Strontium
Encyclopedia
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 strontianite
. While natural strontium is stable, the synthetic 90Sr
isotope
is present in radioactive fallout
and has a half-life
of 28.90 years. Both strontium and strontianite are named after Strontian
, a village in Scotland near which the mineral was first discovered.
Strontium is a grey, silvery metal that is softer than calcium
and even more reactive in water
, with which it reacts on contact to produce strontium hydroxide
and hydrogen
gas. It burns in air to produce both strontium oxide
and strontium nitride
, but since it does not react with nitrogen
below 380 °C, at room temperature it will only form the oxide spontaneously.
Because of its extreme reactivity with oxygen and water, this element occurs naturally only in compounds with other elements, such as in the minerals strontianite
and celestite. It is kept under a liquid hydrocarbon such as mineral oil
or kerosene
to prevent oxidation; freshly exposed strontium metal rapidly turns a yellow
ish color with the formation of the oxide. Finely powdered strontium metal is pyrophoric meaning it will ignite spontaneously in air at room temperature. Volatile strontium salts impart a bright red
color to flames
, and these salts are used in pyrotechnics and in the production of flares
. Natural strontium is a mixture of four stable isotope
s.
(Gaelic Sron an t-Sithein), having been discovered in the ores taken from the lead mines. In 1790, Adair Crawford
, a physician engaged in the preparation of barium, recognised that the Strontian ores exhibited different properties to those normally seen with other "heavy spars" sources. This allowed him to conclude "... it is probable indeed, that the scotch mineral is a new species of earth which has not hitherto been sufficiently examined". The new mineral was named strontites in 1793 by Thomas Charles Hope
, a professor of chemistry at the University of Glasgow. He confirmed the earlier work of Crawford and recounted: " ... Considering it a peculiar earth I thought it necessary to give it an name. I have called it Strontites, from the place it was found; a mode of derivation in my opinion, fully as proper as any quality it may possess, which is the present fashion". The element was eventually isolated by Sir Humphry Davy
in 1808 by the electrolysis
of a mixture containing strontium chloride
and mercuric oxide, and announced by him in a lecture to the Royal Society on 30 June 1808. In keeping with the naming of the other alkaline earths, he changed the name to strontium.
The first large scale application of strontium was in the production of sugar from sugar beet
. Although a crystallisation process using strontium hydroxide was patented by Augustin-Pierre Dubrunfaut
in 1849 the large scale introduction came with the improvement of the process in the early 1870s. The German sugar industry used the process well into the 19th century. Prior to World War I
the beet sugar industry used 100,000 to 150,000 tons of strontium hydroxide for this process per year. The strontium hydroxide was recycled in the process, but the demand to substitute losses during production was high enough to create a significant demand initiating mining of strontianite
in the Münsterland. The mining of strontianite in Germany ended when mining of the celestite deposits in Gloucestershire
started. These mines supplied most of the world strontium supply from 1884 to 1941
According to the British Geological Survey
, China was the top producer of strontium in 2007, with over two-thirds world share, followed by Spain, Mexico, Turkey, Argentina and Iran.
Strontium commonly occurs in nature, the 15th most abundant element
on earth, averaging 0.034% of all igneous rock and is found chiefly as the form of the sulfate
mineral
celestite
(SrSO4) and the carbonate
strontianite
(SrCO3). Of the two, celestite occurs much more frequently in sedimentary deposits of sufficient size to make development of mining facilities attractive. Strontianite would be the more useful of the two common minerals because strontium is used most often in the carbonate form, but few deposits have been discovered that are suitable for development. The metal
can be prepared by electrolysis
of melted strontium chloride
mixed with potassium chloride
:
Alternatively it is made by reducing strontium oxide
with aluminium
in a vacuum
at a temperature at which strontium distills
off. Three allotropes of the metal exist, with transition point
s at 235 and 540 °C.
s:
84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). Only 87Sr is radiogenic; it is produced by decay from the radioactive alkali metal 87Rb
, which has a half-life
of 4.88 × 1010 years. Thus, there are two sources of 87Sr in any material: that formed in stars along with 84Sr, 86Sr and 88Sr, as well as that formed by radioactive decay of 87Rb. The ratio 87Sr/86Sr is the parameter typically reported in geologic
investigations; ratios in minerals and rock
s have values ranging from about 0.7 to greater than 4.0. Because strontium has an atomic radius
similar to that of calcium
, it readily substitutes for Ca in mineral
s.
