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85-603: The DS0 rate was introduced to carry a single digitized voice call. For a typical phone call, the audio sound is digitized at an 8 kHz sample rate, or 8000 samples per second, using 8-bit pulse-code modulation for each of the samples. This results in a data rate of 64 kbit/s . Because of its fundamental role in carrying a single phone call, the DS0 rate forms the basis for the digital multiplex transmission hierarchy in telecommunications systems used in North America. To limit

170-489: A colloidal mixture of the metal and caesium chloride. The electrolysis of the aqueous solution of chloride with a mercury cathode produced a caesium amalgam which readily decomposed under the aqueous conditions. The pure metal was eventually isolated by the Swedish chemist Carl Setterberg while working on his doctorate with Kekulé and Bunsen. In 1882, he produced caesium metal by electrolysing caesium cyanide , avoiding

255-407: A spectroscope , which had been invented by Bunsen and Kirchhoff only a year previously. To obtain a pure sample of caesium, 44,000 litres (9,700 imp gal; 12,000 US gal) of mineral water had to be evaporated to yield 240 kilograms (530 lb) of concentrated salt solution. The alkaline earth metals were precipitated either as sulfates or oxalates , leaving the alkali metal in

340-467: A T-carrier system is used as in North America, robbed bit signaling can mean that a DS0 channel carried over that system is not an error-free bit-stream. The out-of-band signaling used in the European E-carrier system avoids this. [REDACTED]  This article incorporates public domain material from Federal Standard 1037C . General Services Administration . Archived from

425-431: A blue or violet colour. Caesium exists in the form of different allotropes , one of them a dimer called dicaesium. Caesium metal is highly reactive and pyrophoric . It ignites spontaneously in air, and reacts explosively with water even at low temperatures, more so than the other alkali metals . It reacts with ice at temperatures as low as −116 °C (−177 °F). Because of this high reactivity, caesium metal

510-442: A dilute chloride (CsCl) solution. This solution can be evaporated to produce caesium chloride or transformed into caesium alum or caesium carbonate. Though not commercially feasible, the ore can be directly reduced with potassium, sodium, or calcium in vacuum to produce caesium metal directly. Most of the mined caesium (as salts) is directly converted into caesium formate (HCOO Cs ) for applications such as oil drilling . To supply

595-424: A heavy element, caesium provides good stopping power with better detection. Caesium compounds may provide a faster response (CsF) and be less hygroscopic (CsI). Caesium vapour is used in many common magnetometers . The element is used as an internal standard in spectrophotometry . Like other alkali metals , caesium has a great affinity for oxygen and is used as a " getter " in vacuum tubes . Other uses of

680-431: A mixture of soluble chlorides is produced, and the insoluble chloride double salts of caesium are precipitated as caesium antimony chloride ( Cs 4 SbCl 7 ), caesium iodine chloride ( Cs 2 ICl ), or caesium hexachlorocerate ( Cs 2 (CeCl 6 ) ). After separation, the pure precipitated double salt is decomposed, and pure CsCl is precipitated by evaporating the water. The sulfuric acid method yields

765-552: A more detailed treatment of this and the above frequency ranges, see Electromagnetic spectrum . Gravitational waves are also described in Hertz. Current observations are conducted in the 30–7000 Hz range by laser interferometers like LIGO , and the nanohertz (1–1000 nHz) range by pulsar timing arrays . Future space-based detectors are planned to fill in the gap, with LISA operating from 0.1–10 mHz (with some sensitivity from 10 μHz to 100 mHz), and DECIGO in

850-419: A very long half-life of about 2.3 million years, the longest of all radioactive isotopes of caesium. Cs and Cs have half-lives of 30 and two years, respectively. Cs decomposes to a short-lived Ba by beta decay , and then to nonradioactive barium, while Cs transforms into Ba directly. The isotopes with mass numbers of 129, 131, 132 and 136, have half-lives between a day and two weeks, while most of

935-577: Is hygroscopic and strongly basic . It rapidly etches the surface of semiconductors such as silicon . CsOH has been previously regarded by chemists as the "strongest base", reflecting the relatively weak attraction between the large Cs ion and OH ; it is indeed the strongest Arrhenius base ; however, a number of compounds such as n -butyllithium , sodium amide , sodium hydride , caesium hydride , etc., which cannot be dissolved in water as reacting violently with it but rather only used in some anhydrous polar aprotic solvents , are far more basic on

