It then sharply drops by two orders of magnitude because of the phase transition from the α-CsCl to β-CsCl phase. The conductivity increases with temperature up to about 450 ☌, with an activation energy changing from 0.6 to 1.3 eV at about 260 ☌. It occurs through nearest-neighbor jumps of lattice vacancies, and the mobility is much higher for the Cl − than Cs + vacancies. The conductivity has a value of the order 10 −7 S/cm at 300 ☌. ĭespite its wide band gap of about 8.35 eV at 80 K, caesium chloride weakly conducts electricity, and the conductivity is not electronic but ionic. Caesium chloride has also a relatively high solubility in formic acid (1077 g/L at 18 ☌) and hydrazine medium solubility in methanol (31.7 g/L at 25 ☌) and low solubility in ethanol (7.6 g/L at 25 ☌), sulfur dioxide (2.95 g/L at 25 ☌), ammonia (3.8 g/L at 0 ☌), acetone (0.004% at 18 ☌), acetonitrile (0.083 g/L at 18 ☌), ethylacetate and other complex ethers, butanone, acetophenone, pyridine and chlorobenzene. In contrast to sodium chloride and potassium chloride, caesium chloride readily dissolves in concentrated hydrochloric acid. The crystals are very hygroscopic and gradually disintegrate at ambient conditions. It readily dissolves in water with the maximum solubility increasing from 1865 g/L at 20 ☌ to 2705 g/L at 100 ☌. Physical properties Ĭaesium chloride is colorless in the form of large crystals and white when powdered. The rocksalt structure is also observed at ambient conditions in nanometer-thin CsCl films grown on mica, LiF, KBr and NaCl substrates. Upon heating to above 445 ☌, the normal caesium chloride structure (α-CsCl) converts to the β-CsCl form with the rocksalt structure ( space group Fm 3m). 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. In contrast, the other alkaline halides have the sodium chloride (rocksalt) structure. This structure is shared with CsBr and CsI and many binary metallic alloys. 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. The caesium chloride structure adopts a primitive cubic lattice with a two-atom basis, where both atoms have eightfold coordination. Spread of 137CsCl 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. 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. Another form of cancer treatment was studied using conventional non-radioactive CsCl. When enriched in radioisotopes, such as 137CsCl or 131CsCl, caesium chloride is used in nuclear medicine applications such as treatment of cancer and diagnosis of myocardial infarction. It is a reagent in analytical chemistry, where it is used to identify ions by the color and morphology of the precipitate. Ĭaesium chloride is widely used medicine structure in isopycnic centrifugation for separating various types of DNA. Less than 20 tonnes of CsCl is produced annually worldwide, mostly from a caesium-bearing mineral pollucite. Caesium chloride occurs naturally as impurities in carnallite (up to 0.002%), sylvite and kainite. CsCl changes to NaCl structure on heating. Its crystal structure forms a major structural type where each caesium ion is coordinated by 8 chloride ions. This colorless salt is an important source of caesium ions in a variety of niche applications. Caesium chloride or cesium chloride is the inorganic compound with the formula Cs Cl.
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