Sixteen unstable isotopes are known to exist. Of greatest importance are 90Sr with a half-life
of 28.78 years and 89Sr with a half-life
of 50.5 days. 90Sr
is a by-product of nuclear fission
found in nuclear fallout
and presents a health problem since it substitutes for calcium in bone
, preventing expulsion from the body. This isotope is one of the best long-lived high-energy beta emitters known, and is used in SNAP (Systems for Nuclear Auxiliary Power) devices. These devices hold promise for use in spacecraft
, remote weather stations, navigational buoys, etc., where a lightweight, long-lived, nuclear-electric power source is required. The 1986 Chernobyl nuclear accident contaminated a vast area with 90Sr. 90Sr confined inside a concave silver plaque is also used for the medical treatment of a resected pterygium.
89Sr is a short-lived artificial radioisotope that is used in the treatment of bone cancer. In circumstances where cancer patients have widespread and painful bony metastases (secondaries)
, the administration of 89Sr results in the delivery of radioactive emissions (beta particle
s in this case) directly to the area of bony problem (where calcium turnover is greatest). The 89Sr is manufactured as the chloride salt (which is soluble), and when dissolved in normal saline can be injected intravenously. Typically, cancer patients will be treated with a dose of 150 MBq
. Patients must take precautions following this because their urine becomes contaminated with radioactivity, so they must sit to urinate and double-flush the toilet. The beta particle
s travel about 3.5 mm in bone (energy 0.583 MeV) and 6.5 mm in tissue, so there is no requirement to isolate patients having been treated, except to say they should not have any one (especially young children) sitting in their laps for 10–40 days. The variation in time results from the variable clearing time for 89Sr, which depends on renal function and the number of bony metastases. With a lot of bony metastases, the entire 89Sr dose can be taken up into bone and so the radioactivity is retained to decay over a 50.5-day half-life. It takes about 10 half-lives or about 500 days for 99.9% of the radioactive strontium to decay. However, where there are few bony metastases, the large proportion of 89Sr not taken up by the bone will be filtered by the kidney, so that the effective half-life (a combination of the physical and biological half-life) will be much shorter.
s of an eutectic composition for the modification of aluminium-silicon casting alloys.
Strontium is 2% by weight of AJ62 alloy, a durable, creep-resistant magnesium alloy
used in car and motorcycle engines by BMW
.
Strontium is used in scientific studies of neurotransmitter
release in neurons. Like calcium, strontium facilitates synaptic vesicle
fusion with the synaptic membrane. But, unlike calcium, strontium causes asynchronous vesicle fusion. Therefore, replacing calcium in the culture medium with strontium allows scientists to measure the effects of a single-vesicle fusion event, e.g., the size of the postsynaptic response elicited by the neurotransmitter content of a single vesicle.
In general, strontium salts often strontium carbonate
are used in the manufacture of fireworks, as they impart a deep red colour to the firework.
The primary use for strontium compounds is in glass
for colour television cathode ray tube
s to prevent X-ray
emission. All parts of the CRT tube have to absorb X-rays. In the neck and the funnel of the tube, lead glass is used for this purpose, but this type of glass shows a browning effect due to the interaction of the X-rays with the glass. Therefore, the front panel has to use a different glass mixture, in which strontium and barium are the X-ray-absorbing materials. The average values for the glass mixture determined for a recycling study in 2005 is 8.5% strontium oxide
and 10% barium oxide
.
Other applications are as follows:
is the active ingredient in Metastron (the generic version of Metastron, Generic Strontium Chloride Sr-89 Injection, its manufactured by Bio-Nucleonics Inc
.), a radiopharmaceutical used for bone pain secondary to metastatic bone cancer. The strontium acts like calcium
and is preferentially incorporated into bone at sites of increased osteogenesis. This localization focuses the radiation exposure on the cancerous lesion.
90Sr
has been used as a power source for radioisotope thermoelectric generator
s (RTGs). 90Sr produces about 0.93 watts of heat per gram (it is lower for the form of 90Sr used in RTGs, which is strontium fluoride
). However, 90Sr has a lifetime approximately 3 times shorter and has a lower density than 238Pu
, another RTG fuel. The main advantage of 90Sr is that it is cheaper than 238Pu and is found in nuclear waste. Soviet Union deployed nearly 1000 of these RTGs on the northern coast as power source for lighthouses and meteorology stations.
90Sr is also used in cancer
therapy. Its beta emission and long half-life is ideal for superficial radiotherapy.
Because strontium is so similar to calcium, it is incorporated in the bone. All four stable isotopes are incorporated, in roughly similar proportions, as they are found in nature (please see below). However, the actual distribution of the isotopes tends to vary greatly from one geographical location to another. Thus, analyzing the bone of an individual can help determine the region it came from. This approach helps to identify the ancient migration patterns as well as the origin of commingled human remains in battlefield burial sites. Strontium, thus, helps forensic scientists too.