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1020-427: Is 1/time (T ). Expressed in base SI units, the unit is the reciprocal second (1/s). In English, "hertz" is also used as the plural form. As an SI unit, Hz can be prefixed ; commonly used multiples are kHz (kilohertz, 10  Hz ), MHz (megahertz, 10  Hz ), GHz (gigahertz, 10  Hz ) and THz (terahertz, 10  Hz ). One hertz (i.e. one per second) simply means "one periodic event occurs per second" (where

1105-456: Is a chemical element ; it has symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of 28.5 °C (83.3 °F; 301.6 K), which makes it one of only five elemental metals that are liquid at or near room temperature . Caesium has physical and chemical properties similar to those of rubidium and potassium . It is pyrophoric and reacts with water even at −116 °C (−177 °F). It

1190-649: Is also larger and less "hard" than those of the lighter alkali metals . Most caesium compounds contain the element as the cation Cs , which binds ionically to a wide variety of anions . One noteworthy exception is the caeside anion ( Cs ), and others are the several suboxides (see section on oxides below). More recently, caesium is predicted to behave as a p-block element and capable of forming higher fluorides with higher oxidation states (i.e., CsF n with n > 1) under high pressure. This prediction needs to be validated by further experiments. Salts of Cs are usually colourless unless

1275-497: Is also liquid at room temperature (melting at −7.2 °C [19.0 °F]), but it is a halogen and not a metal. Mercury is the only stable elemental metal with a known melting point lower than caesium. In addition, the metal has a rather low boiling point , 641 °C (1,186 °F), the lowest of all stable metals other than mercury. Copernicium and flerovium have been predicted to have lower boiling points than mercury and caesium, but they are extremely radioactive and it

1360-519: Is also used as a source of positive ions in secondary ion mass spectrometry (SIMS). Since 1967, the International System of Measurements has based the primary unit of time, the second, on the properties of caesium. The International System of Units (SI) defines the second as the duration of 9,192,631,770 cycles at the microwave frequency of the spectral line corresponding to the transition between two hyperfine energy levels of

1445-494: Is also used to describe the clock speeds at which computers and other electronics are driven. The units are sometimes also used as a representation of the energy of a photon , via the Planck relation E  =  hν , where E is the photon's energy, ν is its frequency, and h is the Planck constant . The hertz is defined as one per second for periodic events. The International Committee for Weights and Measures defined

1530-558: Is classified as a hazardous material . It is stored and shipped in dry, saturated hydrocarbons such as mineral oil . It can be handled only under inert gas , such as argon . However, a caesium-water explosion is often less powerful than a sodium -water explosion with a similar amount of sodium. This is because caesium explodes instantly upon contact with water, leaving little time for hydrogen to accumulate. Caesium can be stored in vacuum-sealed borosilicate glass ampoules . In quantities of more than about 100 grams (3.5 oz), caesium

1615-434: Is crushed, hand-sorted, but not usually concentrated, and then ground. Caesium is then extracted from pollucite primarily by three methods: acid digestion, alkaline decomposition, and direct reduction. In the acid digestion, the silicate pollucite rock is dissolved with strong acids, such as hydrochloric (HCl), sulfuric ( H 2 SO 4 ), hydrobromic (HBr), or hydrofluoric (HF) acids. With hydrochloric acid,

1700-430: Is found in few minerals. Percentage amounts of caesium may be found in beryl ( Be 3 Al 2 (SiO 3 ) 6 ) and avogadrite ( (K,Cs)BF 4 ), up to 15 wt% Cs 2 O in the closely related mineral pezzottaite ( Cs(Be 2 Li)Al 2 Si 6 O 18 ), up to 8.4 wt% Cs 2 O in the rare mineral londonite ( (Cs,K)Al 4 Be 4 (B,Be) 12 O 28 ), and less in

1785-479: Is mined for its petalite, but it also contains a significant amount of pollucite. Another notable source of pollucite is in the Karibib Desert , Namibia . At the present rate of world mine production of 5 to 10 metric tons per year, reserves will last for thousands of years. Mining and refining pollucite ore is a selective process and is conducted on a smaller scale than for most other metals. The ore

