The gold is a metallic chemical element with atomic number symbol Au and 79. It is the main precious metal for mankind. In fact, according to the alchemists, it was the first noble metal known to man, influenced by the peculiarity of finding it in a metallic form and not as mineral chemical compounds, as is the case with most metals.It is bright yellow because it reflects the entire range of colors except the yellow it absorbs. Pure gold does not rust, so no oxide film will form on it. It is chemically inactive , a property that has given it a mystical meaning associated with immortality. It is not attacked by strong acids even when hot.

What is the gold for?

Gold has been known since the beginning of the Neolithic, although it is likely that it was used before. In ancient civilizations, gold was identified with the sun, due to its bright yellow color, which is why it soon received the title of “King of Metals.” The first manifestations of the use of gold are related to symbols of power and wealth.

It was so appreciated that around 3100 BC it is already recognized on crowns, thrones, chests, vessels, weapons, etc. Very often it has been used in the representation of gods and divinities, for example in the falcon head that belonged to a statue of the god Horus in the time of the Sixth Dynasty of the Old Kingdom of Egypt.

Gold is a metal that is useful for many products and activities. It serves to:

  • Make jewelry. Up to 80% of the gold produced annually is used in this area.
  • Cover statues, halls of buildings, temples and religious statues with gold leaf.
  • Glass and porcelain gilding processes.
  • Being part of electronic components of computers, telephones, calculators, televisions and missiles, for being an excellent electrical conductor.
  • In high purity, gold reflects infrared radiation (heat), which is why it serves to coat firefighters’ helmets, protecting them from high temperatures.
  • Manufacture spacesuits for astronauts, to protect both their vision and their body from high temperatures.
  • Coat spaceships to avoid excessive heating.
  • Coat telescope mirrors to capture high definition images of planets.
  • An alloy of gold, platinum and rhodium, for lining containers and pipes that house corrosive gases.
  • To form amalgams (alloy with mercury) in dentistry.
  • As gold cyanide Au (CN) 3 , it is the primary component of electrolytic baths used in the manufacture of printed circuits.
  • As gold cyanide Au (CN) 3 , it is the main component of electrolytic baths used for gilding jewelery and goldsmiths.
  • Prepare alloys and welds.
  • Manufacture high precision instruments to measure extreme temperatures.
  • Manufacture bars, plates and ingots such as the one that has the denomination of “Good Delivery”, which weighs 12.44 Kg and a minimum titer of 995 thousandths (its purity is 99.5% or greater). It is in this way that the Central Banks usually keep it, which is estimated to have more than 40,000 tons.
  • Minting gold coins.
  • Make the Olympic medals. It should be noted that these contain only six grams of pure gold, and the rest is silver .

Physical and chemical properties of gold

Gold is both a heavy metal and a noble metal. Together with silver and copper, it forms group IB of the Periodic Table of the Elements. It only has one stable isotope, mass 197. Since the 1st century it has been linked to alchemists who sought the transmutation of metals into gold and never succeeded.

The properties of gold are as follows:

  • Atomic mass: 196.97 g/mol
  • Physical state at room temperature: solid
  • Density: 19300 kg / m 3
  • Melting point: 1064 ° C
  • Boiling point: 2856 ° C
  • Specific heat: 128 J / Kg * K
  • Electrical conductivity: 4.5 * 10 7 S / m (It is one of the best electrical conductors)
  • Thermal conductivity: 317 W / K * m (It is one of the best thermal conductors)
  • It is very little reactive chemically. It does not rust and is difficult to mix with other substances, unless it is by means of alloying.
  • It can be dissolved by mixtures with oxidizing substances, such as halogens (chlorides, bromides, iodides)
  • It can be dissolved by aqua regia, which is a mixture of 3 parts of hydrochloric acid (HCl) with 1 part of nitric acid (HNO 3 )
  • Once dissolved in aqua regia, chloroauric acid is obtained, which can be transformed into metallic gold with sodium disulfite.
  • Gold becomes soluble when exposed to cyanide.

Gold and karats

According to the Metals Law, the precious metals are platinum, gold and silver. The gold that is sold is fine gold, that is, pure gold also known as: 24 karat. The carat (in the context of metals) is a unit of quality that should not be confused with the carat that is used as a unit of weight in precious stones.

Nowadays, the other measure of quality is used more, because it is more precise, which is the thousandth that is equivalent to one part of pure or fine gold per thousand of alloy . The equivalence between both units is simple: 24K equals 1000 thousandths. The gold that is usually made in jewelry is 18K, which is First Law gold, which is equivalent to 750 thousandths.

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  • Samantha Robson
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    Dr. Samantha Robson ( CRN: 0510146-5) is a nutritionist and website content reviewer related to her area of ​​expertise. With a postgraduate degree in Nutrition from The University of Arizona, she is a specialist in Sports Nutrition from Oxford University and is also a member of the International Society of Sports Nutrition.