87Sr/86Sr ratios are commonly used to determine the likely provenance areas of sediment in natural systems, especially in marine and fluvial environments. Dasch (1969) showed that surface sediments of Atlantic displayed 87Sr/86Sr ratios that could be regarded as bulk averages of the 87Sr/86Sr ratios of geological terranes from adjacent landmasses. A good example of a fluvial-marine system to which Sr isotope provenance studies have been successfully employed is the River Nile-Mediterranean system, Due to the differing ages of the rocks that constitute the majority of the Blue and White Nile, catchment areas of the changing provenance of sediment reaching the River Nile delta and East Mediterranean Sea can be discerned through Sr isotopic studies. Such changes are climatically controlled in the Late Quaternary
.
More recently, 87Sr/86Sr ratios have also been used to determine the source of ancient archaeological materials such as timbers and corn in Chaco Canyon, New Mexico. 87Sr/86Sr ratios in teeth may also be used to track animal migrations or in criminal forensics.
body absorbs strontium as if it were calcium
. Due to the chemical similarity of the elements, the stable forms of strontium might not pose a significant health threat — in fact, the levels found naturally may actually be beneficial (see below) - but the radioactive 90Sr can lead to various bone
disorders and disease
s, including bone cancer. The strontium unit
is used in measuring radioactivity from absorbed 90Sr.
A recent in-vitro study conducted the NY College of Dental Sciences using strontium on osteoblast
s showed marked improvement on bone-building osteoblasts.
The drug strontium ranelate
, made by combining strontium with ranelic acid
, was found to aid bone
growth, increase bone density, and lessen vertebral, peripheral, and hip fractures. Women receiving the drug showed a 12.7% increase in bone density. Women receiving a placebo had a 1.6% decrease. Half the increase in bone density (measured by X-ray densitometry) is attributed to the higher atomic weight of Sr compared with calcium, whereas the other half a true increase in bone mass. Strontium ranelate is registered as a prescription drug in Europe and many countries worldwide. It must be prescribed by a doctor, must be delivered by a pharmacist, and requires strict medical supervision.
There is a long history of medical research regarding strontium's benefits, beginning in the 1950s. Studies indicate a lack of undesirable side-effects. Several other salts of strontium such as strontium citrate and strontium carbonate are available in the United States under the Dietary Supplements Health and Education Act of 1994, providing close to the recommended strontium content, about 680 milligrams per day, of strontium ranelate. Their long-term safety and efficacy have not been evaluated on humans in large-scale medical trials.
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
with the symbol Sr and the atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
38. An alkaline earth metal
Alkaline earth metal
The alkaline earth metals are a group in the periodic table. In the modern IUPAC nomenclature, the alkaline earth metals are called the group 2 elements. Previously, they were called the Group IIA elements . The alkaline earth metals contain beryllium , magnesium , calcium , strontium , barium and...
, 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 strontianite
Strontianite
Strontianite is an important raw material for the extraction of strontium. It is a rare carbonate mineral and one of only a few strontium minerals...
. While natural strontium is stable, the synthetic 90Sr
Strontium-90
Strontium-90 is a radioactive isotope of strontium, with a half-life of 28.8 years.-Radioactivity:Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard...
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...
is present in radioactive fallout
Nuclear fallout
Fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...
and has a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 28.90 years. Both strontium and strontianite are named after Strontian
Strontian
Strontian is the main village in Sunart, an area in western Lochaber, Highland, Scotland, on the A861 road. It lies on the north shore of Loch Sunart, close to the head of the loch...
, a village in Scotland near which the mineral was first discovered.
Characteristics
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 even more reactive in water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
, with which it reacts on contact to produce strontium hydroxide
Strontium 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...
and hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
gas. It burns in air to produce both strontium oxide
Strontium oxide
Strontium oxide or strontia, SrO, is formed when strontium reacts with oxygen. Burning strontium in air results in a mixture of strontium oxide and strontium nitride. It also forms from the decomposition of strontium carbonate SrCO3...
and strontium nitride
Strontium nitride
Strontium nitride, Sr3N2, is produced by burning strontium metal in air or in nitrogen. Like other metal nitrides, it reacts with water to give strontium hydroxide and ammonia:...
, but since it does not react with nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
below 380 °C, at room temperature it will only form the oxide spontaneously.