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1870-429: Is not certain if they are metals. Caesium forms alloys with the other alkali metals, gold , and mercury ( amalgams ). At temperatures below 650 °C (1,202 °F), it does not alloy with cobalt , iron , molybdenum , nickel , platinum , tantalum , or tungsten . It forms well-defined intermetallic compounds with antimony , gallium , indium , and thorium , which are photosensitive . It mixes with all

1955-481: Is one of the " incompatible elements ". During magma crystallization , caesium is concentrated in the liquid phase and crystallizes last. Therefore, the largest deposits of caesium are zone pegmatite ore bodies formed by this enrichment process. Because caesium does not substitute for potassium as readily as rubidium does, the alkali evaporite minerals sylvite (KCl) and carnallite ( KMgCl 3 ·6H 2 O ) may contain only 0.002% caesium. Consequently, caesium

2040-451: Is reduced in most reactors because the predecessor, Xe , is a potent neutron poison and frequently transmutes to stable Xe before it can decay to Cs. The beta decay from Cs to Ba results in gamma radiation as the Ba relaxes to ground state Ba, with the emitted photons having an energy of 0.6617 MeV. Cs and Sr are the principal medium-lived products of nuclear fission , and

2125-548: Is shipped in hermetically sealed, stainless steel containers. The chemistry of caesium is similar to that of other alkali metals, in particular rubidium , the element above caesium in the periodic table. As expected for an alkali metal, the only common oxidation state is +1. It differs from this value in caesides, which contain the Cs anion and thus have caesium in the −1 oxidation state. Under conditions of extreme pressure (greater than 30  GPa ), theoretical studies indicate that

2210-642: Is the Tanco Mine at Bernic Lake in Manitoba , Canada, estimated to contain 350,000  metric tons of pollucite ore, representing more than two-thirds of the world's reserve base. Although the stoichiometric content of caesium in pollucite is 42.6%, pure pollucite samples from this deposit contain only about 34% caesium, while the average content is 24 wt%. Commercial pollucite contains more than 19% caesium. The Bikita pegmatite deposit in Zimbabwe

2295-552: Is the least electronegative stable element, with a value of 0.79 on the Pauling scale . It has only one stable isotope , caesium-133 . Caesium is mined mostly from pollucite . Caesium-137 , a fission product , is extracted from waste produced by nuclear reactors . It has the largest atomic radius of all elements whose radii have been measured or calculated, at about 260 picometres . The German chemist Robert Bunsen and physicist Gustav Kirchhoff discovered caesium in 1860 by

2380-542: Is the primary standard for standards-compliant time and frequency measurements. Caesium clocks regulate the timing of cell phone networks and the Internet. The second, symbol s , is the SI unit of time. The BIPM restated its definition at its 26th conference in 2018: "[The second] is defined by taking the fixed numerical value of the caesium frequency Δ ν Cs , the unperturbed ground-state hyperfine transition frequency of

2465-728: Is used in photoelectric cells because caesium-based cathodes, such as the intermetallic compound K 2 CsSb , have a low threshold voltage for emission of electrons . The range of photoemissive devices using caesium include optical character recognition devices, photomultiplier tubes , and video camera tubes . Nevertheless, germanium , rubidium, selenium, silicon, tellurium, and several other elements can be substituted for caesium in photosensitive materials. Caesium iodide (CsI), bromide (CsBr) and fluoride (CsF) crystals are employed for scintillators in scintillation counters widely used in mineral exploration and particle physics research to detect gamma and X-ray radiation. Being

2550-452: Is usually measured in kilohertz (kHz), megahertz (MHz), or gigahertz (GHz). with the latter known as microwaves . Light is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens of terahertz (THz, infrared ) to a few petahertz (PHz, ultraviolet ), with the visible spectrum being 400–790 THz. Electromagnetic radiation with frequencies in the low terahertz range (intermediate between those of

2635-634: The National Physical Laboratory in the UK. Caesium clocks have improved over the past half-century and are regarded as "the most accurate realization of a unit that mankind has yet achieved." These clocks measure frequency with an error of 2 to 3 parts in 10 , which corresponds to an accuracy of 2  nanoseconds per day, or one second in 1.4 million years. The latest versions are more accurate than 1 part in 10 , about 1 second in 20 million years. The caesium standard

