What Is Gold Chloride?
Gold chloride is a golden or reddish-yellow, needle-like crystal containing trivalent gold.
Gold chloride is also called tetrachloroauric(III) acid or hydrogen aurichloride. It is usually found as tetrahydrate (HAuCl4-4H2O).
Gold chloride is a highly corrosive and toxic substance. It is also designated as a deleterious substance and should be handled with care.
Uses of Gold Chloride
In addition to its use as a metal, gold chloride is widely used for decorative purposes, such as coloring ceramics, manufacturing ruby glass, gold plating, ink, and glass coloring. Other uses include the manufacture of photo-sensitive materials, medical products, reagents for alkaloids, catalysts, gold powder, gold nanoparticles, etc.
Products made with gold chloride, such as gold plating and gold nanoparticles, are characterized by their high conductivity and stability. For this reason, it is sometimes used in applications such as electrodes for electronic materials.
Properties of Gold Chloride
Gold chloride is extremely soluble in water. It is also soluble in alcohol and ether. Gold chloride, when dissolved in water, gives the tetrachloride gold (III) acid ion, [AuCl4]-. In aqueous solution, it is acidic due to hydrolysis to [AuCl3OH]-.
Gold chloride is tidally soluble and decomposes on heating to give gold (III) chloride and hydrogen chloride. Humidity should also be considered during storage and handling.
Aqueous solutions of gold chloride are orange-yellow in color. When exposed to light, aqueous solutions of gold chloride decompose to form a purple-gold colloid.
Structure of Gold Chloride
Gold chloride is a trivalent gold chloride complex with the chemical formula HAuCl4. The tetrachloride gold (III) acid ion, [AuCl4]-, in solution takes the tetracoordinate planar quadrilateral form.
Gold chloride tetrahydrate is a pale yellow needle-like crystal containing oxonium ions. The chemical formula is H3O+AuCl4-・3H2O.
The molar mass of anhydrous gold chloride is 339.785 g/mol, while the molar mass of tetrahydrate is 411.85 g/mol. The density of tetrahydrate is 3.9 g/cm3.
Other Information on Gold Chloride
1. Synthesis and Reaction of Gold Chloride
Gold chloride is produced by dissolving gold in royal water or by reacting gold with chlorine in hydrochloric acid. Evaporation precipitation of this aqueous solution will yield tetrahydrate.
When heated, gold chloride decomposes into chlorine (Cl2), hydrogen chloride (HCl), and gold (Au). Specifically, when heated, it decomposes via AuCl3 and AuCl, and when heated strongly, chlorine is generated and Au remains.
2. Characteristics of Gold Chloride
Sodium gold chloride and potassium gold chloride are examples of gold chloride salts. Other known examples include alkaline earth metal salts, ammonium salts (NH4), cobalt salts (Co), and nickel salts (Ni).
3. Characteristics of Sodium Gold Chloride
The chemical formula for the salt of gold chloride and sodium is Na[AuCl4]. Sodium gold chloride is also called gold salt. Ordinary sodium gold chloride is dihydrate. It is formed when sodium chloride (NaCl) is added to a solution of HAuCl4 produced by dissolving gold in royal water.
Sodium gold chloride dihydrate is a yellow orthorhombic crystal containing planar square [AuCl4]-. The gold-chlorine bond (Au-Cl) distance is approximately 2.28 Å. Sodium gold chloride is soluble in water.
When heated, it loses Cl2 to give Na[AuCl2]. Sodium gold chloride is used as a raw material for the production of other gold compounds as well as for coloring photographs, ceramics, glass, and electrolytic gold plating solutions. Potassium gold chloride is another salt with similar properties to sodium gold chloride.
4. Hazards of Gold Chloride
Gold chloride, when inhaled, irritates the mucous membranes of the nose, throat, and bronchi. Gold chloride in contact with the skin will leave red spots on the skin, and when gold chloride enters the eyes, it can severely irritate the mucous membranes.
In addition to this, inorganic gold salts are relatively dangerous because of their strong oxidizing and corrosive properties.