Because of its extreme reactivity with oxygen and water, this element occurs naturally only in compounds with other elements, such as in the minerals strontianite
Strontianite
Strontianite is an important raw material for the extraction of strontium. It is a rare carbonate mineral and one of only a few strontium minerals...
and celestite. It is kept under a liquid hydrocarbon such as mineral oil
Mineral oil
A mineral oil is any of various colorless, odorless, light mixtures of alkanes in the C15 to C40 range from a non-vegetable source, particularly a distillate of petroleum....
or kerosene
Kerosene
Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
to prevent oxidation; freshly exposed strontium metal rapidly turns a yellow
Yellow
Yellow is the color evoked by light that stimulates both the L and M cone cells of the retina about equally, with no significant stimulation of the S cone cells. Light with a wavelength of 570–590 nm is yellow, as is light with a suitable mixture of red and green...
ish color with the formation of the oxide. Finely powdered strontium metal is pyrophoric meaning it will ignite spontaneously in air at room temperature. Volatile strontium salts impart a bright red
Red
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...
color to flames
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....
, and these salts are used in pyrotechnics and in the production of flares
Flare (pyrotechnic)
A flare, also sometimes called a fusee, is a type of pyrotechnic that produces a brilliant light or intense heat without an explosion. Flares are used for signalling, illumination, or defensive countermeasures in civilian and military applications...
. Natural strontium is a mixture of four stable 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...
s.
History
Strontium is named after the Scottish village of StrontianStrontian
Strontian is the main village in Sunart, an area in western Lochaber, Highland, Scotland, on the A861 road. It lies on the north shore of Loch Sunart, close to the head of the loch...
(Gaelic Sron an t-Sithein), having been discovered in the ores taken from the lead mines. In 1790, Adair Crawford
Adair Crawford
Adair Crawford FRS , a chemist and physician, was a pioneer in the development of calorimetric methods for measuring the specific heat capacity of substances and the heat of chemical reactions...
, a physician engaged in the preparation of barium, recognised that the Strontian ores exhibited different properties to those normally seen with other "heavy spars" sources. This allowed him to conclude "... it is probable indeed, that the scotch mineral is a new species of earth which has not hitherto been sufficiently examined". The new mineral was named strontites in 1793 by Thomas Charles Hope
Thomas Charles Hope
Thomas Charles Hope was a Scottish physician and chemist. He discovered the element strontium, and gave his name to Hope's Experiment, which shows that water reaches its maximum density at 4°C....
, a professor of chemistry at the University of Glasgow. He confirmed the earlier work of Crawford and recounted: " ... Considering it a peculiar earth I thought it necessary to give it an name. I have called it Strontites, from the place it was found; a mode of derivation in my opinion, fully as proper as any quality it may possess, which is the present fashion". The element was eventually isolated by Sir Humphry Davy
Humphry Davy
Sir Humphry Davy, 1st Baronet FRS MRIA was a British chemist and inventor. He is probably best remembered today for his discoveries of several alkali and alkaline earth metals, as well as contributions to the discoveries of the elemental nature of chlorine and iodine...
in 1808 by the electrolysis
Electrolysis
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...
of a mixture containing strontium chloride
Strontium chloride
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...
and mercuric oxide, and announced by him in a lecture to the Royal Society on 30 June 1808. In keeping with the naming of the other alkaline earths, he changed the name to strontium.
The first large scale application of strontium was in the production of sugar from sugar beet
Sugar beet
Sugar beet, a cultivated plant of Beta vulgaris, is a plant whose tuber contains a high concentration of sucrose. It is grown commercially for sugar production. Sugar beets and other B...
. Although a crystallisation process using strontium hydroxide was patented by Augustin-Pierre Dubrunfaut
Augustin-Pierre Dubrunfaut
Augustin-Pierre Dubrunfaut was a French chemist.Mutarotation was discovered by Dubrunfaut in 1846, when he noticed that the specific rotation of aqueous sugar solution changes with time. The organic fructose molecule was first discovered by Dubrunfaut in 1847.-Works:* Art de fabriquer le sucre de...
in 1849 the large scale introduction came with the improvement of the process in the early 1870s. The German sugar industry used the process well into the 19th century. Prior to World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
the beet sugar industry used 100,000 to 150,000 tons of strontium hydroxide for this process per year. The strontium hydroxide was recycled in the process, but the demand to substitute losses during production was high enough to create a significant demand initiating mining of strontianite
Strontianite
Strontianite is an important raw material for the extraction of strontium. It is a rare carbonate mineral and one of only a few strontium minerals...
in the Münsterland. The mining of strontianite in Germany ended when mining of the celestite deposits in Gloucestershire
Gloucestershire
Gloucestershire is a county in South West England. The county comprises part of the Cotswold Hills, part of the flat fertile valley of the River Severn, and the entire Forest of Dean....
started. These mines supplied most of the world strontium supply from 1884 to 1941
Occurrence
British Geological Survey
The British Geological Survey is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. The BGS headquarters are in Keyworth, Nottinghamshire, but other centres...