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2720-403: The beta decay of originally more neutron-rich fission products, passing through various isotopes of iodine and xenon . Because iodine and xenon are volatile and can diffuse through nuclear fuel or air, radioactive caesium is often created far from the original site of fission. With nuclear weapons testing in the 1950s through the 1980s, Cs was released into the atmosphere and returned to

2805-400: The electrical conductivity . Caesium was not recognized as a high-performance industrial metal until the 1950s. Applications for nonradioactive caesium included photoelectric cells , photomultiplier tubes, optical components of infrared spectrophotometers , catalysts for several organic reactions, crystals for scintillation counters , and in magnetohydrodynamic power generators . Caesium

2890-415: The extractive oil industry . Aqueous solutions of caesium formate (HCOO Cs )—made by reacting caesium hydroxide with formic acid —were developed in the mid-1990s for use as oil well drilling and completion fluids . The function of a drilling fluid is to lubricate drill bits, to bring rock cuttings to the surface, and to maintain pressure on the formation during drilling of the well. Completion fluids assist

2975-403: The ground state of caesium-133 . The 13th General Conference on Weights and Measures of 1967 defined a second as: "the duration of 9,192,631,770 cycles of microwave light absorbed or emitted by the hyperfine transition of caesium-133 atoms in their ground state undisturbed by external fields". The largest present-day use of nonradioactive caesium is in caesium formate drilling fluids for

3060-496: The ozonide CsO 3 , several brightly coloured suboxides have also been studied. These include Cs 7 O , Cs 4 O , Cs 11 O 3 , Cs 3 O (dark-green ), CsO, Cs 3 O 2 , as well as Cs 7 O 2 . The latter may be heated in a vacuum to generate Cs 2 O . Binary compounds with sulfur , selenium , and tellurium also exist. Caesium has 41 known isotopes , ranging in mass number (i.e. number of nucleons in

3145-404: The superoxide CsO 2 is the main product. The "normal" caesium oxide ( Cs 2 O ) forms yellow-orange hexagonal crystals, and is the only oxide of the anti- CdCl 2 type. It vaporizes at 250 °C (482 °F), and decomposes to caesium metal and the peroxide Cs 2 O 2 at temperatures above 400 °C (752 °F). In addition to the superoxide and

3230-449: The 0.1–10 Hz range. In computers, most central processing units (CPU) are labeled in terms of their clock rate expressed in megahertz ( MHz ) or gigahertz ( GHz ). This specification refers to the frequency of the CPU's master clock signal . This signal is nominally a square wave , which is an electrical voltage that switches between low and high logic levels at regular intervals. As

3315-468: The 1970s. In some usage, the "per second" was omitted, so that "megacycles" (Mc) was used as an abbreviation of "megacycles per second" (that is, megahertz (MHz)). Sound is a traveling longitudinal wave , which is an oscillation of pressure . Humans perceive the frequency of a sound as its pitch . Each musical note corresponds to a particular frequency. An infant's ear is able to perceive frequencies ranging from 20 Hz to 20 000  Hz ;

3400-412: The 1990s, the largest application of the element has been as caesium formate for drilling fluids , but it has a range of applications in the production of electricity, in electronics, and in chemistry. The radioactive isotope caesium-137 has a half-life of about 30 years and is used in medical applications, industrial gauges, and hydrology. Nonradioactive caesium compounds are only mildly toxic , but

3485-582: The DS0 rate may support twenty 2.4 kbit/s channels, ten 4.8 kbit/s channels, five 9.67 kbit/s channels, one 56 kbit/s channel, or one 64 kbit/s clear channel. E0 (standardized as ITU G.703 ) is the European equivalent of the North American DS0 for carrying a single voice call. However, there are some subtle differences in implementation. Voice signals are encoded for carriage over E0 according to ITU G.711 . Note that when

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3570-554: The anion itself is coloured. Many of the simple salts are hygroscopic , but less so than the corresponding salts of lighter alkali metals. The phosphate , acetate , carbonate , halides , oxide , nitrate , and sulfate salts are water-soluble. Its double salts are often less soluble, and the low solubility of caesium aluminium sulfate is exploited in refining Cs from ores. The double salts with antimony (such as CsSbCl 4 ), bismuth , cadmium , copper , iron , and lead are also poorly soluble . Caesium hydroxide (CsOH)

