Cesium chloride

Data reported for the protolysis constant of water in cesium chloride media are listed in Table 5.8. The data are solely for a temperature of 25 °C, with the majority of data reported by Lucas (1967) and a single datum reported by Sipos et al. (2006). 

Use of Eq. (5.17) requires data for the activity of water in cesium chloride media. Water activity data can also be determined from osmotic coefficient data through use of Eq. (5.18)  

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Table 2 Hsts examples of compounds with taste and their associated sensory quaUties. Sour taste is primarily produced by the presence of hydrogen ion slightly modified by the types of anions present in the solution, eg, acetic acid is more sour than citric acid at the same pH or molar concentration (43). Saltiness is due to the salts of alkaU metals, the most common of which is sodium chloride. However, salts such as cesium chloride and potassium iodide are bitter potassium bromide has a mixed taste, ie, salty and bitter (44). Thus saltiness, like sourness, is modified by the presence of different anions but is a direct result of a small number of cations.

Decomposition with Bases. Alkaline decomposition of poUucite can be carried out by roasting poUucite with either a calcium carbonate—calcium chloride mix at 800—900°C or a sodium carbonate—sodium chloride mix at 600—800°C foUowed by a water leach of the roasted mass, to give an impure cesium chloride solution that is separated from the gangue by filtration (22). The solution can then be converted to cesium alum [7784-17-OJ, CS2SO4 Al2(S0 2 24H20. Extraction of cesium from the poUucite is almost complete. Solvent extraction of cesium carbonate from the cesium chloride solution using a phenol in kerosene has also been developed (23). 

Hydrochloric acid digestion takes place at elevated temperatures and produces a solution of the mixed chlorides of cesium, aluminum, and other alkah metals separated from the sUiceous residue by filtration. The impure cesium chloride can be purified as cesium chloride double salts such as cesium antimony chloride [14590-08-0] 4CsCl SbCl, cesium iodine chloride [15605 2-2], CS2CI2I, or cesium hexachlorocerate [19153 4-7] Cs2[CeClg] (26). Such salts are recrystaUized and the purified double salts decomposed to cesium chloride by hydrolysis, or precipitated with hydrogen sulfide. Alternatively, solvent extraction of cesium chloride direct from the hydrochloric acid leach Hquor can be used. 

The residue is leached to give cesium sulfate solution, which can be converted to cesium chloride by ion exchange on Dowex 50 resin and elution with 10% HCl, treatment using ammonia or lime, to precipitate the alurninum, or by solvent extraction, followed by purification at neutral pH using hydrogen peroxide or ammonia. 

Most current appUcations require relatively smaU quantities of cesium, and hence aimual world production of cesium metal and compounds is estimated to be on the order of 250 t of cesium chloride equivalents. 

The cesium ion is more toxic than the sodium ion but less toxic than the potassium, lithium, or mbidium ion. No TLV is stated for cesium or cesium chloride the TLV for cesium hydroxide is 2 mg/m. The oral LD q of cesium chloride for mice is 2300 mg/kg, and for cesium fluoride is 400—700 mg/kg (39). 

Toyopearl HW-75 resin, with pores larger than 1000 A, have been used in place of ultracentrifugation steps for the purification of plasmid DNA. Ultracentrifugation is a time-consuming process and requires expensive chemicals, such as cesium chloride. Toyopearl HW-75 resin provides superior separation performance for plasmid DNA and also provides high yields (54). 

Purification of Pholas luciferase (Michelson, 1978). Acetone powder of the light organs is extracted with 10 mM Tris-HCl buffer, pH 7.5, and the luciferase extracted is chromatographed on a column of DEAE Sephadex A-50 (elution by NaCl gradient from 0.1 M to 0.6 M). Two peaks of proteins are eluted, first luciferase, followed by a stable complex of luciferase and inactivated pholasin. The fractions of each peak are combined, and centrifuged in 40% cesium chloride... 

FIGURE 5.41 The cesium chloride structure (a) the unit cell and (b) the location of the centers of the ions. 

FIGURE 5.42 The repetition of the cesium chloride unit cell recreates the entire crystal. This view is from one side of the crystal and shows several unit cells stacked together. 

Calculate the number of cations, anions, and formula units per unit cell in each of the following solids (a) the cesium chloride unit cell shown in Fig. 5.41 (b) the rutile (Ti02) unit... 

Estimate the density of each of the following solids from the atomic radii of the ions given in Fig. 1.48 (a) calcium oxide (rock-salt structure, Fig. 5.39) (b) cesium bromide (cesium chloride structure, Fig. 5.41). 

Are the following statements true or false (a) Because cesium chloride has chloride ions at the corners of the unit cell and a cesium ion at the center of the unit cell, it is classified as having a body-centered unit cell, (b) The density of the unit cell must be the same as the density of the bulk material, (c) When x-rays are passed through a single crystal of a compound, the x-ray beam will be diffracted because it interacts with the electrons in the atoms of the crystal, (d) All the angles of a unit cell must be equal to 90°. 

The density of cesium chloride is 3.988 g-em .Calculate the percentage of empty space in a cesium chloride lattice with the ions treated as hard spheres. 

Huggins, who has particularly emphasized the fact that different atomic radii are required for different crystals, has recently [Phys. Rev., 28, 1086 (1926)] suggested a set of atomic radii based upon his ideas of the location of electrons in crystals. These radii are essentially for use with crystals in which the atoms are bonded by the sharing of electron pairs, such as diamond, sphalerite, etc. but he also attempts to include the undoubtedly ionic fluorite and cesium chloride structures in this category. 

The alkali halides with the cesium chloride structure also show satisfactory agreement, the observed values being about 2.5% larger than the sum of the theoretical radii. 

Inter-Atomic Distances for Cesium Chloride Type Crystals... 

The Sodium Chloride and Cesium Chloride Structures.—The agreement found between the observed inter-atomic distances and our calculated ionic radii makes it probable that the crystals considered are built of only slightly deformed ions it should, then, be possible, with the aid of this conception, to explain the stability of one structure, that of sodium chloride, in the case of most compounds, and of the other, that of cesium chloride, in a few cases, namely, the cesium and thallous halides. 

These considerations also explain the occurrence of cases of dimorphism involving the sodium chloride and cesium chloride structures. It would be expected that increase in thermal agitation of the ions would smooth out the repulsive forces, that is, would decrease the value of the exponent n. Hence the cesium chloride structure would be expected to be stable in the low temperature region, and the sodium chloride structure in the high-temperature region. This result may be tested by comparison with the data for the ammonium halides, if we assume the ammonium ion to approximate closely to spherical symmetry. The low-temperature form of all three salts, ammonium chloride, bromide and iodide, has the cesium chloride structure, and the high-temperature form the sodium chloride structure. Cesium chloride and bromide are also dimorphous, changing into another form (presumably with the sociium chloride structure) at temperatures of about 500°. 

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