained by treating iron(III) salts with a base or by
oxidizing pyrite. It is used both as a pigment, known as either iron red or
Venetian red; as a polishing abrasive, known as rouge; and as the magnetizable
medium on magnetic tapes and disks. Iron(III) chloride, obtained as dark-green,
shiny crystals by heating iron in chlorine, is used in medicine as an alcoholic
solution called tincture of iron.
The iron(II) and
iron(III) ions combine with cyanides to form complex cyanide compounds. Iron(III)
hexacyanoferrate(II) , or ferric ferrocyanide (Fe4[Fe(CN)6]3),
a dark-blue, amorphous solid formed by the reaction of potassium
hexacyanoferrate(II) with an iron(III) salt, is called Prussian blue. It is used
as a pigment in paint and in laundry bluing to correct the yellowish tint left
by the iron(II) salts in water. Potassium hexacyanoferrate(III) (K3Fe(CN)6),
called red prussiate of potash, is obtained from iron(II) hexacyanoferrate(III)
(Fe3[Fe(CN)6]2;
also called Turnbull's blue), and is used in processing blueprint paper. Iron
also undergoes physiochemical reactions with carbon that are necessary to the
formation of steel.
Properties
and Uses
Copper melts at about
1083° C (about 1981° F), boils at about 2567° C (about 4753° F), and has a
relative density of 8.9. The atomic weight of copper is 63.846.
Because of its many
desirable properties, such as its conductivity of electricity and heat, its
resistance to corrosion, its malleability and ductility, and its beauty, copper
has long been used in a wide variety of applications. The main uses are
electrical, because of copper's extremely high conductivity, which is second
only to that of silver. Because copper is very ductile, it can be drawn into
wires of any diameter from about 0.025 mm (about 0.001 in) upwards. The tensile
strength of drawn copper wire is about 4200 kg/sq cm (about 60,000 lb/sq in); it
can be used in outdoor power lines and cables, as well as in house wiring, lamp
cords, and electrical machinery such as generators, motors, controllers,
signalling devices, electromagnets, and communications equipment.
Copper has been used for coins throughout recorded history and has also been fashioned into cooking impliments, vats, and ornamental objects. Copper was once used in large amounts for sheathing the bottom of wooden ships to prevent fouling. Copper can easily be electroplated, alone or as a base for other metals. Large amounts are used for this purpose, particularly in making electrotypes, reproductions of type for printing.
The metallurgy of copper
varies with the composition of the ore. Native copper is crushed, washed, and
cast in bars. Oxides and carbonates are reduced with carbon. The most important
ores, the sulphides, contain not more than 12 per cent, sometimes as little as 1
per cent, of copper; they must first be crushed and concentrated by flotation.
The concentrates are smelted in a reverberatory furnace, which yields crude
metallic copper, approximately 98 per cent pure. Crude copper is further
purified by electrolysis, yielding bars exceeding 99.9 per cent purity.
Pure copper is soft but
can be made stronger or tougher somewhat by being worked. Alloys of copper,
which are far harder and stronger than the pure metal, have higher resistance
and so cannot be used for electrical purposes. They do, however, have corrosion
resistance almost as good as that of pure copper and are very easily worked in
machine shops. The two most important alloys are brass, a zinc alloy, and
bronze, a tin alloy. Both tin and zinc are sometimes added to the same alloy,
and no sharp dividing line can be drawn between brass and bronze. Both are used
in enormous quantities. Copper is also alloyed with gold, silver, and nickel,
and is an important constituent of such alloys as Monel metal, gunmetal, and
German silver.
Copper forms two series
of chemical compounds: cuprous, in
which the copper has a valence of 1, and cupric,
in which the copper has a valence of 2. Cuprous compounds are easily oxidized to
cupric, in many cases by mere exposure to air, and are of little industrial
importance; cupric compounds are stable. Certain copper solutions have the power
of dissolving cellulose, and large amounts of copper are for this reason used in
the manufacture of rayon. Copper is also used in many pigments and in such
insecticides as Paris green and such fungicides as Bordeaux mixture, although it
is being largely replaced by synthetic organic chemicals for these purposes.
