Bismuth oxychloride is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemis ...

bismuth Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

Bi O Cl. It is a lustrous white solid used since antiquity, notably in ancient Egypt. Light wave interference from its plate-like structure gives a pearly

iridescent Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfl ...

light reflectivity similar to

nacre Nacre ( , ), also known as mother of pearl, is an organicinorganic composite material produced by some molluscs as an inner shell layer; it is also the material of which pearls are composed. It is strong, resilient, and iridescent. Nacre is ...

. It is also known as pearl white.

Structure

The structure of bismuth oxychloride can be thought of as consisting of layers of , and ions (in the image Bi = grey, O = red, Cl = green). These ions are ordered as Cl–Bi–O–Bi–Cl–Cl–Bi–O–Bi–Cl, i.e., with alternating anions (, ) and cations (). The layered structure gives rise to the pearlescent properties of this material. Focusing on the coordination environment of the individual ions, the bismuth centers adopt a distorted

square antiprism In geometry, the square antiprism is the second in an infinite family of antiprisms formed by an even-numbered sequence of triangle sides closed by two polygon caps. It is also known as an ''anticube''. If all its faces are regular, it is a sem ...

atic

coordination geometry The term coordination geometry is used in a number of related fields of chemistry and solid state chemistry/physics. Molecules The coordination geometry of an atom is the geometrical pattern formed by atoms around the central atom. Inorganic coo ...

. The Bi atom is coordinated to four Cl atoms, forming one of the square faces, each at a distance of 3.06 Å from Bi, and four O atoms forming the other square face, each at a distance of 2.32 Å from Bi. The O atoms are tetrahedrally coordinated by four Bi atoms.

Synthesis and reactions

BiOCl is formed during the reaction of

bismuth chloride Bismuth chloride (or butter of bismuth) is an inorganic compound with the chemical formula BiCl3. It is a covalent compound and is the common source of the Bi3+ ion. In the gas phase and in the crystal, the species adopts a pyramidal structure, i ...

with water, i.e. the hydrolysis: : When heated above 600 °C, BiOCl converts to , called the "Arppe compound" which has a complex layer structure.

Use and occurrence

It has been used in

cosmetics Cosmetics are constituted mixtures of chemical compounds derived from either natural sources, or synthetically created ones. Cosmetics have various purposes. Those designed for personal care and skin care can be used to cleanse or protec ...

since the days of ancient Egypt. It is part of the "pearly pigment found in eye shadow, hair sprays, powders, nail polishes, and other cosmetic products".Völz, Hans G. ''et al.'' "Pigments, Inorganic" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2006 Wiley-VCH, Weinheim. . Owing to the plate-like structure of the BiOCl, its suspensions exhibit optical properties like

. In cosmetic its name is C.I. 77163. BiOCl exists in nature as the rare mineral

bismoclite Bismoclite is a bismuth oxohalide mineral with formula BiOCl. It is the naturally occurring form of bismuth oxychloride. The name was derived from its chemical constituents. It is a secondary bismuth mineral first thought to be composed of bismuth ...

, which is part of the matlockite mineral group.Bismoclite on Mindat.org
/ref> An analogous compound,

bismuth oxynitrate Bismuth oxynitrate is the name applied to a number of compounds that contain Bi3+, nitrate ions and oxide ions and which can be considered as compounds formed from Bi2O3, N2O5 and H2O. Other names for bismuth oxynitrate include bismuth subnitra ...

, is used as a white pigment.

References

{{Authority control Bismuth compounds Oxychlorides