Cesium-chloride compounds

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.

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. 

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 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. 

Fig. 4.1 Crystal structures of two 1 1 ionic compounds (a) unit cell of sodium chloride, cubic, space group Fm3m (b) unit cell of cesium chloride, cubic, space group Fm3m. [From Ladd, M.F C Structure and Bonding in Solid State Chemistry, Wiley New York, 1979. Reproduced with permission.]...

Each compound was soaked for 1 hr in 38% (wt/v) HC1 followed by soaking in 55% (wt/v) HF for 1 hr. Each was then rinsed exhaustively with water and dried under vacuum at room temperature. In a separate experiment each of the model compounds were exposed to a solution of cesium chloride. After sufficient exposure each compound was recovered and washed with copious quantities of distilled water. The percentage recovery, the melting point and spectroscopic data such as FTIR, proton and carbon-13 NMR were recorded. 

Ammonophosphorous acids, nomenclature of, 2 265 Anatase, formation of, by 7-ti-tanium(IV) oxide, 6 82 Aniline, compound with thorium acetylacetonate, 2 215 5-Anilino-l,2,3,4-thiatriazole, 6 45 Anions, nomenclature of, 2 258 Antimony(III) cesium chloride, 2SbCl3-3CsCl, precipitation in extraction of cesium from pollu-cite, 4 6... 

Cesium iododichloride crystallizes in beautiful orange rhombohedral needles or plates. The compound is stable indefinitely in closed containers but slowly whitens when exposed to air, reverting to cesium chloride. The cesium trihalides are more stable thermally and less soluble than those of the other alkali metals. 

For those ionic compounds (such as cesium chloride) in which the radius ratio rc/r exceeds 0.73 it is possible to group eight anions tightly around each cation. The anions may be considered to occupy the comers of a cube with the cation in the center, or alternately, an anion may be regarded as the center of a cube with eight cations grouped around it the... 

The three structures already described (the zinc blende, sodium chloride, and cesium chloride arrangements) must of necessity be confined to compounds of simplest formula AiCv The two most important type structures for compounds of type, AC2 (or A2C), are the fluorite (CaF2) and rutile (Ti02) structures. 

The pink crystals can now be collected by filtration in air. They are washed twice with 10-ml. portions of absolute ethanol, and placed in a desiccator over KOH pellets for 10 hours. Yield is 1.95 g. (ca. 70%). Anal. Calcd. for [NH4]8[MoC16] N, 11.58 Mo, 26.44. Found N, 11.5 Mo, 26.7. The same procedure may be followed for the rubidium and cesium compounds, using 1.0 g. rubidium chloride or 1.5 g. cesium chloride in place of 0.5 g. ammonium chloride (see Note page 173). 

If the substance is a binary compound AB, and if its unit cell is simple cubic P with one formula (one atom of A and one of B) per cubic cell, the relative positions of the two atoms are fixed by symmetry. This is tme of the salt cesium chloride, CsCl, the structure of which is shown in Fig. 4. One of the ions, Cs say, may without loss of generality be placed at the origin. The other ion, Cr, must be at the center of the unit cell if it is in any other position, the stracture will lack the threefold rotational axes of synunetry that are always present along all four body diagonals of the unit cell in the cubic system. 

Several crystalline ternary intermetallic compounds ate presently used in engineering applications. The ternary phase Ni2Mnln (Pearson symbol cF16) is illustrated in Figure 3.26a. Each atom is located on the site of a cesium-chloride cubic lattice. The unit cell consists of a FCC arrangement of nickel atoms with one additional nickel... 

If half of the nickel atoms in Figure 3.26a are removed, the half-Heusler ABC structure of Figure 3.26b is obtained. In the half-Heusler strucmre, each atom still resides on a cesium-chloride lattice site. The rock-salt component (B and C) remains intact, but the A atoms form a zinc blende lattice with B and C. Examples of compounds with this structure include MnNiSb, AuMgSn, BiMgNi, and RhSnTi. 

The structure of sodium chloride, which is the prototype for most of the alkali halides, is best described as a cubic closest packed array of Cl- ions with the Na+ ions in all of the octahedral holes [see Fig. 16.42(b)]. The relative sizes of these ions are such that rua 0.66i ci-> so this solid obeys the guidelines given previously. Note that the CP ions are forced apart by the Na+ ions, which are too large for the octahedral holes in the closest packed array of CP ions. Since the number of octahedral holes is the same as the number of packed spheres, all the octahedral holes must be filled with Na+ ions to achieve the required 1 1 stoichiometry. Most other alkali halides also have the sodium chloride structure. In fact, all the halides of lithium, sodium, potassium, and rubidium have this structure. Cesium fluoride has the sodium chloride structure but because of the large size of Cs+ ions, in this case the Cs ions form a cubic closest packed arrangement with the F ions in all the octahedral holes. On the other hand, cesium chloride, in which the Cs+ and CP ions are almost the same size, has a simple cubic structure of CP ions, with each Cs+ ion in the cubic hole in the center of each cube. The compounds cesium bromide and cesium iodide also have this latter structure. 

The HjC-O-Te bonds are remarkably stable no cis-trans isomerization was observed when the hydroxy methoxy tellurium tetrafluorides were kept at temperatures below 130°. The bonds are not cleaved by 65% oleum or chlorosulfonic acid at room temperature, instead, the sulfate esters HjCO-TeF tO-SOjH) were formed. These sulfate esters were transformed to HO-TeFiCO-SOjH) upon heating to 100°. Cesium chloride dissolved in an excess of cis- or /run.s-hydroxy methoxy tellurium tetrafluoride liberated hydrogen chloride with the formation of very hygroscopic cesium methoxo(oxo)letrafluorotellurates(VI). Trunj-hydroxy methoxy tellurium tetrafluoride reacts instantaneously with water with loss of fluoride. The cu-compound is stable toward hydrolysis at room temperature. ... 

Cesium compounds have relatively few commercial uses. Cesium bromide is used to make radiation detectors and other measuring devices. Cesium carbonate and cesium fluoride are used to make specialty glasses. Cesium carbonate and cesium chloride are used in the brewing of beers. Cesium compounds are also used in chemical research. 

Figure 13-29 Crystal stmctures of some ionic compounds of the MX type. The gray circles represent cations. One unit cell of each stmcture is shown, (a) The stmcmre of cesium chloride, CsCl, is simple cubic. It is not body-centered, because the point at the center of the cell (Cs+, gray) is not the same as the point at a corner of the cell (Cl , green), (b) Sodium chloride, NaCl, is face-centered cubic, (c) Zincblende, ZnS, is face-centered cubic, with four Zn + (gray) and four (yellow) ions per unit cell. The...

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