, China was the top producer of strontium in 2007, with over two-thirds world share, followed by Spain, Mexico, Turkey, Argentina and Iran.
Strontium commonly occurs in nature, the 15th most abundant element
Abundance of the chemical elements
The abundance of a chemical element measures how relatively common the element is, or how much of the element is present in a given environment by comparison to all other elements...
on earth, averaging 0.034% of all igneous rock and is found chiefly as the form of the sulfate
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
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...
celestite
Celestite
Celestine or celestite is a mineral consisting of strontium sulfate. The mineral is named for its occasional delicate blue color.-Occurrence:Celestine occurs as crystals, and also in compact massive and fibrous forms...
(SrSO4) and the carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
strontianite
Strontianite
Strontianite is an important raw material for the extraction of strontium. It is a rare carbonate mineral and one of only a few strontium minerals...
(SrCO3). Of the two, celestite occurs much more frequently in sedimentary deposits of sufficient size to make development of mining facilities attractive. Strontianite would be the more useful of the two common minerals because strontium is used most often in the carbonate form, but few deposits have been discovered that are suitable for development. The metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
can be prepared by electrolysis
Electrolysis
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...
of melted strontium chloride
Strontium chloride
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...
mixed with potassium chloride
Potassium chloride
The chemical compound potassium chloride is a metal halide salt composed of potassium and chlorine. In its pure state, it is odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are...
:
- Sr2+ + 2 → Sr
- 2 Cl− → Cl2 (g) + 2
Alternatively it is made by reducing strontium oxide
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....
with 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....
in a vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
at a temperature at which strontium distills
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
off. Three allotropes of the metal exist, with transition point
Transition point
In the field of fluid dynamics the point at which the boundary layer changes from laminar to turbulent is called the transition point. Where the boundary layer becomes turbulent, drag due to skin friction is relatively high. As speed increases, the upper surface transition point tends to move...
s at 235 and 540 °C.
Isotopes
Strontium has four stable, naturally occurring isotopeIsotope
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...
s:
84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). Only 87Sr is radiogenic; it is produced by decay from the radioactive alkali metal 87Rb
Rubidium
Rubidium is a chemical element with the symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group. Its atomic mass is 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other elements in group 1, such as very rapid...
, which has a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 4.88 × 1010 years. Thus, there are two sources of 87Sr in any material: that formed in stars along with 84Sr, 86Sr and 88Sr, as well as that formed by radioactive decay of 87Rb. The ratio 87Sr/86Sr is the parameter typically reported in geologic
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
investigations; ratios in minerals and rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...
s have values ranging from about 0.7 to greater than 4.0. Because strontium has an atomic radius
Atomic radius
The atomic radius of a chemical element is a measure of the size of its atoms, usually the mean or typical distance from the nucleus to the boundary of the surrounding cloud of electrons...
similar to that of 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...
, it readily substitutes for Ca in 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...
s.
Sixteen unstable isotopes are known to exist. Of greatest importance are 90Sr with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 28.78 years and 89Sr with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 50.5 days. 90Sr
Strontium-90
Strontium-90 is a radioactive isotope of strontium, with a half-life of 28.8 years.-Radioactivity:Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard...
is a by-product of nuclear fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
found in nuclear fallout
Nuclear fallout
Fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...
and presents a health problem since it substitutes for calcium in bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
, preventing expulsion from the body. This isotope is one of the best long-lived high-energy beta emitters known, and is used in SNAP (Systems for Nuclear Auxiliary Power) devices. These devices hold promise for use in spacecraft
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
, remote weather stations, navigational buoys, etc., where a lightweight, long-lived, nuclear-electric power source is required. The 1986 Chernobyl nuclear accident contaminated a vast area with 90Sr. 90Sr confined inside a concave silver plaque is also used for the medical treatment of a resected pterygium.
89Sr is a short-lived artificial radioisotope that is used in the treatment of bone cancer. In circumstances where cancer patients have widespread and painful bony metastases (secondaries)
Metastasis
Metastasis, or metastatic disease , is the spread of a disease from one organ or part to another non-adjacent organ or part. It was previously thought that only malignant tumor cells and infections have the capacity to metastasize; however, this is being reconsidered due to new research...
, the administration of 89Sr results in the delivery of radioactive emissions (beta particle
Beta particle
Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay...
s in this case) directly to the area of bony problem (where calcium turnover is greatest). The 89Sr is manufactured as the chloride salt (which is soluble), and when dissolved in normal saline can be injected intravenously. Typically, cancer patients will be treated with a dose of 150 MBq
Becquerel
The becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...
