Gold(III) oxide
Encyclopedia
Gold oxide (Au2O3) is the most stable oxide
of gold
. It is a red-brown, thermally unstable solid that decomposes at 160 °C. The hydrated form is weakly acidic
and dissolves in concentrated alkali
to form salts that are believed to contain the [Au(OH)4]− ion.
Anhydrous AuO can be prepared by heating amorphous hydrated gold(III) oxide with perchloric acid
and an alkali metal
perchlorate
in a sealed quartz
tube at a temperature of around 250 °C and a pressure of around 30 MPa.
Gold oxide is used to make highly-valued cranberry or red-colored glass, which, like colloidal
gold suspensions, contains evenly-sized spherical gold nanoparticles
.
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
of gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
. It is a red-brown, thermally unstable solid that decomposes at 160 °C. The hydrated form is weakly acidic
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
and dissolves in concentrated alkali
Alkali
In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...
to form salts that are believed to contain the [Au(OH)4]
Anhydrous AuO can be prepared by heating amorphous hydrated gold(III) oxide with perchloric acid
Perchloric acid
Perchloric acid is the inorganic compound with the formula HClO4. Usually encountered as an aqueous solution, this colourless compound is a strong acid comparable in strength to sulfuric and nitric acids. It is a powerful oxidizer, but its aqueous solutions up to appr. 70% are remarkably inert,...
and an alkali metal
Alkali metal
The alkali metals are a series of chemical elements in the periodic table. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, along with hydrogen. The alkali metals are lithium , sodium , potassium , rubidium , caesium , and francium...
perchlorate
Perchlorate
Perchlorates are the salts derived from perchloric acid . They occur both naturally and through manufacturing. They have been used as a medicine for more than 50 years to treat thyroid gland disorders. They are used extensively within the pyrotechnics industry, and ammonium perchlorate is also a...
in a sealed quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
tube at a temperature of around 250 °C and a pressure of around 30 MPa.
Gold oxide is used to make highly-valued cranberry or red-colored glass, which, like colloidal
Colloid
A colloid is a substance microscopically dispersed evenly throughout another substance.A colloidal system consists of two separate phases: a dispersed phase and a continuous phase . A colloidal system may be solid, liquid, or gaseous.Many familiar substances are colloids, as shown in the chart below...
gold suspensions, contains evenly-sized spherical gold nanoparticles
Nanoparticle
In nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size : in terms of diameter, coarse particles cover a range between 10,000 and 2,500 nanometers. Fine particles are sized...
.