3655-476: The average adult human can hear sounds between 20 Hz and 16 000  Hz . The range of ultrasound , infrasound and other physical vibrations such as molecular and atomic vibrations extends from a few femtohertz into the terahertz range and beyond. Electromagnetic radiation is often described by its frequency—the number of oscillations of the perpendicular electric and magnetic fields per second—expressed in hertz. Radio frequency radiation

3740-582: The basis of the Brønsted–Lowry acid–base theory . A stoichiometric mixture of caesium and gold will react to form yellow caesium auride (Cs Au ) upon heating. The auride anion here behaves as a pseudohalogen . The compound reacts violently with water, yielding caesium hydroxide , metallic gold, and hydrogen gas; in liquid ammonia it can be reacted with a caesium-specific ion exchange resin to produce tetramethylammonium auride . The analogous platinum compound, red caesium platinide ( Cs 2 Pt ), contains

3825-447: The caesium-133 atom, to be 9 192 631 770 when expressed in the unit Hz , which is equal to s ." Caesium vapour thermionic generators are low-power devices that convert heat energy to electrical energy. In the two-electrode vacuum tube converter, caesium neutralizes the space charge near the cathode and enhances the current flow. Caesium is also important for its photoemissive properties, converting light to electron flow. It

3910-487: The case of periodic events. It is named after Heinrich Rudolf Hertz (1857–1894), the first person to provide conclusive proof of the existence of electromagnetic waves . For high frequencies, the unit is commonly expressed in multiples : kilohertz (kHz), megahertz (MHz), gigahertz (GHz), terahertz (THz). Some of the unit's most common uses are in the description of periodic waveforms and musical tones , particularly those used in radio - and audio-related applications. It

3995-466: The components of many other heavy liquids, caesium formate is relatively environment-friendly. Caesium formate brine can be blended with potassium and sodium formates to decrease the density of the fluids to that of water (1.0 g/cm , or 8.3 pounds per gallon). Furthermore, it is biodegradable and may be recycled, which is important in view of its high cost (about $ 4,000 per barrel in 2001). Alkali formates are safe to handle and do not damage

4080-498: The cube, while the caesium atoms lie in the holes in the centre of the cubes. This structure is shared with CsBr and CsI , and many other compounds that do not contain Cs. In contrast, most other alkaline halides have the sodium chloride (NaCl) structure. The CsCl structure is preferred because Cs has an ionic radius of 174  pm and Cl 181 pm. More so than the other alkali metals, caesium forms numerous binary compounds with oxygen . When caesium burns in air,

4165-406: The currently accepted one of 132.9). They tried to generate elemental caesium by electrolysis of molten caesium 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"; as a result, they assigned it as a subchloride ( Cs 2 Cl ). In reality, the product was probably

4250-528: The decreasing frequency of light required to excite electrons of the alkali metals as the group is descended. For lithium through rubidium this frequency is in the ultraviolet, but for caesium it enters the blue–violet end of the spectrum; in other words, the plasmonic frequency of the alkali metals becomes lower from lithium to caesium. Thus caesium transmits and partially absorbs violet light preferentially while other colours (having lower frequency) are reflected; hence it appears yellowish. Its compounds burn with

4335-454: The developing market, Cabot Corporation built a production plant in 1997 at the Tanco mine near Bernic Lake in Manitoba , with a capacity of 12,000 barrels (1,900 m ) per year of caesium formate solution. The primary smaller-scale commercial compounds of caesium are caesium chloride and nitrate . Alternatively, caesium metal may be obtained from the purified compounds derived from

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4420-441: The emplacement of control hardware after drilling but prior to production by maintaining the pressure. The high density of the caesium formate brine (up to 2.3 g/cm , or 19.2 pounds per gallon), coupled with the relatively benign nature of most caesium compounds, reduces the requirement for toxic high-density suspended solids in the drilling fluid—a significant technological, engineering and environmental advantage. Unlike