. Patients must take precautions following this because their urine becomes contaminated with radioactivity, so they must sit to urinate and double-flush the toilet. The beta particle
Beta particle
Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay...
s travel about 3.5 mm in bone (energy 0.583 MeV) and 6.5 mm in tissue, so there is no requirement to isolate patients having been treated, except to say they should not have any one (especially young children) sitting in their laps for 10–40 days. The variation in time results from the variable clearing time for 89Sr, which depends on renal function and the number of bony metastases. With a lot of bony metastases, the entire 89Sr dose can be taken up into bone and so the radioactivity is retained to decay over a 50.5-day half-life. It takes about 10 half-lives or about 500 days for 99.9% of the radioactive strontium to decay. However, where there are few bony metastases, the large proportion of 89Sr not taken up by the bone will be filtered by the kidney, so that the effective half-life (a combination of the physical and biological half-life) will be much shorter.
Applications
As a pure metal strontium is used in strontium 90%-aluminium 10% alloyAlloy
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 of an eutectic composition for the modification of aluminium-silicon casting alloys.
Strontium is 2% by weight of AJ62 alloy, a durable, creep-resistant magnesium alloy
Magnesium alloy
Magnesium alloys are mixtures of magnesium with other metals , often aluminium, zinc, manganese, silicon, copper, rare earths and zirconium. Magnesium is the lightest structural metal. Magnesium alloys have a hexagonal lattice structure, which affects the fundamental properties of these alloys...
used in car and motorcycle engines by BMW
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...
.
Strontium is used in scientific studies of neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
release in neurons. Like calcium, strontium facilitates synaptic vesicle
Synaptic vesicle
In a neuron, synaptic vesicles store various neurotransmitters that are released at the synapse. The release is regulated by a voltage-dependent calcium channel. Vesicles are essential for propagating nerve impulses between neurons and are constantly recreated by the cell...
fusion with the synaptic membrane. But, unlike calcium, strontium causes asynchronous vesicle fusion. Therefore, replacing calcium in the culture medium with strontium allows scientists to measure the effects of a single-vesicle fusion event, e.g., the size of the postsynaptic response elicited by the neurotransmitter content of a single vesicle.
In general, strontium salts often 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 :...
are used in the manufacture of fireworks, as they impart a deep red colour to the firework.
Compounds
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...
for colour television cathode ray tube
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
s to prevent X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
emission. All parts of the CRT tube have to absorb X-rays. In the neck and the funnel of the tube, lead glass is used for this purpose, but this type of glass shows a browning effect due to the interaction of the X-rays with the glass. Therefore, the front panel has to use a different glass mixture, in which strontium and barium are the X-ray-absorbing materials. The average values for the glass mixture determined for a recycling study in 2005 is 8.5% strontium oxide
Strontium oxide
Strontium oxide or strontia, SrO, is formed when strontium reacts with oxygen. Burning strontium in air results in a mixture of strontium oxide and strontium nitride. It also forms from the decomposition of strontium carbonate SrCO3...
and 10% barium oxide
Barium oxide
Barium oxide, BaO, is a white hygroscopic compound formed by the burning of barium in oxygen, although it is often formed through the decomposition of other barium salts.It reacts with water to form barium hydroxide.-Uses:...
.
Other applications are as follows:
- Ferrite magnets and refining zincZincZinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
. - Strontium titanateStrontium titanateStrontium titanate is an oxide of strontium and titanium with the chemical formula SrTiO3. At room temperature, it is a centrosymmetric paraelectric material with a perovskite structure...
has an extremely high refractive indexRefractive indexIn optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
and an optical dispersion greater than that of diamondDiamondIn mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...
, making it useful in a variety of optics applications. This quality has also led to its being cut into gemstoneGemstoneA gemstone or gem is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments...
s, in particular as a diamond simulantDiamond simulantThe high price of gem-grade diamonds, as well as significant ethical concerns of the diamond trade, have created a large demand for materials with similar gemological characteristics, known as diamond simulants or imitations. Simulants are distinct from synthetic diamond, which unlike simulants is...
. However, it is very soft and easily scratches so it is rarely used. - Strontium carbonateStrontium carbonateStrontium 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 :...
, strontium nitrateStrontium nitrateStrontium nitrate is an inorganic compound with the formula Sr2. This colourless solid is used as an colorant in pyrotechnics.- Preparation:Strontium nitrate is typically generated by the reaction of nitric acid on strontium carbonate.....
