Strontium chloride
Encyclopedia
Strontium chloride is a salt
of strontium
and chloride
. It is a typical salt
, forming neutral
aqueous solutions. Like all compounds of Sr, this salt emits a bright red colour in a flame; in fact is used as a source of redness in fireworks. Its chemical properties are intermediate between those for barium chloride
, which is more toxic, and calcium chloride
.
or strontium carbonate
with hydrochloric acid
:
Crystallization from cold aqueous solution gives the hexahydrate
, SrCl2·6H2O. Dehydration of this salt occurs in stages, commencing above 61 °C. Full dehydration occurs at 320 °C.
structure. In the vapour phase the SrCl2 molecule is non-linear with a Cl-Sr-Cl angle of approximately 130°. This is an exception to VSEPR theory which would predict a linear structure. Ab initio calculations have been cited to propose that contributions from d orbitals in the shell below the valence shell are responsible. Another proposal is that polarisation of the electron core of the strontium atom causes a distortion of the core electron density that interacts with the Sr-Cl bonds.
to other compounds of strontium, such as yellow strontium chromate, which is used as a corrosion inhibitor for aluminium
. The precipitation proceeds analogously to the related, isostructural sulfate:
Strontium chloride is often used as a red colouring agent in pyrotechnics
. It imparts a much more intense red colour to the flames than most other alternatives. It is employed in small quantities in glass
-making and metallurgy
. The radioactive isotope
strontium-89, used for the treatment of bone cancer, is usually administered in the form of strontium chloride. Sea water aquaria
require small amounts of strontium chloride, which is consumed in the production of the exoskeleton
s of certain plankton
.
containing nerve endings that have become exposed by gum recession. Known in the US as Elecol and Sensodyne
, these products are called "strontium chloride toothpastes", although most now use potassium nitrate
instead which works as a nerve calming agent rather than a barrier.http://www.sensodyne.co.uk/how_it_works.htm
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
of strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
and chloride
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
. It is a typical salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
, forming neutral
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
aqueous solutions. Like all compounds of Sr, this salt emits a bright red colour in a flame; in fact is used as a source of redness in fireworks. Its chemical properties are intermediate between those for barium chloride
Barium chloride
Barium chloride is the inorganic compound with the formula BaCl2. It is one of the most common water-soluble salts of barium. Like other barium salts, it is toxic and imparts a yellow-green coloration to a flame. It is also hygroscopic....
, which is more toxic, and calcium chloride
Calcium chloride
Calcium chloride, CaCl2, is a salt of calcium and chlorine. It behaves as a typical ionic halide, and is solid at room temperature. Common applications include brine for refrigeration plants, ice and dust control on roads, and desiccation...
.
Preparation
Strontium chloride can be prepared by treating strontium hydroxideStrontium hydroxide
Strontium hydroxide, Sr2, is a caustic alkali composed of one strontium ion and two hydroxide ions. It is synthesized by combining a strontium salt with a strong base...
or strontium carbonate
Strontium carbonate
Strontium carbonate is the carbonate salt of strontium that has the appearance of a white or grey powder. It occurs in nature as the mineral strontianite.- Chemical properties :...
with hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
:
- Sr(OH)2Strontium hydroxideStrontium hydroxide, Sr2, is a caustic alkali composed of one strontium ion and two hydroxide ions. It is synthesized by combining a strontium salt with a strong base...
+ 2 HCl → SrCl2 + 2 H2O
Crystallization from cold aqueous solution gives the hexahydrate
Water of crystallization
In crystallography, water of crystallization or water of hydration or crystallization water is water that occurs in crystals. Water of crystallization is necessary for the maintenance of crystalline properties, but capable of being removed by sufficient heat...
, SrCl2·6H2O. Dehydration of this salt occurs in stages, commencing above 61 °C. Full dehydration occurs at 320 °C.
Structure
The solid adopts a deformed rutileTitanium dioxide
Titanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula . When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891. Generally it comes in two different forms, rutile and anatase. It has a wide range of...
structure. In the vapour phase the SrCl2 molecule is non-linear with a Cl-Sr-Cl angle of approximately 130°. This is an exception to VSEPR theory which would predict a linear structure. Ab initio calculations have been cited to propose that contributions from d orbitals in the shell below the valence shell are responsible. Another proposal is that polarisation of the electron core of the strontium atom causes a distortion of the core electron density that interacts with the Sr-Cl bonds.
Uses
Strontium chloride is the precursorPrecursor (chemistry)
In chemistry, a precursor is a compound that participates in the chemical reaction that produces another compound. In biochemistry, the term "precursor" is used more specifically to refer to a chemical compound preceding another in a metabolic pathway....
to other compounds of strontium, such as yellow strontium chromate, which is used as a corrosion inhibitor for aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
. The precipitation proceeds analogously to the related, isostructural sulfate:
- SrCl2 + Na2CrO4ChromateChromate salts contain the chromate anion, CrO42−. Dichromate salts contain the dichromate anion, Cr2O72−. They are oxyanions of chromium in the oxidation state +6. They are moderately strong oxidizing agents.- Chemical properties :...
→ SrCrO4 + 2 NaClSodium chlorideSodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...
Strontium chloride is often used as a red colouring agent in pyrotechnics
Pyrotechnics
Pyrotechnics is the science of using materials capable of undergoing self-contained and self-sustained exothermic chemical reactions for the production of heat, light, gas, smoke and/or sound...
. It imparts a much more intense red colour to the flames than most other alternatives. It is employed in small quantities in glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
-making and metallurgy
Metallurgy
Metallurgy is a domain of materials science that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their mixtures, which are called alloys. It is also the technology of metals: the way in which science is applied to their practical use...
. The radioactive isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
strontium-89, used for the treatment of bone cancer, is usually administered in the form of strontium chloride. Sea water aquaria
Aquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
require small amounts of strontium chloride, which is consumed in the production of the exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
s of certain plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
.
Dental care
SrCl2 is useful in reducing tooth sensitivity by forming a barrier over microscopic tubules in the dentinDentin
Dentine is a calcified tissue of the body, and along with enamel, cementum, and pulp is one of the four major components of teeth. Usually, it is covered by enamel on the crown and cementum on the root and surrounds the entire pulp...
containing nerve endings that have become exposed by gum recession. Known in the US as Elecol and Sensodyne
Sensodyne
Sensodyne is a toothpaste, toothbrush and mouthwash marketed for individuals with sensitive teeth and/or dentine hypersensitivity. It is a registered trademark of GlaxoSmithKline which acquired it in 2001 in the purchase of Block Drug which developed it....
, these products are called "strontium chloride toothpastes", although most now use potassium nitrate
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...
instead which works as a nerve calming agent rather than a barrier.http://www.sensodyne.co.uk/how_it_works.htm