4505-440: The event being counted may be a complete cycle); 100 Hz means "one hundred periodic events occur per second", and so on. The unit may be applied to any periodic event—for example, a clock might be said to tick at 1 Hz , or a human heart might be said to beat at 1.2 Hz . The occurrence rate of aperiodic or stochastic events is expressed in reciprocal second or inverse second (1/s or s ) in general or, in

4590-449: The hertz has become the primary unit of measurement accepted by the general populace to determine the performance of a CPU, many experts have criticized this approach, which they claim is an easily manipulable benchmark . Some processors use multiple clock cycles to perform a single operation, while others can perform multiple operations in a single cycle. For personal computers, CPU clock speeds have ranged from approximately 1 MHz in

4675-432: The hexachloroplatinate with hydrogen , caesium and rubidium were separated by the difference in solubility of their carbonates in alcohol. The process yielded 9.2 grams (0.32 oz) of rubidium chloride and 7.3 grams (0.26 oz) of caesium chloride from the initial 44,000 litres of mineral water. From the caesium chloride, the two scientists estimated the atomic weight of the new element at 123.35 (compared to

4760-413: The highest normally usable radio frequencies and long-wave infrared light) is often called terahertz radiation . Even higher frequencies exist, such as that of X-rays and gamma rays , which can be measured in exahertz (EHz). For historical reasons, the frequencies of light and higher frequency electromagnetic radiation are more commonly specified in terms of their wavelengths or photon energies : for

4845-452: The inner 5p electrons could form chemical bonds, where caesium would behave as the seventh 5p element, suggesting that higher caesium fluorides with caesium in oxidation states from +2 to +6 could exist under such conditions. Some slight differences arise from the fact that it has a higher atomic mass and is more electropositive than other (nonradioactive) alkali metals. Caesium is the most electropositive chemical element. The caesium ion

4930-508: The insoluble double salt directly as caesium alum ( CsAl(SO 4 ) 2 ·12H 2 O ). The aluminium sulfate component is converted to insoluble aluminium oxide by roasting the alum with carbon , and the resulting product is leached with water to yield a Cs 2 SO 4 solution. Roasting pollucite with calcium carbonate and calcium chloride yields insoluble calcium silicates and soluble caesium chloride. Leaching with water or dilute ammonia ( NH 4 OH ) yields

5015-459: The late 1970s ( Atari , Commodore , Apple computers ) to up to 6 GHz in IBM Power microprocessors . Various computer buses , such as the front-side bus connecting the CPU and northbridge , also operate at various frequencies in the megahertz range. Higher frequencies than the International System of Units provides prefixes for are believed to occur naturally in the frequencies of

5100-405: The lowest and highest electronegativities , respectively, among all the known elements. Caesium chloride (CsCl) crystallizes in the simple cubic crystal system . Also called the "caesium chloride structure", this structural motif is composed of a primitive cubic lattice with a two-atom basis, each with an eightfold coordination ; the chloride atoms lie upon the lattice points at the edges of

5185-485: The more widespread rhodizite . The only economically important ore for caesium is pollucite Cs(AlSi 2 O 6 ) , which is found in a few places around the world in zoned pegmatites, associated with the more commercially important lithium minerals, lepidolite and petalite . Within the pegmatites, the large grain size and the strong separation of the minerals results in high-grade ore for mining. The world's most significant and richest known source of caesium

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5270-405: The newly developed method of flame spectroscopy . The first small-scale applications for caesium were as a " getter " in vacuum tubes and in photoelectric cells . Caesium is widely used in highly accurate atomic clocks . In 1967, the International System of Units began using a specific hyperfine transition of neutral caesium-133 atoms to define the basic unit of time, the second . Since

5355-525: The nucleus) from 112 to 152. Several of these are synthesized from lighter elements by the slow neutron capture process ( S-process ) inside old stars and by the R-process in supernova explosions. The only stable caesium isotope is Cs, with 78 neutrons . Although it has a large nuclear spin ( ⁠ 7 / 2 ⁠ +), nuclear magnetic resonance studies can use this isotope at a resonating frequency of 11.7  MHz . The radioactive Cs has

