Rubidium is the
chemical element
A chemical element is a species of atoms that have a given number of protons in their atomic nucleus, nuclei, including the pure Chemical substance, substance consisting only of that species. Unlike chemical compounds, chemical elements canno ...
with the
symbol
A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different conc ...
Rb and
atomic number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of ever ...
37. It is a very soft, whitish-grey solid in the
alkali metal
The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...
group, similar to
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
and
caesium
Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that a ...
. Rubidium is the first
alkali metal
The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...
in the group to have a density higher than
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
. On Earth, natural rubidium comprises two
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass num ...
s: 72% is a stable isotope
85Rb, and 28% is slightly
radioactive
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...
87Rb, with a
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ...
of 48.8 billion years—more than three times as long as the estimated
age of the universe.
German chemists
Robert Bunsen and
Gustav Kirchhoff discovered rubidium in 1861 by the newly developed technique,
flame spectroscopy. The name comes from the
Latin
Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
word , meaning deep red, the color of its emission spectrum. Rubidium's compounds have various chemical and electronic applications. Rubidium metal is easily vaporized and has a convenient spectral absorption range, making it a frequent target for
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The ...
manipulation of
atom
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons.
Every solid, liquid, gas, a ...
s. Rubidium is not a known nutrient for any
living organisms
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fun ...
. However, rubidium
ions have similar properties and the same charge as potassium ions, and are actively taken up and treated by
animal cells in similar ways.
Characteristics
Rubidium is a very soft,
ductile, silvery-white metal.
It is the second most
electropositive of the stable alkali metals and melts at a temperature of . Like other alkali metals, rubidium metal reacts violently with water. As with potassium (which is slightly less reactive) and caesium (which is slightly more reactive), this reaction is usually vigorous enough to ignite the
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...
gas it produces. Rubidium has also been reported to ignite spontaneously in air.
It forms
amalgams with
mercury and
alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductili ...
s with
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
,
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...
,
caesium
Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that a ...
,
sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
, and
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
, but not
lithium
Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense soli ...
(even though rubidium and lithium are in the same group).
Rubidium has a very low
ionization energy of only 406 kJ/mol. Rubidium and potassium show a very similar purple color in the
flame test, and distinguishing the two elements requires more sophisticated analysis, such as spectroscopy.
Compounds
Rubidium chloride (RbCl) is probably the most used rubidium compound: among several other chlorides, it is used to induce living cells to take up
DNA; it is also used as a biomarker, because in nature, it is found only in small quantities in living organisms and when present, replaces potassium. Other common rubidium compounds are the corrosive
rubidium hydroxide (RbOH), the starting material for most rubidium-based chemical processes;
rubidium carbonate (Rb
2CO
3), used in some optical glasses, and rubidium copper sulfate, Rb
2SO
4·CuSO
4·6H
2O.
Rubidium silver iodide (RbAg
4I
5) has the highest
room temperature conductivity of any known
ionic crystal, a property exploited in thin film
batteries
Battery most often refers to:
* Electric battery, a device that provides electrical power
* Battery (crime), a crime involving unlawful physical contact
Battery may also refer to:
Energy source
*Automotive battery, a device to provide power t ...
and other applications.
Rubidium forms a number of
oxides when exposed to air, including rubidium monoxide (Rb
2O), Rb
6O, and Rb
9O
2; rubidium in excess oxygen gives the
superoxide RbO2. Rubidium forms salts with halogens, producing
rubidium fluoride,
rubidium chloride,
rubidium bromide, and
rubidium iodide.
Isotopes
Although rubidium is
monoisotopic, rubidium in the Earth's crust is composed of two isotopes: the stable
85Rb (72.2%) and the
radioactive
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...
87Rb (27.8%).
Natural rubidium is radioactive, with specific activity of about 670
Bq/g, enough to significantly expose a
photographic film
Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the crystals determine ...
in 110 days. Thirty additional rubidium isotopes have been synthesized with half-lives of less than 3 months; most are highly radioactive and have few uses.
Rubidium-87 has a
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ...
of years, which is more than three times the
age of the universe of years,
making it a
primordial nuclide
In geochemistry, geophysics and nuclear physics, primordial nuclides, also known as primordial isotopes, are nuclides found on Earth that have existed in their current form since before Earth was formed. Primordial nuclides were present in the ...
. It readily substitutes for
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
in
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
s, and is therefore fairly widespread. Rb has been used extensively in
dating rocks;
87Rb
beta decay
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...
s to stable
87Sr. During
fractional crystallization, Sr tends to concentrate in
plagioclase
Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more p ...