, and strontium sulfateStrontium sulfateStrontium sulfate is the sulfate salt of strontium. It is a white crystalline powder and occurs in nature as the mineral celestine. It is poorly soluble in water to the extent of 1 part in 8,800. It is more soluble in dilute HCl and nitric acid and appreciably soluble in alkali chloride solutions...
are commonly used in fireworks for red color, and sometimes for other colors too. - Strontium aluminateStrontium aluminateStrontium aluminate is a solid odorless, nonflammable, pale yellow powder, heavier than water. It is chemically and biologically inert. When activated with a suitable dopant , it acts as a photoluminescent phosphor with long persistence of phosphorescence...
is used as a bright phosphorPhosphorA phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
with long persistence of phosphorescencePhosphorescencePhosphorescence is a specific type of photoluminescence related to fluorescence. Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs. The slower time scales of the re-emission are associated with "forbidden" energy state transitions in quantum...
. - Strontium chlorideStrontium chlorideStrontium 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...
is sometimes used in toothpasteToothpasteToothpaste is a paste or gel dentifrice used with a toothbrush as an accessory to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it serves as an abrasive that aids in removing the dental plaque and food from the teeth, assists in suppressing...
s for sensitive teeth. One popular brand includes 10% total strontium chloride hexahydrate by weight. - Strontium oxideStrontium oxideStrontium oxide or strontia, SrO, is formed when strontium reacts with oxygen. Burning strontium in air results in a mixture of strontium oxide and strontium nitride. It also forms from the decomposition of strontium carbonate SrCO3...
is sometimes used to improve the quality of some potteryPotteryPottery is the material from which the potteryware is made, of which major types include earthenware, stoneware and porcelain. The place where such wares are made is also called a pottery . Pottery also refers to the art or craft of the potter or the manufacture of pottery...
glazesCeramic glazeGlaze is a layer or coating of a vitreous substance which has been fired to fuse to a ceramic object to color, decorate, strengthen or waterproof it.-Use:...
. - Strontium ranelateStrontium ranelateStrontium ranelate, a strontium salt of ranelic acid, is a medication for osteoporosis marketed as Protelos or Protos by Servier. It is unusual in the sense that it both increases deposition of new bone osteoblasts and reduces the resorption of bone by osteoclasts...
is used in the treatment of osteoporosis. It is a prescription drug in the EU, but not in the USA. - Strontium barium niobate can be used in outdoors holographic 3D displays as a "screen".
- Strontium phosphide is an inorganic compound with the formula Sr3P2 and is used as a laboratory reagent and in the manufacture of chemically reactive devices.
Radioactive strontium isotopes
89SrStrontium-89
Strontium-89 is an isotope of strontium.It is treated by the body in a similar manner to calcium, and is preferentially deposited metabolically active regions of the bone.It is an artificial radioisotope which is used in treatment of bone cancer...
is the active ingredient in Metastron (the generic version of Metastron, Generic Strontium Chloride Sr-89 Injection, its manufactured by Bio-Nucleonics Inc
Bio-Nucleonics
Bio-Nucleonics Inc. is a privately-held, life sciences company located in the United States. The company develops, manufactures, and markets radiopharmaceuticals, medical devices, and imaging agents to detect and treat cardiovascular, oncological, and neurological diseases. Approved by the U.S Food...
.), a radiopharmaceutical used for bone pain secondary to metastatic bone cancer. The strontium acts like 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 is preferentially incorporated into bone at sites of increased osteogenesis. This localization focuses the radiation exposure on the cancerous lesion.
Strontium-90
Strontium-90 is a radioactive isotope of strontium, with a half-life of 28.8 years.-Radioactivity:Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard...
has been used as a power source for radioisotope thermoelectric generator
Radioisotope thermoelectric generator
A radioisotope thermoelectric generator is an electrical generator that obtains its power from radioactive decay. In such a device, the heat released by the decay of a suitable radioactive material is converted into electricity by the Seebeck effect using an array of thermocouples.RTGs can be...
s (RTGs). 90Sr produces about 0.93 watts of heat per gram (it is lower for the form of 90Sr used in RTGs, which is strontium fluoride
Strontium fluoride
Strontium fluoride, SrF2, also called strontium difluoride and strontium fluoride, is a fluoride of strontium. It is a stable brittle white crystalline solid with melting point of 1477°C and boiling point 2460°C.-Preparation:...
). However, 90Sr has a lifetime approximately 3 times shorter and has a lower density than 238Pu
Plutonium-238
-External links:**...
, another RTG fuel. The main advantage of 90Sr is that it is cheaper than 238Pu and is found in nuclear waste. Soviet Union deployed nearly 1000 of these RTGs on the northern coast as power source for lighthouses and meteorology stations.
90Sr is also used in cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
therapy. Its beta emission and long half-life is ideal for superficial radiotherapy.
