Sodium sesquicarbonate
Encyclopedia
Sodium sesquicarbonate Na3H(CO3)2, which is a double salt
of sodium bicarbonate
and sodium carbonate
, and has a needle-like crystal
structure. However, the term is also applied to an equimolar mixture of those two salts, with whatever water of hydration the sodium carbonate includes, supplied as a powder.
The dihydrate
, Na3H(CO3)2·2H2O, occurs in nature as the evaporite
mineral
trona
.
, swimming pools and as an alkalinity
source for water treatment.
Sodium sesquicarbonate is used in the archaeological conservation of objects made of copper
and copper alloy
s that have been corroded by salt water. Treatment with sodium sesquicarbonate removes copper chloride
s from the corroded layer; if these were not removed the object would continue to corrode ("copper disease") while exposed to air.
It is also used as a precipitating
water softener, which combines with hard water minerals
(calcium
- and magnesium
-based minerals) to form an insoluble precipitate, removing these hardness minerals from the water. http://www.cleaning101.com/laundry/fact/fact_sheet4.cfm It is the carbonate moiety which forms the precipitate, the bicarbonate being included to moderate the material's alkalinity
.
Double salt
Double salts are salts containing more than one cation or anion. They form when more than one salt is dissolved in a liquid and when together they crystallize in a regular pattern. A well-known double salt is alum containing two cations and a sulfate anion...
of sodium bicarbonate
Sodium bicarbonate
Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is...
and sodium carbonate
Sodium carbonate
Sodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...
, and has a needle-like crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
structure. However, the term is also applied to an equimolar mixture of those two salts, with whatever water of hydration the sodium carbonate includes, supplied as a powder.
The dihydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
, Na3H(CO3)2·2H2O, occurs in nature as the evaporite
Evaporite
Evaporite is a name for a water-soluble mineral sediment that result from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporate deposits, marine which can also be described as ocean deposits, and non-marine which are found in standing bodies of...
mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
trona
Trona
Trona ; Na3•2H2O is an evaporite mineral. It is mined as the primary source of sodium carbonate in the United States, where it has replaced the Solvay process used in most of the rest of the world for sodium carbonate production.- Etymology :The word "trona" comes to English by way of either...
.
Uses
Sodium sesquicarbonate is used in bath saltsBath salts
The term bath salts refers to a range of water-soluble, usually inorganic solid products designed to be added to a bath. They are said to improve cleaning, improve the experience of bathing, and serve as a vehicle for cosmetic agents...
, swimming pools and as an alkalinity
Alkalinity
Alkalinity or AT measures the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. The alkalinity is equal to the stoichiometric sum of the bases in solution...
source for water treatment.
Sodium sesquicarbonate is used in the archaeological conservation of objects made of copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
and copper alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
s that have been corroded by salt water. Treatment with sodium sesquicarbonate removes copper chloride
Copper chloride
Copper forms two stable chlorides:*Copper chloride , CuCl, mineral name nantokite.*Copper chloride , CuCl2, mineral name eriochalcite....
s from the corroded layer; if these were not removed the object would continue to corrode ("copper disease") while exposed to air.
It is also used as a precipitating
Precipitation (chemistry)
Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...
water softener, which combines with hard water minerals
Hard water
Hard water is water that has high mineral content . Hard water has high concentrations of Ca2+ and Mg2+ ions. Hard water is generally not harmful to one's health but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling...
(calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
- and magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
-based minerals) to form an insoluble precipitate, removing these hardness minerals from the water. http://www.cleaning101.com/laundry/fact/fact_sheet4.cfm It is the carbonate moiety which forms the precipitate, the bicarbonate being included to moderate the material's alkalinity
Alkalinity
Alkalinity or AT measures the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. The alkalinity is equal to the stoichiometric sum of the bases in solution...
.