Cesium halides

Cesium Halides. Cesium bromide, [7787-69-1], CsBr, mol wt 212.82, theoretical cesium content 62.45%, is a colorless crystalline soUd, having a melting point of 636°C, a specific gravity of 4433 kg/m, and a solubUity of 1.23 kg/L of water at 25°C. It is usuaUy prepared by neutrali2ing the carbonate or hydroxide with HBr, but it is also the primary product of the Dow process (25) for poUucite processing. 

Taking the ionic radii for Cs+, Cl , Br , and I from Table 42, calculate in cubic centimeters per mole the volumes which the cesium halides would have if they crystallized in the sodium chloride structure, nnd compare with the values plotted in Fig. 57. 

Systematizing these results, we see that both in Fig. 72 and in Fig. 73, if we follow tho succession of curves from top to bottom, we go from ions of dissimilar character to ions of similar character in Fig. 73 we go down to Li+ and (Oil)", both strong order-producing ions, while in Fig. 72 we go down to Cs+ and Br", both strong order-destroying ions. If the same rule—from dissimilar character downward to similar character— is to be applied to the rubidium and cesium halides, the order I, Br, Cl, F, will clearly have to be reversed, in order that Rbl and Csl shall be the lowest in each case. It has been known for several years that such an inversion exists. Table 40, compiled by Robinson and Harned, shows the order observed in the whole set of iodides, bromides, and chlorides. It will be seen that, for RbCl, RbBr, and Rbl, and likewise for CsCl, CsBr, and Rbl, the observed order is opposite to that found for the other alkali halides. Hitherto this inversion has been regarded as mysterious. But it falls in line with the facts depicted in Fig. 72,... 

Dr. Hafemeister Perlow and Boyle at Argonne have studied Cs and the cesium halides. 

O Predict the periodic trend you would expect in the melting points of the following cesium halides CsF, CsCl, CsBr, Csl. Explain your... 

One of the most interesting aspects of molten salt chemistry is the readiness with which metals dissolve. FOr example, the alkali halides dissolve large amounts of the corresponding alkali metal, and some systems (e.g., cesium in cesium halides] are completely miscible at all temperatures above the melting point. On the other hand, the halides of zinc, lead, and tin dissolve such small amounts of the corresponding free metal that special analytical techniques must be devised in order to estimate the concentration accurately. 

Re(CO)4Cl(NS)][AsF6] CH3CN, is produced from trarax-[Re(CO)4(CH3CN)(NS) [AsF6]2 by its reaction with cesium halides. 

Ion-pair formation is more clearly seen in cesium halide solutions than in other alkali halide solutions discussed previously, because of weak hydration of cesium ions. The formation of contact ion pairs between Cs+ and F ions has been suggested by Szasz and Heinzinger (33) in 2.2 mol dm-3 aqueous solution. 

Since the sum of the ionic radii is known (from x-ray studies), both radii may then be evaluated. Similarly, if the S values for the argon, krypton, and xenon structures are known, the interionic distances in KC1, RbBr, and Csl may be used to calculate ionic radii for K+, Rb+, Cs4, Cl, Br, and I . The values for cesium and iodide ions must be regarded cautiously (for, as we shall see presently, the structure of the cesium halides is different from that of the other alkali halides) but the radii of the retnaining ions fit into a self-consistent system. Thus, adding from sodium fluoride (0.95 k) to R Br from rubidium bromide (1.95 A) yields a sum not greatly different from the observed interionic distance in solid sodium bromide (2.98 A). 

Their results are summarized in Table I. It can be seen that the degree of association is strongest for the lithium halides and diminishes monotonically toward the cesium halides. 

Our earliest alkali halide studies were performed with cesium halides, since the prevailing evidence (Table I) indicated that the vapor would be predominantly monomeric, and hence simplest to interpret. The apparatus employed for these studies (Figure 1) consisted of a cylindrical mirror electron energy analyzer, a non-inductively wound oven for generating the cesium halide vapor, and a helium resonance lamp. The spectra we obtained ( ) for the cesium halides are displayed in Figure 2. They reveal a clearly resolved doublet for Csl, a partially resolved doublet for CsBr, and broad single peaks for CsCl and CsF. We shall briefly reproduce here the arguments we used to interpret these spectra. 

