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54-446: Caesium chloride is widely used in isopycnic centrifugation for separating various types of DNA . It is a reagent in analytical chemistry , where it is used to identify ions by the color and morphology of the precipitate. When enriched in radioisotopes , such as CsCl or CsCl, caesium chloride is used in nuclear medicine applications such as treatment of cancer and diagnosis of myocardial infarction . Another form of cancer treatment

108-438: A cavity must form in the solvent to make space for a solute. This is both entropically and enthalpically unfavorable, as solvent ordering increases and solvent-solvent interactions decrease. Stronger interactions among solvent molecules leads to a greater enthalpic penalty for cavity formation. Next, a particle of solute must separate from the bulk. This is enthalpically unfavorable since solute-solute interactions decrease, but when

162-427: A concentration: mass per volume (mg/mL), molarity (mol/L), etc. Solvation involves different types of intermolecular interactions: Which of these forces are at play depends on the molecular structure and properties of the solvent and solute. The similarity or complementary character of these properties between solvent and solute determines how well a solute can be solvated by a particular solvent. Solvent polarity

216-409: A favorable change in the interactions between the protein and the surrounding water molecules. Folded proteins are stabilized by 5-10 kcal/mol relative to the unfolded state due to a combination of solvation and the stronger intramolecular interactions in the folded protein structure , including hydrogen bonding . Minimizing the number of hydrophobic side chains exposed to water by burying them in

270-544: A hydrogen bond are called aprotic. H-bond donor ability is classified on a scale (α). Protic solvents can solvate solutes that can accept hydrogen bonds. Similarly, solvents that can accept a hydrogen bond can solvate H-bond-donating solutes. The hydrogen bond acceptor ability of a solvent is classified on a scale (β). Solvents such as water can both donate and accept hydrogen bonds, making them excellent at solvating solutes that can donate or accept (or both) H-bonds. Some chemical compounds experience solvatochromism , which

324-478: A major contribution from CsCl, were being produced annually around the 1970s and 2000s worldwide. Caesium chloride enriched with caesium-137 for radiation therapy applications is produced at a single facility Mayak in the Ural Region of Russia and is sold internationally through a UK dealer. The salt is synthesized at 200 °C because of its hygroscopic nature and sealed in a thimble-shaped steel container which

378-453: A primitive cubic lattice with a two-atom basis, where both atoms have eightfold coordination. The chloride atoms lie upon the lattice points at the corners of the cube, while the caesium atoms lie in the holes in the center of the cubes; an alternative and exactly equivalent 'setting' has the caesium ions at the corners and the chloride ion in the center. This structure is shared with CsBr and CsI and many binary metallic alloys . In contrast,

432-563: A relatively high solubility in formic acid (1077 g/L at 18 °C) and hydrazine ; medium solubility in methanol (31.7 g/L at 25 °C) and low solubility in ethanol (7.6 g/L at 25 °C), sulfur dioxide (2.95 g/L at 25 °C), ammonia (3.8 g/L at 0 °C), acetone (0.004% at 18 °C), acetonitrile (0.083 g/L at 18 °C), ethylacetate and other complex ethers , butanone , acetophenone , pyridine and chlorobenzene . Despite its wide band gap of about 8.35 eV at 80 K, caesium chloride weakly conducts electricity, and

486-403: A solution depends on the solvation of its ions. Nonpolar solvents cannot solvate ions, and ions will be found as ion pairs. Hydrogen bonding among solvent and solute molecules depends on the ability of each to accept H-bonds, donate H-bonds, or both. Solvents that can donate H-bonds are referred to as protic, while solvents that do not contain a polarized bond to a hydrogen atom and cannot donate

540-414: A solution with high density and yet relatively low viscosity, and CsCl suits it because of its high solubility in water, high density owing to the large mass of Cs, as well as low viscosity and high stability of CsCl solutions. The sample is put on top of the solution, and then the tube is spun at a very high speed for an extended time, at times lasting days. The CsCl molecules become densely packed toward

594-441: A solution with high density and yet relatively low viscosity, and CsCl suits it because of its high solubility in water, high density owing to the large mass of Cs, as well as low viscosity and high stability of CsCl solutions. Caesium chloride is rarely used in organic chemistry. It can act as a phase transfer catalyst reagent in selected reactions. One of these reactions is the synthesis of glutamic acid derivatives where TBAB

