Gold is the most familiar precious metal, but not everyone is familiar with its chemical properties and related parameters.

The elemental symbol of gold is Au, with an atomic number of 79, an atomic weight of l97, a relative density of l9.3, a melting point of 1063 ℃, a boiling point of 2860 ℃, and a valence of l or 3.

The texture of gold is very soft and has excellent ductility. It can process extremely fine silk and extremely thin sheets, so thin that they can be transparent.

Gold is extremely stable in the air, insoluble in acids, and does not react with sulfides. It is only soluble in aqua regia and alkaline solutions.

The standard electrode potential of gold is relatively positive in acidic systems, at around+1.5V (Au3+/Au), while in cyanide systems it is only 0.6V (Au2+/Au).

Gold holds an important position in the national economy, not only as a powerful backing for currency, but also as an important jewelry and decoration, and plays an important role in the electronics industry.

In order to save this valuable resource, alloys made of gold, commonly known as K-gold, are often used.

The color of pure gold is golden yellow, and the alloy color of gold becomes lighter as the gold content decreases. But the powder of gold is brown and green when it is transparent.

When electroplating gold as an alloy, various colors such as red gold, gold, cyan gold, and platinum can be obtained as the composition changes. Among the compounds of gold, gold trichloride is yellow, sodium aurate is yellow, and gold sulfide is black.

Gold plating, like silver plating, mainly uses various cyanide plating processes, but it also applies to certain cyanide free or low cyanide plating solutions, such as sulfite gold plating, citrate gold plating, etc.

Electroplating gold: divided into electroplating hard gold and water gold processes, the composition of the bath is basically the same, and the hard gold bath contains some trace metals such as nickel, cobalt, and iron.

① Purpose and function: Gold is a precious metal with characteristics such as weldability, oxidation resistance, corrosion resistance, low contact resistance, and good alloy wear resistance.

② The main method for electroplating gold on circuit boards is a citrate gold bath, which is easy to maintain and operate.

③ The gold content in water is controlled at around 1 gram/liter, with a pH value of around 4.5 and a temperature of around 35.

④ The main drugs added include acid adjustment salts, alkaline adjustment salts, conductive salts, gold plating additives, and gold salts.

⑤ After electroplating the gold plate, pure water should be used as the recycling water for washing, and it can also be used to supplement the liquid level of the evaporation change in the gold cylinder.

⑥ The gold cylinder should use platinum plated titanium mesh as the anode.

⑦ Organic pollution in the gold cylinder should be continuously filtered using carbon cores and supplemented with appropriate amounts of gold plating additives.

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