Because strontium is so similar to calcium, it is incorporated in the bone. All four stable isotopes are incorporated, in roughly similar proportions, as they are found in nature (please see below). However, the actual distribution of the isotopes tends to vary greatly from one geographical location to another. Thus, analyzing the bone of an individual can help determine the region it came from. This approach helps to identify the ancient migration patterns as well as the origin of commingled human remains in battlefield burial sites. Strontium, thus, helps forensic scientists too.
87Sr/86Sr ratios are commonly used to determine the likely provenance areas of sediment in natural systems, especially in marine and fluvial environments. Dasch (1969) showed that surface sediments of Atlantic displayed 87Sr/86Sr ratios that could be regarded as bulk averages of the 87Sr/86Sr ratios of geological terranes from adjacent landmasses. A good example of a fluvial-marine system to which Sr isotope provenance studies have been successfully employed is the River Nile-Mediterranean system, Due to the differing ages of the rocks that constitute the majority of the Blue and White Nile, catchment areas of the changing provenance of sediment reaching the River Nile delta and East Mediterranean Sea can be discerned through Sr isotopic studies. Such changes are climatically controlled in the Late Quaternary
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...
.
More recently, 87Sr/86Sr ratios have also been used to determine the source of ancient archaeological materials such as timbers and corn in Chaco Canyon, New Mexico. 87Sr/86Sr ratios in teeth may also be used to track animal migrations or in criminal forensics.
Effect on the human body
The humanHuman
Humans are the only living species in the Homo genus...
body absorbs strontium as if it were 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...
. Due to the chemical similarity of the elements, the stable forms of strontium might not pose a significant health threat — in fact, the levels found naturally may actually be beneficial (see below) - but the radioactive 90Sr can lead to various bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
disorders and disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
s, including bone cancer. The strontium unit
Strontium unit
The strontium unit is a unit used to measure the amount of radioactivity from strontium-90, a radionuclide found in nuclear fallout, in a subject's body; as the human body absorbs strontium as if it were calcium, incorporating it into the skeleton, its presence is very common...
is used in measuring radioactivity from absorbed 90Sr.
A recent in-vitro study conducted the NY College of Dental Sciences using strontium on osteoblast
Osteoblast
Osteoblasts are mononucleate cells that are responsible for bone formation; in essence, osteoblasts are specialized fibroblasts that in addition to fibroblastic products, express bone sialoprotein and osteocalcin.Osteoblasts produce a matrix of osteoid, which is composed mainly of Type I collagen...
s showed marked improvement on bone-building osteoblasts.
The drug strontium ranelate
Strontium ranelate
Strontium ranelate, a strontium salt of ranelic acid, is a medication for osteoporosis marketed as Protelos or Protos by Servier. It is unusual in the sense that it both increases deposition of new bone osteoblasts and reduces the resorption of bone by osteoclasts...
, made by combining strontium with ranelic acid
Ranelic acid
Ranelic acid is an organic acid capable of chelating metal cations.It forms the ranelate ion, C12H6N2O8S4-. Strontium ranelate, made by combining strontium with ranelic acid, is a drug used to treat osteoporosis and increase bone mineral density ....
, was found to aid bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
growth, increase bone density, and lessen vertebral, peripheral, and hip fractures. Women receiving the drug showed a 12.7% increase in bone density. Women receiving a placebo had a 1.6% decrease. Half the increase in bone density (measured by X-ray densitometry) is attributed to the higher atomic weight of Sr compared with calcium, whereas the other half a true increase in bone mass. Strontium ranelate is registered as a prescription drug in Europe and many countries worldwide. It must be prescribed by a doctor, must be delivered by a pharmacist, and requires strict medical supervision.
There is a long history of medical research regarding strontium's benefits, beginning in the 1950s. Studies indicate a lack of undesirable side-effects. Several other salts of strontium such as strontium citrate and strontium carbonate are available in the United States under the Dietary Supplements Health and Education Act of 1994, providing close to the recommended strontium content, about 680 milligrams per day, of strontium ranelate. Their long-term safety and efficacy have not been evaluated on humans in large-scale medical trials.
See also
External links
- WebElements.com – Strontium
- Chemistry in its element podcast (MP3) from the Royal Society of ChemistryRoyal Society of ChemistryThe Royal Society of Chemistry is a learned society in the United Kingdom with the goal of "advancing the chemical sciences." It was formed in 1980 from the merger of the Chemical Society, the Royal Institute of Chemistry, the Faraday Society and the Society for Analytical Chemistry with a new...
's Chemistry WorldChemistry WorldChemistry World is a monthly chemistry news magazine published by the Royal Society of Chemistry. The magazine addresses current events in world of chemistry including research, international business news and government policy as it affects the chemical science community, plus the best product...
: Strontium