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648-402: A source containing about 93 grams of CsCl, was stolen from an abandoned hospital and forced open by two scavengers. The blue glow emitted in the dark by the radioactive caesium chloride attracted the thieves and their relatives who were unaware of the associated dangers and spread the powder. This resulted in one of the worst radiation spill accidents in which 4 people died within a month from

702-440: A surface of ion-exchange resin . Solvation is, in concept, distinct from solubility . Solvation or dissolution is a kinetic process and is quantified by its rate. Solubility quantifies the dynamic equilibrium state achieved when the rate of dissolution equals the rate of precipitation . The consideration of the units makes the distinction clearer. The typical unit for dissolution rate is mol/s. The units for solubility express

756-423: A variety of double salts with other chlorides. Examples include 2CsCl·BaCl 2 , 2CsCl·CuCl 2 , CsCl·2CuCl and CsCl·LiCl, and with interhalogen compounds: Caesium chloride occurs naturally as an impurity in the halide minerals carnallite (KMgCl 3 ·6H 2 O with up to 0.002% CsCl), sylvite (KCl) and kainite (MgSO 4 ·KCl·3H 2 O), and in mineral waters. For example, the water of Bad Dürkheim spa, which

810-471: Is 2300 mg per kilogram of body weight for oral administration and 910 mg/kg for intravenous injection. The mild toxicity of CsCl is related to its ability to lower the concentration of potassium in the body and partly substitute it in biochemical processes. When taken in large quantities, however, can cause a significant imbalance in potassium and lead to hypokalemia , arrhythmia , and acute cardiac arrest . However, caesium chloride powder can irritate

864-405: Is a stub . You can help Misplaced Pages by expanding it . Solvation Solvation describes the interaction of a solvent with dissolved molecules. Both ionized and uncharged molecules interact strongly with a solvent, and the strength and nature of this interaction influence many properties of the solute, including solubility, reactivity, and color, as well as influencing the properties of

918-453: Is a change in color due to solvent polarity. This phenomenon illustrates how different solvents interact differently with the same solute. Other solvent effects include conformational or isomeric preferences and changes in the acidity of a solute. The solvation process will be thermodynamically favored only if the overall Gibbs energy of the solution is decreased, compared to the Gibbs energy of

972-465: Is an interaction of a solute with the solvent , which leads to stabilization of the solute species in the solution . In the solvated state, an ion or molecule in a solution is surrounded or complexed by solvent molecules. Solvated species can often be described by coordination number , and the complex stability constants . The concept of the solvation interaction can also be applied to an insoluble material, for example, solvation of functional groups on

1026-546: Is apparent that they are not solvated. Strong solvent–solute interactions make the process of solvation more favorable. One way to compare how favorable the dissolution of a solute is in different solvents is to consider the free energy of transfer. The free energy of transfer quantifies the free energy difference between dilute solutions of a solute in two different solvents. This value essentially allows for comparison of solvation energies without including solute-solute interactions. In general, thermodynamic analysis of solutions

1080-440: Is called the cybotactic region. Water is the most common and well-studied polar solvent, but others exist, such as ethanol , methanol , acetone , acetonitrile , and dimethyl sulfoxide . Polar solvents are often found to have a high dielectric constant , although other solvent scales are also used to classify solvent polarity. Polar solvents can be used to dissolve inorganic or ionic compounds such as salts. The conductivity of

1134-407: Is done by modeling them as reactions. For example, if you add sodium chloride to water, the salt will dissociate into the ions sodium(+aq) and chloride(-aq). The equilibrium constant for this dissociation can be predicted by the change in Gibbs energy of this reaction. The Born equation is used to estimate Gibbs free energy of solvation of a gaseous ion. Recent simulation studies have shown that

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1188-417: Is due to favorable van der Waals interactions and intramolecular electrostatic interactions which would be dampened in the presence of a solvent. As computer power increased, it became possible to try and incorporate the effects of solvation within a simulation and the simplest way to do this is to surround the molecule being simulated with a "skin" of solvent molecules, akin to simulating the molecule within

