Discovered | Found | Reactions | Uses

Gold, a transition metal in Group IB (or Group 11), is one of the most dense elements (19.3 g/cm3). Other members of the group are copper (Cu) and silver (Ag). In the solid state, the metal has a face-centered cubic structure.

Gold has been coveted by humans since prehistory, and is widely used for jewelry, electrical circuitry, and reflective coatings on windows and the Lunar Lander.

Gold is not very reactive. Unlike silver, which tarnishes when exposed to sulfur and many of its compounds, gold is the only metal that does not react with sulfur. Further, it is not affected by many acids. Only aqua regia or "kingly water", a 3:1 mixture of concentrated HCl and HNO3, will dissolve gold.

Gold! The mere thought of it has driven people to perform centuries of misguided experiments, to murder, to exploit one another, and to explore the earth. Alexander the Great invaded Persia, the Portuguese set sail into the unknown around Africa, and Columbus sailed west, all in a search for gold. The ancient alchemists made countless, fruitless attempts to synthesize gold, partly because the Greek philosopher Aristotle (384-322 BC) believed all things tend to perfection. Since gold was a model of perfection, it was a simple extension of this idea that all metals try to reach the perfect state. Thus, you find "recipes" in the writings of the alchemists such as "Take mercury, fix it with the body of Italian antimony. Cast the white earth so prepared on copper ... Add yellow electron and you will have gold." It seemed so simple - but it didn't work.

The Chinese, responsible for so many innovations in our civilization, tried to prepare gold, and it has been suggested that the word "chemistry" comes from a Chinese word meaning "gold-making juice". Gold making was important in Chinese culture not only for the lure of the metal itself but also because eating gold was said to guarantee immortality.

Gold has many uses other than its obvious one in jewelry. For example, it is a prime method payment in international commerce. Thousands of tons of bullion or gold bars lie in vaults in the Federal Reserve Bank in New York and at Fort Knox, Kentucky. In all, about 30,000 metric tons of gold bullion are stored in the U.S.

Because gold is malleable, a good electrical conductor, and does not corrode, it is used in electrical circuits of television sets, computers and calculators. But its greatest use in the U.S. is still in jewelry. In fact, more than 2.5 million school class rings containing gold are made every year.

80,000 metric tons of gold are said to have been removed from the earth in the last 6000 years. This is a staggering amount considering that the concentration of gold in the earth's crust is only about 0.004 g per million grams of earth. This means that extraordinary means have to be used to recover gold.

In ancient times gold was recovered from river sand by washing the water over a sheep's fleece, a practice that was probably the origin of the "Golden Fleece" of Greek mythology. More recently, river sand has been "panned" for gold, a method that uses the fact that gold's density is so much higher than that of sand (2.5 g/cm3). Often prospectors would find a substance that looked like gold, but was not; for example, iron pyrite is called fool's gold because it was often mistaken for gold.

As traditional sources of gold are played out, it is increasingly taken from very deep mines. The mines of South Africa, some nearly 11,000 feet deep, produce almost 2/3 of the world's gold.

After an elaborate refining process, gold is 99.95% pure and is called "24 carat" gold. Usually jewelry is not made of 24 carat gold, since it would be too soft. Instead, copper and silver are added to make it harder (and cheaper). In the U.S., jewelry is usually made from 14 carat gold that contains 14/24 or 58.33% gold.