Experimental values lithium halides from ref. 18(1979) sodium, potassium and rubidium halides from ref. 11 (1974) cesium halides from ref. 8 (1973). unresolved, only one peak observed, resolved into two, but not three components. 

When it was on, the equilibrium could be shifted strongly in favor of monomer. In contrast to our early work with the cesium halides, where we sought to minimize the dimer contribution in order to simplify the spectrum, we now wanted samples which would maximize the dimer concentration. From the data given in Table I, we knew these to be the lithium halides. 

We had previously used this technique for studying several alkali halides, including Nal, (23) the cesium halides (2A) and the rubidium halides. (25) The apparatus consisted of a one-meter normal incidence monochromator and a magnetic mass spectrometer. In these earlier studies, ionic species attributable to dimer and monomer were studied, but the intensity of trimer was too weak for measurement. With our more recent interest in trimer, we once again turned to the lithium halides. This time, our apparatus consisted of a three-meter normal incidence monochromator and a quadrupole mass spectrometer. (7 )... 

Vibrational constants are from Herzberg (2). Rotational constants were estimated using relationships in Herzberg (2). Bond length estimated by comparison of the mercurous halides with thallum and cesium halides. 

When the hard-sphere cation-anion radius ratio exceeds 0.732, as it does for the cesium halides, a different crystal structure called the cesium chloride structure, is more stable. It may be viewed as two interpenetrating simple cubic lattices, one of anions and the other of cations, as shown in Figure 21.17. When the cation-anion radius ratio is less than 0.414, the zinc blende, or sphalerite, structure (named after the structure of ZnS) results. This crystal consists of an fee lattice of... 

Halo-substituted thiatriazines 6 can be obtained from 1,2,4,6-thiatriazinium salts 5 with cesium halides or nitrosyl chloride. Potassium iodide gives the hypothetical 1-iodothiatriazine 6d which undergoes a homolytic decomposition into iodine and a 3,5-difluorothiatriazinyl radical 8. The structure of the soluble 1-iodothiatriazine 6e (R = Ph, X = I) was identified by an X-ray investigation.79... 

The decisive factor for a series of alkali halides with the same halogen is the decrease in lattice energy in passing from the lithium to the cesium halide. Account must also be taken of the reduction in the combination energy with increasing anion radius as halide ions are added to the alkyl-alane and with increasing length of the hydrocarbon chain of the trialkyl-alane (156, 294, 317). 

Silver(III) Compounds. No simple sfl.ver(III) compounds exist. When mixtures of potassium or cesium halides are heated with silver halides in a stream of fluorine gas, yellow KAgF4 [23739-18-6] or CsAgF4 [53585-89-0], respectively, are obtained. These compounds are diamagnetic and extremely sensitive to moisture (21). When Ag2S04 is treated with aqueous potassium persulfate in the presence of ethylenedibiguanidinium sulfate, the relatively stable Ag(III)-ethylenebiguanide complex is formed. 

Fatemi F K, Fatemi D J and Bloomfield L A 1996 Thermal isomerization in isolated cesium-halide clusters Phys. Rev. Lett. 77 4895... 

Later, Falkenhagen and co-workers and Onsager and Fuoss established a method of calculating parameter A starting from the Debye-Huckel theory. However, the above equation is only valid for concentrations up to about 0.01 mol/L. According to the above equation the relative viscosity should always increase with concentration. However, experiments show non-monotonic behavior for several electrolytes such as most of the potassium halides, and several mbidium and cesium halides [12]. 

CARBIDES OXIDES FLUORITES SULFIDES ALKALI HALIDES CESIUM HALIDES... 

Cesium halides differ from other alkali halides crystallographically. They are simple cubic while the other alkali halides have a face-centered cubic structure. Because of this, R ions occupy the interstitial sites in cesiiun halides instead of the substitutional sites in the other alkali halides. 

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