Caesium bromide iodide

We are now led to introduce a second empirical correction into our calculations. The theoretical values for the rubidium, caesium, bromide, and iodide ions in Table III resulted from the assumption that SE is independent of Z, which is known not to be true for these structures, on account of the difference between SE<1 and SEw. The solution values of R, which we may assume to hold also for gaseous ions in these cases, also show that the screening constant for the negative ions should be larger and for the positive ions smaller than that used that is, as Z increases SE decreases, presumably approaching our theoretical values for Z large. We shall assume that SE is a linear function of Z in this region, and evaluate the parameters of the function with the use of the solution values for the bromide and iodide ions. If we write... 

In contrast to the potassium and caesium halide melts, a monotonous change of the dissociation constant of carbonate ion in the sequence of sodium halides was observed. This distinction has been explained on p. 147 by the different stabilities of the inner complexes formed by melt ions in individual molten alkali metal halides, and by the different character of their changes with the change in the melt anion. The stability of the complex changes greatly in the potassium and caesium chloride-bromide-iodide sequences (the minimum is observed in the bromide melts), whereas in the sodium halides the chloride complexes possess the lowest stability and the iodide... 

The Group 1 halides have the NaCl structure (6 6 coordination) except for the chloride, bromide and iodide of caesium, which have the CsCl structure (8 8 coordination). The plots shown in Figure 3.3 show a general decrease in the negative value of as the cation radius... 

Uses Of the Stassfurt salts.—The magnesium compounds in the Stassfurt salts are used for the preparation of magnesium and of its salts. The potash salts are an essential constituent of many fertilizers used in agriculture, etc. 22 and potassium chloride is the starting-point for the manufacture of the many different kinds of potassium salts used in commerce—carbonate, hydroxide, nitrate, chlorate, chromate, alum, ferrocyanide, cyanide, iodide, bromide, etc. Chlorine and bromine are extracted by electrolysis and other processes from the mother liquids obtained in the purification of the potash salts. Boric acid and borax are prepared from boracite. Caesium and rubidium are recovered from the crude carnallite and sylvite. 

The reported specific gravity of ammonium iodide 3 ranges from H. G. F. Schroder s 2 443 to H. Schifi and U. Monsacchi s 2"5168 (15°). The best representative value may be taken as 2-511. The molecular volumes of the ammonium halides come between those of rubidium and caesium halides for example, ammonium chloride, 34-01 ammonium bromide, 39 62 ammonium iodide, 57 51. W. Biltz has also studied the mol. vol. of this salt. 

The Equation of State of the Alkali Halides.—The alkali halides, the fluorides, chlorides, bromides, and iodides of lithium, sodium, potassium, rubidium, and caesium have been more extensively studied experimentally than any other group of ionic crystals. For most of these materials, enough data are available to make a fairly satisfactory comparison between experiment and theory. The observations include the compressibility and its change with pressure, at room temperature, from which the quantities ai(T), o2(r) of Eq. (1.1), Chap. XIII, can be found... 

All the alkali metal halides except the cliloride, bromide and iodide of caesium form cubic crystals with the rock salt lattice and show a co-ordination number of 6. The exceptions are also cubic, but have the caesium chloride structure (Fig. 133) characterised by a co-ordination number of 8. The radius ratio for CsCl, Cs /Cl" = 0.93, allows 8 co-ordination, but is so near the ratio for 6 co-ordination that caesium chloride is dimorphous, changing, at 445°, from the caesium chloride to the rock salt structure. The crystalline halides are generally markedly ionic, though, as expected, lithium iodide is somewhat covalent, for iodide is the largest and most easily polarised simple anion and lithium, the smallest alkali metal cation, possesses the strongest polarising power. 

It is a remarkable feature that the experimental data obtained in Na+-based halides had led Smirnov to the conclusion that the minimum complexation ability takes place in chloride melts [81], but it is not so for potassium- and caesium-based halides. Therefore, the stability of alkali metal cation-halide ion is dependent not only on the anion properties but also on those of the cation. In the potassium and caesium halides this reason shifts the minimum of the complexation ability to the bromide melts, which makes these media more acidic than the corresponding chlorides and iodides. 

However, let us return to the solubility data in caesium iodide-melt at 700 °C. It can be seen that the oxide solubilities in this melt are intermediate between those in KCl-NaCl (CsCl-KCl-NaCl) and CsBr-KBr melts. Since for the said iodide-melt the range of oxides suitable for the investigations is too small, compared with other halides, and the range of solubilities is too narrow, some of the correlations considered above have not been analysed for molten Csl. Nevertheless, for chloride, bromide and iodide-melts, linear correlations between pPMe0 and rk 2 can be found, and the corresponding parameters of equation (3.7.16), with their confidence ranges, are presented in Table 3.7.16. 

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