Industrial Strength Metal: Gold's practical side finds increasing applications in a variety of industries

While gold's beauty was the quality that first drew man's attention to it thousands of years ago, today, its useful qualities are making it increasingly attractive for applications ranging from the home to the hospital to outer space.

• It is unaffected by moisture, oxygen or ordinary acids
• It is biologically inactive
• It has superior electrical conductivity
• It has extraordinarily high reflective powers
• It is the most ductile and malleable of all metals.

Electronics

Gold's superior electrical conductivity, the ease with which it can be shaped and deposited on other surfaces and, most importantly, its resistance to corrosion makes it vital in contacts and connectors used in a wide range of electronic equipment - the largest industrial application of gold - to ensure accuracy and reliability.

Thin gold pastes and gold plating’s are applied to printed circuit boards in computers and to contacts for switches, relays and connectors to guarantee a dependable connection. And each year, well over two million miles of slender gold bonding wires are used in semiconductor packages.

The over 4-trillion sections of gold wire - each thinner than a human hair - that connect 40-to SO-billion tiny microprocessor chips in computers and other devices are triumphs of modern metallurgy. In 1996 alone, these connecting wires used 53 metric tons of gold (1.7 million troy ounces), worth over $544 million, yet each individual computer only needs a few cents worth to perform reliably for decades.

The number of these gold interconnections is increasing at about twelve percent a year. Because gold does not oxidise, it is the metal connection of choice between microchips and their lead frames. It possesses a lower electrical resistivity than other metals, yet has a higher melting point. Thus, gold wire will survive a higher burnout current, before failure, than aluminium, its closest competitor. Connector contacts in all miniature telephone jacks and receptacles are gold-coated, as are the switch contacts in portable cellular telephones - where use outdoors would quickly degrade other metals.

Rese archers have recently developed the world's smallest pen, capable of drawing lines as thin as 30 nanometres, or about one­ millionth of an inch. Experts expect the pen to be used for drawing nano- circuit components a thousand times smaller than today microchips. It could also be used for the precise placement and shaping of molecules of different chemicals, which act as sensors, onto microchips. This pen should make an important contribution as microchip technology becomes smaller and is based more on biology than electronics.

Medicine

Medicinal usage of gold dates back at least as far as ancient Rome, where gold sales were used in the treatment of skin ulcers. Alchemists in medieval Europe mixed powdered gold into drinks to "comfort sore limbs" - an early reference to arthritis. Gold is still used today to relieve both rheumatoid arthritis and chronic ulcers.

Its medical applications are growing. Surgeons use gold instruments to clear coronary arteries. An injection of microscopic gold pellets helps retard prostate cancer in men. Women with ovarian cancer are treated with colloidal gold. Gold-coated lasers literally give new life to patients with once inoperable heart conditions and tumours.

Because it is biologically benign, biochemists use gold to form compounds with complex material s like proteins to create new life-saving drugs. One experimental new gold compound being tested for AIDS blocks virus replication in infected cells.

Because of gold's unsurpassed ability to reflect infrared radiation, it has become an important biomedical tool for scientists studying the body's behaviour. For example, by attaching a molecular marker to a microscopic piece of gold, scientists can follow its movement through the body. And because gold is readily visible under an electron microscope, scientists can, for the first time, see whether and where a reaction takes place in an individual cell.

Some researchers are placing gold on DNA to study the hybrid genetic material in cells. Others are using it to determine how cells respond to toxins, heat and physical stress. Still, others are studying the chemical changes that occur in normally functioning cells.

One of the most promising new areas of medical research involves the use of lasers whose interior surfaces are coated with gold to control the focus of the beam. In one development, gold vapour lasers create a high-intensity reel light with the required wavelength to seek out and selectively destroy cancerous cells without harming their healthy neighbours.

A new lightweight laser designed by the military, using gold-plated contacts, enables medics to seal wounds on the battlefield and improves survival chances for the seriously wounded. In hospitals, this new design brings lasers to critically injured emergency room patients, saving precious minutes.

Satellites & Spacecraft

Gold-coated electrical connectors and contact pads provide flawless connections that ensure broadcast of static-free digital images from satellites and spacecraft, which must function unattended for years. And like the TV cameras and camcorders used at home, the satellite cameras that track weather systems or send images of other planets back to Earth depend on gold-coated wave articles to focus high-frequency signals.

Because gold is a superior reflector of heat, gold coated shielding is also used to protect delicate instruments and other spacecraft systems from intense solar radiation. Gold-coated visors also screen astronauts' eyes from damaging radiation during walks in space, a use now extended to the visors of firefighters.

In November 1996, the Mars Global Surveyor lifted off from Cape Canaveral on a ten-month voyage to Mars. Among the spacecraft's scientific payload was the Mars Orbiter Laser Altimeter. With the aid of a gold-coated parabolic telescope mirror, the altimeter will be generating extraordinarily detailed topographic maps of the entire Martian surface over a period of years.

A tracking and data relay satellite uses gold-coated Mylar to reflect intense heat from the sun.

Manufacturing

Gold-coated reflectors amplify light beams in lasers that are used in a wide range of manufacturing applications, including heat-treatment to increase the life of cylinders in locomotive diesel and to cut hard-to-work metals, like titanium, for aircraft: fuselages.

Because gold is chemically inactive, it also increases the efficiency of a number of chemical reactions. For example, because gold reduces the number of unwanted compounds created in the manufacturing process, a gold-palladium catalyst is used in the production of vinyl acetate, a building block for plastics.

And gold-coated optical fibres are gaining wide use by researchers who are studying chemical containment vessels and rocket engines that are subject to hazardous environments or high temperatures.

New research has also developed an affordable method of dyeing fabrics with gold and other precious metals to offer permanent bright colours. A chemical reduction of Free metal ions deep into the textile fibres makes the metal part of the cloth's structure. While common organic dyes bleach out when exposed to sun and chemicals, colours made by metals will remain true forever: in a test, the colour of gold-dyed silk remained unchanged after a ten-minute soak in chlorine bleach. One ounce of gold will colour roughly 380 miles of spun viscose yarn.

A tracking and data relay satellite use gold-coated Mylar to reflect intense heat from the sun.

Aircraft engines use gold brazes in the compressor section.