, leaving Rb in the liquid phase. Hence, the Rb/Sr ratio in residual
magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natura ...
may increase over time, and the progressing
differentiation results in rocks with elevated Rb/Sr ratios. The highest ratios (10 or more) occur in
pegmatites. If the initial amount of Sr is known or can be extrapolated, then the age can be determined by measurement of the Rb and Sr concentrations and of the
87Sr/
86Sr ratio. The dates indicate the true age of the minerals only if the rocks have not been subsequently altered (see
rubidium–strontium dating).
Rubidium-82, one of the element's non-natural isotopes, is produced by
electron-capture decay of
strontium-82 with a half-life of 25.36 days. With a half-life of 76 seconds, rubidium-82 decays by positron emission to stable
krypton-82.
Occurrence
Rubidium is the twenty-third
most abundant element in the Earth's crust, roughly as abundant as
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
and rather more common than
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...
.
It occurs naturally in the minerals
leucite,
pollucite,
carnallite
Carnallite (also carnalite) is an evaporite mineral, a hydrated potassium magnesium chloride with formula KMgCl3·6(H2O). It is variably colored yellow to white, reddish, and sometimes colorless or blue. It is usually massive to fibrous with rar ...
, and
zinnwaldite
Zinnwaldite, K Li Fe Al(Al Si3) O10(O H, F)2, potassium lithium iron aluminium silicate hydroxide fluoride is a silicate mineral in the mica group. The IMA status is as a series between siderophyllite (KFe2Al(Al2Si2)O10(F,OH)2) and polylithioni ...
, which contain as much as 1% rubidium
oxide.
Lepidolite
Lepidolite is a lilac-gray or rose-colored member of the mica group of minerals with chemical formula . It is the most abundant lithium-bearing mineral and is a secondary source of this metal. It is the major source of the alkali metal rubidium.
...
contains between 0.3% and 3.5% rubidium, and is the commercial source of the element. Some
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
minerals and
potassium chlorides also contain the element in commercially significant quantities.
Seawater
Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appro ...
contains an average of 125 µg/L of rubidium compared to the much higher value for potassium of 408 mg/L and the much lower value of 0.3 µg/L for caesium. Rubidium is the 18th most abundant element in seawater.
Because of its large
ionic radius, rubidium is one of the "
incompatible elements." During
magma crystallization, rubidium is concentrated together with its heavier analogue caesium in the liquid phase and crystallizes last. Therefore, the largest deposits of rubidium and caesium are zone
pegmatite ore bodies formed by this enrichment process. Because rubidium substitutes for
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
in the crystallization of magma, the enrichment is far less effective than that of caesium. Zone pegmatite ore bodies containing mineable quantities of caesium as
pollucite or the lithium minerals
lepidolite
Lepidolite is a lilac-gray or rose-colored member of the mica group of minerals with chemical formula . It is the most abundant lithium-bearing mineral and is a secondary source of this metal. It is the major source of the alkali metal rubidium.
...
are also a source for rubidium as a by-product.
Two notable sources of rubidium are the rich deposits of
pollucite at
Bernic Lake,
Manitoba
Manitoba ( ) is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population o ...
, Canada, and the
rubicline found as impurities in pollucite on the Italian island of
Elba, with a rubidium content of 17.5%. Both of those deposits are also sources of caesium.
Production
Although rubidium is more abundant in Earth's crust than caesium, the limited applications and the lack of a mineral rich in rubidium limits the production of rubidium compounds to 2 to 4
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s per year.
Several methods are available for separating potassium, rubidium, and caesium. The
fractional crystallization of a rubidium and caesium alum yields after 30 subsequent steps pure rubidium alum. Two other methods are reported, the chlorostannate process and the ferrocyanide process.
For several years in the 1950s and 1960s, a by-product of potassium production called Alkarb was a main source for rubidium. Alkarb contained 21% rubidium, with the rest being potassium and a small amount of caesium. Today the largest producers of caesium produce rubidium as a by-product from pollucite.
History
Rubidium was discovered in 1861 by
Robert Bunsen and
Gustav Kirchhoff, in Heidelberg, Germany, in the mineral
lepidolite
Lepidolite is a lilac-gray or rose-colored member of the mica group of minerals with chemical formula . It is the most abundant lithium-bearing mineral and is a secondary source of this metal. It is the major source of the alkali metal rubidium.
...
through
flame spectroscopy. Because of the bright red lines in its
emission spectrum
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an electron making a transition from a high energy state to a lower energy state. The photon energy of ...