Uses
Lead is used in huge
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 other bearing metals. A
considerable amount of lead is consumed in the form of its compounds,
particularly in paints and pigments.
Compounds
of Lead
Basic lead carbonate,
(PbCO3)2 · Pb(OH)2, called
white lead, has been used for over 2,000 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 abandoned. 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 ethanoic acid are wrapped in tanbark (small
pieces of bark that are rich in tannin); the reaction of the fermenting tanbark
and the ethanoic 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 ethanoic 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 (Pb3O4), 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(II) ethanoate (Pb (C2H3O2)2
· 3H2O), a white, crystalline
substance called sugar of lead because of its sweet taste, is prepared
commercially by dissolving litharge in ethanoic acid. It is used as a mordant in
dyeing, as a paint and varnish drier, and in making other lead compounds.
Lead(IV) tetraethyl (Pb(C2H5)4)
is the main constituent of the antiknock compound added to petrol to prevent
premature detonation in internal-combustion engines; it is considered a
significant contributor to air pollution.
NaCl (Salt)
The most common use of
salt is as a seasoning. Salt is an essential constituent in the diet of human
beings and other warm-blooded animals. Certain peoples restrict the consumption
of salt, but they obtain necessary quantities of it by eating salt-containing
raw or cooked meat and fish. Common table salt marketed for consumption in
inland areas often has small quantities of iodides added to prevent the
occurrence of goitre. Wild animals often congregate at salt streams or surface
encrustations of salt, called salt licks,
where they lick the salt deposits.
Industrially, salt is the source of chlorine and its main compounds and the source of sodium and its compounds. Chlorine compounds of commercial importance include hydrochloric acid, chloroform, carbon tetrachloride, and bleaching powder. Important sodium compounds include sodium carbonate , sodium sulphate, baking soda, sodium phosphate, and sodium hydroxide. Salt is used on a large scale as a preservative for meats and is employed in some refrigeration processes, in dyeing, and in the manufacture of soap and glass. Because they are transparent to infrared radiation, salt crystals are used for making the prisms and lenses of instruments used in the study of infrared radiation.
Soda, term applied to
various compounds of sodium, and particularly to sodium carbonate (Na2CO3),
and sodium bicarbonate (NaHCO3).
Sodium carbonate, which has a relative density of 2.53 and a melting point of
851° C (1563.8° F), is a white powder with strong alkaline properties; it
occurs naturally dissolved in the waters of inland lakes called soda
lakes. It is also found in some salt beds. Several hydrated forms of sodium
carbonate are manufactured, chief among which are the decahydrate (Na2CO3
· 10H2O), called washing
soda or sal soda, and the
monohydrate (Na2CO3
· H2O), called crystal carbonate.
Sodium carbonate was
first prepared from the ashes of seaweed and was called soda ash, but it was not used on a large scale until the French
chemist Nicolas Leblanc devised a method, called the Leblanc process, for the production of the compound from ordinary
table salt, sodium chloride. The Leblanc process was substituted by the less
expensive Solvay process, invented by
the Belgian chemist Ernest Solvay, in an attempt to use the ammonia obtained as
a by-product in the coke industry. In the Solvay process, sodium chloride is
treated with ammonia gas and then with carbon dioxide, resulting in the
production of sodium bicarbonate (NaHCO3),
and ammonium chloride. The sodium bicarbonate precipitate is filtered from the
solution of ammonium chloride and is dried and heated to form sodium carbonate.
Increasingly, however, rather than using synthetic processes such as the Solvay
process, sodium carbonate is being obtained from natural sources, such as soda
lakes.
Sodium carbonate is used
in the manufacture of glass and ceramics, in the pulping of wood to make paper,
and in the manufacture of soap. It is also used in petroleum refining, as a
water softener, as a cleaner and degreaser in washing compounds, and in the
manufacture of other sodium-containing compounds, such as sodium hydroxide.