5440-486: The number of wires required between two involved in exchanging voice calls, a system was built in which multiple DS0s are multiplexed together on higher capacity circuits. In this system, twenty-four (24) DS0s are multiplexed into a DS1 signal. Twenty-eight (28) DS1s are multiplexed into a DS3 . When carried over copper wire, this is the well-known T-carrier system, with T1 and T3 corresponding to DS1 and DS3, respectively. Besides its use for voice communications,

5525-776: The ore. Caesium chloride and the other caesium halides can be reduced at 700 to 800 °C (1,292 to 1,472 °F) with calcium or barium , and caesium metal distilled from the result. In the same way, the aluminate, carbonate, or hydroxide may be reduced by magnesium . The metal can also be isolated by electrolysis of fused caesium cyanide (CsCN). Exceptionally pure and gas-free caesium can be produced by 390 °C (734 °F) thermal decomposition of caesium azide CsN 3 , which can be produced from aqueous caesium sulfate and barium azide . In vacuum applications, caesium dichromate can be reacted with zirconium to produce pure caesium metal without other gaseous products. The price of 99.8% pure caesium (metal basis) in 2009

5610-414: The original on 2022-01-22. KHz The hertz (symbol: Hz ) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle ) per second . The hertz is an SI derived unit whose formal expression in terms of SI base units is s , meaning that one hertz is one per second or the reciprocal of one second . It is used only in

5695-412: The other alkali metals (except lithium); the alloy with a molar distribution of 41% caesium, 47% potassium , and 12% sodium has the lowest melting point of any known metal alloy, at −78 °C (−108 °F). A few amalgams have been studied: CsHg 2 is black with a purple metallic lustre , while CsHg is golden-coloured, also with a metallic lustre. The golden colour of caesium comes from

5780-410: The other isotopes have half-lives from a few seconds to fractions of a second. At least 21 metastable nuclear isomers exist. Other than Cs (with a half-life of just under 3 hours), all are very unstable and decay with half-lives of a few minutes or less. The isotope Cs is one of the long-lived fission products of uranium produced in nuclear reactors . However, this fission product yield

5865-478: The platinide ion that behaves as a pseudo chalcogen . Like all metal cations, Cs forms complexes with Lewis bases in solution. Because of its large size, Cs usually adopts coordination numbers greater than 6, the number typical for the smaller alkali metal cations. This difference is apparent in the 8-coordination of CsCl. This high coordination number and softness (tendency to form covalent bonds) are properties exploited in separating Cs from other cations in

5950-529: The presence of trace amounts of oxygen . When in the presence of mineral oil (where it is best kept during transport), it loses its metallic lustre and takes on a duller, grey appearance. It has a melting point of 28.5 °C (83.3 °F), making it one of the few elemental metals that are liquid near room temperature . The others are rubidium (39 °C [102 °F]), francium (estimated at 27 °C [81 °F]), mercury (−39 °C [−38 °F]), and gallium (30 °C [86 °F]); bromine

6035-512: The prime sources of radioactivity from spent nuclear fuel after several years of cooling, lasting several hundred years. Those two isotopes are the largest source of residual radioactivity in the area of the Chernobyl disaster . Because of the low capture rate, disposing of Cs through neutron capture is not feasible and the only current solution is to allow it to decay over time. Almost all caesium produced from nuclear fission comes from

6120-414: The problems with the chloride. Historically, the most important use for caesium has been in research and development, primarily in chemical and electrical fields. Very few applications existed for caesium until the 1920s, when it came into use in radio vacuum tubes , where it had two functions; as a getter , it removed excess oxygen after manufacture, and as a coating on the heated cathode , it increased

6205-425: The producing formation or downhole metals as corrosive alternative, high-density brines (such as zinc bromide ZnBr 2 solutions) sometimes do; they also require less cleanup and reduce disposal costs. Caesium-based atomic clocks use the electromagnetic transitions in the hyperfine structure of caesium-133 atoms as a reference point. The first accurate caesium clock was built by Louis Essen in 1955 at

6290-517: The pure metal's tendency to react explosively with water means that caesium is considered a hazardous material, and the radioisotopes present a significant health and environmental hazard. Caesium is the spelling recommended by the International Union of Pure and Applied Chemistry (IUPAC). The American Chemical Society (ACS) has used the spelling cesium since 1921, following Webster's New International Dictionary . The element