, they chose a name derived from the
Latin
Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
word , meaning "deep red".
Rubidium is a minor component in
lepidolite
Lepidolite is a lilac-gray or rose-colored member of the mica group of minerals with chemical formula . It is the most abundant lithium-bearing mineral and is a secondary source of this metal. It is the major source of the alkali metal rubidium.
...
. Kirchhoff and Bunsen processed 150 kg of a lepidolite containing only 0.24% rubidium monoxide (Rb
2O). Both potassium and rubidium form insoluble salts with
chloroplatinic acid, but those salts show a slight difference in solubility in hot water. Therefore, the less soluble rubidium
hexachloroplatinate (Rb
2PtCl
6) could be obtained by
fractional crystallization. After reduction of the hexachloroplatinate with
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...
, the process yielded 0.51 grams of
rubidium chloride (RbCl) for further studies. Bunsen and Kirchhoff began their first large-scale isolation of caesium and rubidium compounds with of mineral water, which yielded 7.3 grams of
caesium chloride
Caesium chloride or cesium chloride is the inorganic compound with the formula Cs Cl. This colorless salt is an important source of caesium ions in a variety of niche applications. Its crystal structure forms a major structural type where each ca ...
and 9.2 grams of
rubidium chloride.
Rubidium was the second element, shortly after caesium, to be discovered by spectroscopy, just one year after the invention of the
spectroscope by Bunsen and Kirchhoff.
The two scientists used the rubidium chloride to estimate that the
atomic weight of the new element was 85.36 (the currently accepted value is 85.47).
They tried to generate elemental rubidium by electrolysis of molten rubidium chloride, but instead of a metal, they obtained a blue homogeneous substance, which "neither under the naked eye nor under the microscope showed the slightest trace of metallic substance". They presumed that it was a
subchloride (); however, the product was probably a
colloidal mixture of the metal and rubidium chloride. In a second attempt to produce metallic rubidium, Bunsen was able to reduce rubidium by heating charred rubidium
tartrate. Although the distilled rubidium was
pyrophoric
A substance is pyrophoric (from grc-gre, πυροφόρος, , 'fire-bearing') if it ignites spontaneously in air at or below (for gases) or within 5 minutes after coming into contact with air (for liquids and solids). Examples are organolith ...
, they were able to determine the density and the melting point. The quality of this research in the 1860s can be appraised by the fact that their determined density differs by less than 0.1 g/cm
3 and the melting point by less than 1 °C from the presently accepted values.
The slight radioactivity of rubidium was discovered in 1908, but that was before the theory of isotopes was established in 1910, and the low level of activity (half-life greater than 10
10 years) made interpretation complicated. The now proven decay of
87Rb to stable
87Sr through
beta decay
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...
was still under discussion in the late 1940s.
Rubidium had minimal industrial value before the 1920s. Since then, the most important use of rubidium is research and development, primarily in chemical and electronic applications. In 1995, rubidium-87 was used to produce a
Bose–Einstein condensate, for which the discoverers,
Eric Allin Cornell,
Carl Edwin Wieman and
Wolfgang Ketterle, won the 2001
Nobel Prize in Physics
)
, image = Nobel Prize.png
, alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...
.
Applications
Rubidium compounds are sometimes used in
fireworks
Fireworks are a class of low explosive pyrotechnic devices used for aesthetic and entertainment purposes. They are most commonly used in fireworks displays (also called a fireworks show or pyrotechnics), combining a large number of devices ...
to give them a purple color. Rubidium has also been considered for use in a
thermoelectric generator using the
magnetohydrodynamic principle, whereby hot rubidium ions are passed through a
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
. These conduct electricity and act like an
armature of a generator, thereby generating an
electric current
An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The movi ...
. Rubidium, particularly vaporized
87Rb, is one of the most commonly used atomic species employed for
laser cooling
Laser cooling includes a number of techniques in which atoms, molecules, and small mechanical systems are cooled, often approaching temperatures near absolute zero. Laser cooling techniques rely on the fact that when an object (usually an atom) ...
and
Bose–Einstein condensation Bose–Einstein may refer to:
* Bose–Einstein condensate
** Bose–Einstein condensation (network theory)
* Bose–Einstein correlations
* Bose–Einstein statistics
In quantum statistics, Bose–Einstein statistics (B–E statistics) describe ...
. Its desirable features for this application include the ready availability of inexpensive
diode laser light at the relevant
wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...
and the moderate temperatures required to obtain substantial vapor pressures. For cold-atom applications requiring tunable interactions,
85Rb is preferred for its rich
Feshbach spectrum.