Sodium bicarbonate, or baking
soda, is a white powder with a relative density of 2.16. It decomposes when
heated in air above 55° C (131° F), losing carbon dioxide and water and
forming sodium carbonate. It is an important constituent of baking powder and is
also employed as a source of carbon dioxide in fire extinguishers. It is used
medicinally to neutralize excessive acid in the stomach and industrially to
moderate the alkalinity of sodium carbonate. It occurs naturally in many mineral
springs and is manufactured by treating sodium carbonate with water and carbon
dioxide.
Limestone, common type
of sedimentary rock composed mainly of calcite (calcium carbonate, CaCO3).
When “burned” or calcined (raised to a high temperature), it yields lime
(calcium oxide, CaO). Crystalline metamorphosed limestone is known as marble.
Many varieties of limestone are formed by the consolidation of sea shells, which
are formed by the largely CaCO3
secretions of various marine animals. Chalk is a variety of porous, fine-grained
limestone composed mostly of foraminifera shells; coquina is a soft limestone
made up of shell fragments. A variety of the rock, known as oölitic limestone,
is composed of small egg-shaped concretions, each containing a nucleus of a sand
grain or other different particle around which deposition has taken place. Some
types of limestone, such as Portland stone, are used in building.
Chalk, soft white or
whitish form of limestone composed of the remains of small marine organisms such
as foraminifera and coccoliths. Chemically it is almost pure calcium carbonate
with traces of other minerals. It varies in hardness and texture from very soft
porous varieties to harder close-grained types. Chalk is particularly common in
strata of the Cretaceous period (Lat., creta, “chalk”). Large deposits are found in Iowa, Texas, and
Arkansas, and in the downlands of southern England. Cretaceous chalk is exposed
in the White Cliffs of Dover on the coast of the English Channel.
Gypsum, common mineral
consisting of hydrated calcium sulphate (CaSO4·2H2O).
It is a largely distributed form of sedimentary rock, formed by the
precipitation of calcium sulphate from seawater, and is frequently associated
with other saline deposits, such as halite and anhydrite, as well as with
limestone and shale. Gypsum is produced in volcanic regions by the action of
sulphuric acid on calcium-containing minerals; it is also found in most clays as
a product of the action of sulphuric acid on limestone. It occurs in all parts
of the world; some of the best workable deposits are in France, Switzerland, the
United States, and Mexico. Alabaster, selenite, and satin spar are varieties of
gypsum.
Artificial gypsum is
obtained as a by-product in an old method for the manufacture of phosphoric
acid. Rock phosphate, the essential constituent of which is tricalcium
phosphate, is treated with sulphuric acid, producing phosphoric acid and gypsum.
The gypsum is compacted into blocks and used for the construction of
non-supporting walls in buildings. By properly controlling the concentration and
temperature of sulphuric acid added to phosphate rock, a mixture of monocalcium
phosphate, dicalcium phosphate, and gypsum may be obtained. This mixture is a
valuable fertilizer, known as superphosphate.
Gypsum crystallizes in
the monoclinic system in white or colourless crystals, which are massive or
foliated in formation. Many specimens are coloured green, yellow, or black by
impurities. With a hardness ranging from 1.5 to 2, it is soft enough to scratch
with a fingernail and has a relative density of 2.3. When heated to 128° C
(262.4° F), it loses part of its water of crystallisation and is converted into
plaster of Paris, CaSO4 · 1H2O.
Finely ground plaster of Paris, when mixed to a paste with water, sets in a
short time into a hard mass of gypsum, the rehydrated crystals forming and
interlocking in such a way as to cause expansion in volume.
Because of its property
of swelling and filling all small spaces on drying, plaster of Paris is used
extensively in making casts for statuary, ceramics, dental plates, fine metal
parts for precision instruments, and surgical splints. Uncalcined gypsum is used
as a fertilizer for dry, alkaline soil. It is also used as a bed for polishing
plate glass and as a basis for paint pigments. Large amounts of gypsum are used
as a retarder in portland cement.
I
COULD NOT FIND ANYTHING ON Ca(OH)2
or Al(OH)3
Will add this Shortly [F.S]
Chemistry Department: Loreto College, Coleraine.