6375-806: The quantum-mechanical vibrations of massive particles, although these are not directly observable and must be inferred through other phenomena. By convention, these are typically not expressed in hertz, but in terms of the equivalent energy, which is proportional to the frequency by the factor of the Planck constant . The CJK Compatibility block in Unicode contains characters for common SI units for frequency. These are intended for compatibility with East Asian character encodings, and not for use in new documents (which would be expected to use Latin letters, e.g. "MHz"). Caesium Caesium ( IUPAC spelling; also spelled cesium in American English )

6460-438: The remediation of nuclear wastes, where Cs must be separated from large amounts of nonradioactive K . Caesium fluoride (CsF) is a hygroscopic white solid that is widely used in organofluorine chemistry as a source of fluoride anions. Caesium fluoride has the halite structure, which means that the Cs and F pack in a cubic closest packed array as do Na and Cl in sodium chloride . Notably, caesium and fluorine have

6545-564: The rules for capitalisation of a common noun ; i.e., hertz becomes capitalised at the beginning of a sentence and in titles but is otherwise in lower case. The hertz is named after the German physicist Heinrich Hertz (1857–1894), who made important scientific contributions to the study of electromagnetism . The name was established by the International Electrotechnical Commission (IEC) in 1935. It

6630-409: The second as "the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium -133 atom" and then adds: "It follows that the hyperfine splitting in the ground state of the caesium 133 atom is exactly 9 192 631 770  hertz , ν hfs Cs = 9 192 631 770  Hz ." The dimension of the unit hertz

6715-495: The solution. After conversion to the nitrates and extraction with ethanol , a sodium-free mixture was obtained. From this mixture, the lithium was precipitated by ammonium carbonate . Potassium, rubidium, and caesium form insoluble salts with chloroplatinic acid , but these salts show a slight difference in solubility in hot water, and the less-soluble caesium and rubidium hexachloroplatinate ( (Cs,Rb) 2 PtCl 6 ) were obtained by fractional crystallization . After reduction of

6800-413: The specific case of radioactivity , in becquerels . Whereas 1 Hz (one per second) specifically refers to one cycle (or periodic event) per second, 1 Bq (also one per second) specifically refers to one radionuclide event per second on average. Even though frequency, angular velocity , angular frequency and radioactivity all have the dimension T , of these only frequency is expressed using

6885-516: The surface of the earth as a component of radioactive fallout . It is a ready marker of the movement of soil and sediment from those times. Caesium is a relatively rare element, estimated to average 3  parts per million in the Earth's crust . It is the 45th most abundant element and 36th among the metals. Caesium is 30 times less abundant than rubidium , with which it is closely associated, chemically. Due to its large ionic radius , caesium

6970-480: The unit hertz. Thus a disc rotating at 60 revolutions per minute (rpm) is said to have an angular velocity of 2 π  rad/s and a frequency of rotation of 1 Hz . The correspondence between a frequency f with the unit hertz and an angular velocity ω with the unit radians per second is The hertz is named after Heinrich Hertz . As with every SI unit named for a person, its symbol starts with an upper case letter (Hz), but when written in full, it follows

7055-452: Was about $ 10 per gram ($ 280/oz), but the compounds are significantly cheaper. In 1860, Robert Bunsen and Gustav Kirchhoff discovered caesium in the mineral water from Dürkheim , Germany. Because of the bright blue lines in the emission spectrum , they derived the name from the Latin word caesius , meaning ' bluish grey ' . Caesium was the first element to be discovered with

7140-490: Was adopted by the General Conference on Weights and Measures (CGPM) ( Conférence générale des poids et mesures ) in 1960, replacing the previous name for the unit, "cycles per second" (cps), along with its related multiples, primarily "kilocycles per second" (kc/s) and "megacycles per second" (Mc/s), and occasionally "kilomegacycles per second" (kMc/s). The term "cycles per second" was largely replaced by "hertz" by

7225-494: Was named after the Latin word caesius , meaning "bluish grey". In medieval and early modern writings caesius was spelled with the ligature æ as cæsius ; hence, an alternative but now old-fashioned orthography is cæsium . More spelling explanation at ae/oe vs e . Of all elements that are solid at room temperature, caesium is the softest: it has a hardness of 0.2 Mohs . It is a very ductile , pale metal, which darkens in

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