1242-452: Is necessary to release an ion from its lattice and the energy given off when it combines with a solvent molecule is called the enthalpy change of solution . A negative value for the enthalpy change of solution corresponds to an ion that is likely to dissolve, whereas a high positive value means that solvation will not occur. It is possible that an ion will dissolve even if it has a positive enthalpy value. The extra energy required comes from

1296-483: Is tetrabutylammonium bromide (interphase catalyst) and CPME is a cyclopentyl methyl ether (solvent). Another reaction is substitution of tetranitromethane where DMF is dimethylformamide (solvent). Caesium chloride is a reagent in traditional analytical chemistry used for detecting inorganic ions via the color and morphology of the precipitates. Quantitative concentration measurement of some of these ions, e.g. Mg, with inductively coupled plasma mass spectrometry ,

1350-620: Is the change in enthalpy minus the product of temperature (in Kelvin ) times the change in entropy. Gases have a negative entropy of solution, due to the decrease in gaseous volume as gas dissolves. Since their enthalpy of solution does not decrease too much with temperature, and their entropy of solution is negative and does not vary appreciably with temperature, most gases are less soluble at higher temperatures. Enthalpy of solvation can help explain why solvation occurs with some ionic lattices but not with others. The difference in energy between that which

1404-473: Is the most important factor in determining how well it solvates a particular solute. Polar solvents have molecular dipoles, meaning that part of the solvent molecule has more electron density than another part of the molecule. The part with more electron density will experience a partial negative charge while the part with less electron density will experience a partial positive charge. Polar solvent molecules can solvate polar solutes and ions because they can orient

1458-424: Is the process of reorganizing solvent and solute molecules into solvation complexes and involves bond formation, hydrogen bonding , and van der Waals forces . Solvation of a solute by water is called hydration. Solubility of solid compounds depends on a competition between lattice energy and solvation, including entropy effects related to changes in the solvent structure. By an IUPAC definition, solvation

1512-432: Is then enclosed into another steel casing. The sealing is required to protect the salt from moisture. In the laboratory, CsCl can be obtained by treating caesium hydroxide , carbonate , caesium bicarbonate, or caesium sulfide with hydrochloric acid: Caesium chloride is the main precursor to caesium metal by high-temperature reduction: A similar reaction – heating CsCl with calcium in vacuum in presence of phosphorus –

1566-401: Is used in the preparation of electrically conducting glasses and screens of cathode ray tubes. In conjunction with rare gases CsCl is used in excimer lamps and excimer lasers . Other uses include activation of electrodes in welding; manufacture of mineral water, beer and drilling muds ; and high-temperature solders. High-quality CsCl single crystals have a wide transparency range from UV to

1620-404: Is used to evaluate the hardness of water. It is also used for detection of the following ions: The American Cancer Society states that "available scientific evidence does not support claims that non-radioactive cesium chloride supplements have any effect on tumors." The Food and Drug Administration has warned about safety risks, including significant heart toxicity and death, associated with

1674-476: The Meselson-Stahl experiment . Buoyant density of the majority of DNA is 1.7g/cm which is equal to the density of 6M CsCl solution. Buoyant density of DNA changes with its GC content . The term " satellite DNA " refers to small bands of repetitive DNA sequences with distinct base composition floating above (A+T rich) or below (G+C rich) the main component DNA. This article about analytical chemistry

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1728-520: The mucous membranes and cause asthma . Because of its high solubility in water, caesium chloride is highly mobile and can even diffuse through concrete. This is a drawback for its radioactive form which urges a search for less chemically mobile radioisotope materials. Commercial sources of radioactive caesium chloride are well sealed in a double steel enclosure. However, in the Goiânia accident in Brazil , such

1782-434: The appropriate partially charged portion of the molecule towards the solute through electrostatic attraction. This stabilizes the system and creates a solvation shell (or hydration shell in the case of water) around each particle of solute. The solvent molecules in the immediate vicinity of a solute particle often have a much different ordering than the rest of the solvent, and this area of differently ordered solvent molecules

