Potassium rubidium and

Ammonium may be determined by predpitation with sodium tetraphenylborate as the sparingly soluble ammonium tetraphenylborate NH4[B(C6H5)4], using a similar procedure to that described for potassium it is dried at 100°C, For further details of the reagent, including interferences, notably potassium, rubidium, and caesium, see Section 11.38,... 

Whereas technique (4) works for all alkali metals, lithium and sodium behave differently from potassium, rubidium, and cesium with respect to graphite on direct combination. The last three react facilely with graphite, to form compounds CgM (first stage) and Ci2 M (stage n > 1), but lithium reacts only under more extreme conditions of temperature or pressure, or both, to form compounds of formula CenLi (G3,... 

X-ray crystallography of potassium, rubidium, and cesium methyls shows completely ionic crystal lattices Weiss, E. Sauermann, G. Chem. Ben, 1970, 103, 265 Weiss, E. Koster, H. Chem. Ber., 1977, 110, 717. 

Mercury forms amalgams with numerous metals. Usually, this conversion is very exothermic, therefore it can present risks the reaction can become violent if a metai is added too quickly into mercury. Accidents have been described with caicium (at 390°C), aluminium, alkali metals (lithium, sodium, potassium, rubidium) and cerium. Some of these alloys are very inflammable, in particular the Hg-Zn amalgam. 

Sodium silicide ignites in air [1], and like its potassium, rubidium and caesium analogues, ignites explosively on contact with water or dilute acids [2],... 

Monorubium acetylide and monocaesium acetylide incandesce with warm phosphorus. Lithium acetylide and sodium acetylide bum vigorously in phosphorus vapour, and the potassium, rubidium and caesium analogues should react with increasing violence. 

The 02 ion is known as the superoxide ion, and it is produced when oxygen reacts with potassium, rubidium, and cesium. 

Helmke PA, Sparks DL. Lithium, sodium, potassium, rubidium, and cesium. In Bartels JM (ed.), Methods of Soil Analysis Part 3 Chemical Methods. Madison, WI ... 

Fig. 1. Mean reduced vapor pressure curve for the halides of sodium, potassium, rubidium, and cesium. Average deviation from the mean is shown by the vertical lines.

Alkali metals, especially potassium, rubidium, and cesium Metal amides (e.g., NaNH2)... 

Metals react with nonmetals. These reactions are oxidation-reduction reactions. (See Chapters 4 and 18). Oxidation of the metal occurs in conjunction with reduction of the nonmetal. In most cases, only simple compounds will form. For example, oxygen, 02, reacts with nearly all metals to form oxides (compounds containing O2-). Exceptions are the reaction with sodium where sodium peroxide, Na202, forms and the reaction with potassium, rubidium, and cesium where the superoxides, K02, Rb02, and Cs02 form. 

FABMS has been used as a semiquantitative indication of the selectivity of receptors for particular guest metal cations (Johnstone and Rose, 1983). The FABMS competition experiment on [7] with equimolar amounts of the nitrates of sodium, potassium, rubidium and caesium gave gas-phase complex ions of ([7] + K)+ ion (m/z 809) and a minor peak ([7] + Rb)+ ion (m/z 855) exclusively. The relative peak intensities therefore suggested a selectivity order of K+ Rb+ Na+, Cs+, indicative of the bis-crown effect, the ability of bis-crown ether ligands to complex a metal cation of size larger than the cavity of a single crown ether unit, forming a sandwich structure. 

The metal fulminates are all powerfully explosive. Of several salts examined, those of cadmium, copper and silver were more powerful detonators than mercury fulminate, while thallium fulminate was much more sensitive to heating and impact. Formally related salts are also explosive [1]. Sodium, potassium, rubidium and caesium fulminates are all easily detonated by feeble friction or heat. They all form double salts with mercury(II) fulminate which also explode readily, that of the rubidium salt at 45 °C [2],... 

Potassium, rubidium and caesium tetrafluorochlorates and hexafluorobromates react violently with water, and explosively with common organic solvents, like the parent halogen fluorides [1], Silver and barium tetrafluorobromates ignite in contact with ether, acetone, dioxane and petrol [2], Individual entries are ... 

Stereospecific ketone reduction was also observed (Giordano et al. 1985) with potassium, rubidium, and cesium (but not with sodium) in tertiary alcohols (but not in secondary or primary alcohols). The undesirable dimerization probably proceeds more readily in the case of sodium. Tertiary alcohols are simply more acidic than primary or secondary alcohols. It is reasonable to point out that the ketone-to-alcohol reduction of 3a-hydroxy-7-oxo-5p-cholic acid by alkali metals is a key step in the industrial synthesis of 3a,7p-dihydroxy-5p-cholic acid. 

Heats of solution, hydration energies and lattice energies are discussed in reference (77). For oxygen and nitrogen donor atoms, only a few compounds of potassium, rubidium, and caesium are known, but several have been characterised for the smaller cations, sodium and lithium. 

The mixed alum solution, on treatment with ammonia or potassium carbonate, forms carbonates of potassium, rubidium and cesium. Rubidium carbonate is separated from other alkab metal carbonates by fractional crystal-bzation (see Rubidium)... 

Cheary, R. W. 1987. A structural analysis of potassium, rubidium and caesium substitution in barium hollandite. Acta Crystallographica, B43, 28-34. 

Fig. 32.—Solubilities of Potassium, Rubidium, and Caesium Perchlorates in Water.

Precipitate with aq. ammonia. Evaporate the soln. down to about 100 c.c., and filter the ot liquid so as to remove calcium sulphate. The cone. soln. is sat. with ammonium alum and allowed to stand for some time. The mixed crystals of potassium, rubidium, and oeesium alums and of lithium salt are dissolved in 100 c.c. of distilled water and recrystal-lized. The recrystallization is repeated until the crystals show no spectroscopic reaction for potassium or lithium. The yield naturally depends on the variety of lepidolite employed. 100. grms of an average sample gives about 10 grms. of crude crystals and about 3 grms. of the purified caesium and rubidium alums. For the purification of caesium and rubidium salts, see the chlorides. The mother-liquors are treated with an excess of barium carbonate, boiled, and filtered. The filtrate is acidified with hydrochloric acid, and evaporated to dryness. The residue is extracted with absolute alcohol in which lithium chloride is soluble, and the other alkali chlorides are sparingly soluble. 

The properties of the alkali metals and of their salts are roughly functions of the at. wt. of the metals. There is generally a break in the curve about potassium so that lithium and sodium form one series, and potassium, rubidium, and caesium another. The properties of the series, K, Rb, Cs generally change more regularly than the series Li, Na, K, although some irregularities do occur—e.g. the m.p. of the nitrates. 

The electro-affinity of lithium is smaller than that of any of the other alkali metals, and it exhibits a greater tendency than the other alkali metals to form complex salts—e.g. the solubility of ammonia in water is raised by the addition of a lithium salt, which presumably unites with the ammonia the solubility curves of the lithium salts in water usually show more breaks than the corresponding salts of the other alkali metals owing to the formation of hydrates. Potassium, rubidium, and caesium seem to have a smaller and smaller tendency to form complex salts as the at. wt. of the element increases otherwise expressed, the electro-affinity, or the ionization tendency of the alkali metals increases as the at. wt. increases. This is illustrated by the heats of ionization. According to W. Ostwald,27 the heat of ionization per gram-atom iB... 

---