Rubidium has been used for polarizing
3He, producing volumes of magnetized
3He gas, with the nuclear spins aligned rather than random. Rubidium vapor is optically pumped by a laser, and the polarized Rb polarizes
3He through the
hyperfine
In atomic physics, hyperfine structure is defined by small shifts in otherwise degenerate energy levels and the resulting splittings in those energy levels of atoms, molecules, and ions, due to electromagnetic multipole interaction between the ...
interaction. Such
spin-polarized 3He cells are useful for neutron polarization measurements and for producing polarized neutron beams for other purposes.
The resonant element in
atomic clock
An atomic clock is a clock that measures time by monitoring the resonant frequency of atoms. It is based on atoms having different energy levels. Electron states in an atom are associated with different energy levels, and in transitions betwe ...
s utilizes the
hyperfine structure
In atomic physics, hyperfine structure is defined by small shifts in otherwise degenerate energy levels and the resulting splittings in those energy levels of atoms, molecules, and ions, due to electromagnetic multipole interaction between the n ...
of rubidium's energy levels, and rubidium is useful for high-precision timing. It is used as the main component of secondary frequency references (rubidium oscillators) in cell site transmitters and other electronic transmitting, networking, and test equipment. These
rubidium standards are often used with
GPS to produce a "primary frequency standard" that has greater accuracy and is less expensive than caesium standards.
Such rubidium standards are often mass-produced for the
telecommunication
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that ...
industry.
Other potential or current uses of rubidium include a working fluid in vapor turbines, as a
getter in
vacuum tube
A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.
The type known as ...
s, and as a
photocell component. Rubidium is also used as an ingredient in special types of glass, in the production of
superoxide by burning in
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
, in the study of
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
ion channel
Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ...
s in biology, and as the vapor in atomic
magnetometer
A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...
s.
In particular,
87Rb is used with other alkali metals in the development of spin-exchange relaxation-free
(SERF) magnetometers.
Rubidium-82 is used for
positron emission tomography. Rubidium is very similar to potassium, and tissue with high potassium content will also accumulate the radioactive rubidium. One of the main uses is
myocardial perfusion imaging. As a result of changes in the
blood–brain barrier in brain tumors, rubidium collects more in brain tumors than normal brain tissue, allowing the use of radioisotope rubidium-82 in
nuclear medicine
Nuclear medicine or nucleology is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear imaging, in a sense, is " radiology done inside out" because it records radiation emi ...
to locate and image brain tumors. Rubidium-82 has a very short half-life of 76 seconds, and the production from decay of
strontium-82 must be done close to the patient.
Rubidium was tested for the influence on manic depression and depression.
Dialysis patients suffering from depression show a depletion in rubidium, and therefore a supplementation may help during depression. In some tests the rubidium was administered as rubidium chloride with up to 720 mg per day for 60 days.
Precautions and biological effects
Rubidium reacts violently with water and can cause fires. To ensure safety and purity, this metal is usually kept under dry
mineral oil
Mineral oil is any of various colorless, odorless, light mixtures of higher alkanes from a mineral source, particularly a distillate of petroleum, as distinct from usually edible vegetable oils.
The name 'mineral oil' by itself is imprecise ...
or sealed in glass ampoules in an inert atmosphere. Rubidium forms
peroxide
In chemistry, peroxides are a group of compounds with the structure , where R = any element. The group in a peroxide is called the peroxide group or peroxo group. The nomenclature is somewhat variable.
The most common peroxide is hydrogen p ...
s on exposure even to a small amount of air diffused into the oil, and storage is subject to similar precautions as the storage of metallic
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
.
Rubidium, like sodium and potassium, almost always has +1
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
when dissolved in water, even in biological contexts. The human body tends to treat Rb
+ ions as if they were potassium ions, and therefore concentrates rubidium in the body's
intracellular fluid (i.e., inside cells). The ions are not particularly toxic; a 70 kg person contains on average 0.36 g of rubidium, and an increase in this value by 50 to 100 times did not show negative effects in test persons. The
biological half-life of rubidium in humans measures 31–46 days.
Although a partial substitution of potassium by rubidium is possible, when more than 50% of the potassium in the muscle tissue of rats was replaced with rubidium, the rats died.
References
Further reading
* Meites, Louis (1963). ''Handbook of Analytical Chemistry'' (New York: McGraw-Hill Book Company, 1963)
*
External links
*
Rubidiumat ''
The Periodic Table of Videos'' (University of Nottingham)
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Chemical elements
Alkali metals
Reducing agents
Chemical elements with body-centered cubic structure