1836-493: The bottom, so a continuous gradient of layers of different densities (and CsCl concentrations) form. Since the original solution was approximately the same density, they go to a level where their density and the CsCl density are the same, to which they form a sharp, distinctive band. This method very sharply separates molecules, and is so sharp that it can even separate different molecular isotopes from one another. It has been utilized in

1890-399: The center of a folded protein is a driving force related to solvation. Solvation also affects host–guest complexation . Many host molecules have a hydrophobic pore that readily encapsulates a hydrophobic guest. These interactions can be used in applications such as drug delivery, such that a hydrophobic drug molecule can be delivered in a biological system without needing to covalently modify

1944-488: The conductivity is not electronic but ionic . The conductivity has a value of the order 10 S/cm at 300 °C. It occurs through nearest-neighbor jumps of lattice vacancies, and the mobility is much higher for the Cl than Cs vacancies. The conductivity increases with temperature up to about 450 °C, with an activation energy changing from 0.6 to 1.3 eV at about 260 °C. It then sharply drops by two orders of magnitude because of

1998-403: The double salt with hydrogen sulfide gives CsCl: High-purity CsCl is also produced from recrystallized Cs [ ICl 2 ] {\displaystyle {\ce {Cs[ICl2]}}} (and Cs [ ICl 4 ] {\displaystyle {\ce {Cs[ICl4]}}} ) by thermal decomposition: Only about 20 tonnes of caesium compounds, with

2052-581: The drug in order to solubilize it. Binding constants for host–guest complexes depend on the polarity of the solvent. Hydration affects electronic and vibrational properties of biomolecules. Due to the importance of the effects of solvation on the structure of macromolecules, early computer simulations which attempted to model their behaviors without including the effects of solvent ( in vacuo ) could yield poor results when compared with experimental data obtained in solution. Small molecules may also adopt more compact conformations when simulated in vacuo ; this

2106-407: The event of an accident. For instance, radiothermal generators (RTGs) often use strontium titanate , which is insoluble in water. For teletherapy sources, however, the radioactive density ( Ci in a given volume) needs to be very high, which is not possible with known insoluble caesium compounds. A thimble-shaped container of radioactive caesium chloride provides the active source. Caesium chloride

2160-517: The exposure, 20 showed signs of radiation sickness , 249 people were contaminated with radioactive caesium chloride, and about a thousand received a dose exceeding a yearly amount of background radiation. More than 110,000 people overwhelmed the local hospitals, and several city blocks had to be demolished in the cleanup operations. In the first days of the contamination, stomach disorders and nausea due to radiation sickness were experienced by several people, but only after several days one person associated

2214-594: The increase in entropy that results when the ion dissolves. The introduction of entropy makes it harder to determine by calculation alone whether a substance will dissolve or not. A quantitative measure for solvation power of solvents is given by donor numbers . Although early thinking was that a higher ratio of a cation's ion charge to ionic radius , or the charge density, resulted in more solvation, this does not stand up to scrutiny for ions like iron(III) or lanthanides and actinides , which are readily hydrolyzed to form insoluble (hydrous) oxides. As these are solids, it

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2268-468: The infrared and therefore had been used for cuvettes, prisms and windows in optical spectrometers; this use was discontinued with the development of less hygroscopic materials. CsCl is a potent inhibitor of HCN channels, which carry the h-current in excitable cells such as neurons. Therefore, it can be useful in electrophysiology experiments in neuroscience. Caesium chloride has a low toxicity to humans and animals. Its median lethal dose (LD 50 ) in mice

2322-408: The other alkaline halides have the sodium chloride (rocksalt) structure. When both ions are similar in size (Cs ionic radius 174 pm for this coordination number, Cl 181 pm) the CsCl structure is adopted, when they are different (Na ionic radius 102 pm, Cl 181 pm) the sodium chloride structure is adopted. Upon heating to above 445 °C, the normal caesium chloride structure (α-CsCl) converts to

2376-543: The phase transition from the α-CsCl to β-CsCl phase. The conductivity is also suppressed by application of pressure (about 10 times decrease at 0.4 GPa) which reduces the mobility of lattice vacancies. Caesium chloride completely dissociates upon dissolution in water, and the Cs cations are solvated in dilute solution. CsCl converts to caesium sulfate upon being heated in concentrated sulfuric acid or heated with caesium hydrogen sulfate at 550–700 °C: Caesium chloride forms

2430-435: The separated solvent and solid (or gas or liquid). This means that the change in enthalpy minus the change in entropy (multiplied by the absolute temperature) is a negative value, or that the Gibbs energy of the system decreases. A negative Gibbs energy indicates a spontaneous process but does not provide information about the rate of dissolution. Solvation involves multiple steps with different energy consequences. First,

2484-470: The solute particle enters the cavity, the resulting solvent-solute interactions are enthalpically favorable. Finally, as solute mixes into solvent, there is an entropy gain. [REDACTED] The enthalpy of solution is the solution enthalpy minus the enthalpy of the separate systems, whereas the entropy of solution is the corresponding difference in entropy . The solvation energy (change in Gibbs free energy )

2538-427: The solvent such as its viscosity and density. If the attractive forces between the solvent and solute particles are greater than the attractive forces holding the solute particles together, the solvent particles pull the solute particles apart and surround them. The surrounded solute particles then move away from the solid solute and out into the solution. Ions are surrounded by a concentric shell of solvent . Solvation

2592-482: The symptoms with the powder and brought a sample to the authorities. Isopycnic centrifugation Buoyant density centrifugation (also isopycnic centrifugation or equilibrium density-gradient centrifugation ) uses the concept of buoyancy to separate molecules in solution by their differences in density. Historically a cesium chloride (CsCl) solution was often used, but more commonly used density gradients are sucrose or Percoll . This application requires

2646-407: The use of cesium chloride in naturopathic medicine. Caesium chloride composed of radioisotopes such as CsCl and CsCl, is used in nuclear medicine , including treatment of cancer ( brachytherapy ) and diagnosis of myocardial infarction . In the production of radioactive sources, it is normal to choose a chemical form of the radioisotope which would not be readily dispersed in the environment in

2700-587: The variation in solvation energy between the ions and the surrounding water molecules underlies the mechanism of the Hofmeister series . Solvation (specifically, hydration ) is important for many biological structures and processes. For instance, solvation of ions and/or of charged macromolecules, like DNA and proteins, in aqueous solutions influences the formation of heterogeneous assemblies, which may be responsible for biological function. As another example, protein folding occurs spontaneously, in part because of

2754-705: The β-CsCl form with the rocksalt structure ( space group Fm 3 m ). The rocksalt structure is also observed at ambient conditions in nanometer-thin CsCl films grown on mica , LiF, KBr and NaCl substrates. Caesium chloride is colorless in the form of large crystals and white when powdered. It readily dissolves in water with the maximum solubility increasing from 1865 g/L at 20 °C to 2705 g/L at 100 °C. The crystals are very hygroscopic and gradually disintegrate at ambient conditions. Caesium chloride does not form hydrates . In contrast to sodium chloride and potassium chloride , caesium chloride readily dissolves in concentrated hydrochloric acid. Caesium chloride has also

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2808-623: Was first reported in 1905 by the French chemist M. L. Hackspill and is still used industrially. Caesium hydroxide is obtained by electrolysis of aqueous caesium chloride solution: Caesium chloride is widely used in centrifugation in a technique known as isopycnic centrifugation . Centripetal and diffusive forces establish a density gradient that allow separation of mixtures on the basis of their molecular density. This technique allows separation of DNA of different densities (e.g. DNA fragments with differing A-T or G-C content). This application requires

2862-466: Was studied using conventional non-radioactive CsCl. Whereas conventional caesium chloride has a rather low toxicity to humans and animals, the radioactive form easily contaminates the environment due to the high solubility of CsCl in water. Spread of CsCl powder from a 93-gram container in 1987 in Goiânia , Brazil, resulted in one of the worst-ever radiation spill accidents killing four and directly affecting 249 people. The caesium chloride structure adopts

2916-428: Was used in isolation of caesium, contained about 0.17 mg/L of CsCl. None of these minerals are commercially important. On industrial scale, CsCl is produced from the mineral pollucite , which is powdered and treated with hydrochloric acid at elevated temperature. The extract is treated with antimony chloride , iodine monochloride , or cerium(IV) chloride to give the poorly soluble double salt, e.g.: Treatment of

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