Phase potassium/caesium

The potassium/caesium phase diagram is an example of a system involving the formation of mixed crystals with a temperature minimum (Fig. 4.4). The right and left halves of the diagram are of the same type as the diagram for antimony/bismuth. The minimum corresponds to a special point for which the compositions of the solid and the liquid are the same. Other systems can have the special point at a temperature maximum. 

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 sulphates of potassium, rubidium and caesium are isomorphous and anhydrous. The solubility of sodium sulphate depends upon the composition of the solid phase. It increases rapidly with temperature up to 32.38 , and within this range crystallisation gives the decahydrate. Above 32.38 the solubility falls slightly with temperature and the anhydrous salt separates as fine crystals. Lithium sulphate crystallises as the monohydrate, LigSO. HgO... 

The unsubstituted para-t-butyl calixarenes themselves complex metals via their aryloxide groups. Since aryloxide complexes are frequently oligomeric, the simple calixarenes do not give monomeric complexes. Aryloxides are hard ligands, therefore they readily form complexes with oxo-philic hard metal ions such as alkali metals, early transition metals, lanthanides, and actinides. Complexation is often inferred because the calixarene acts as a carrier for the metal ion from an aqueous to an organic phase. With the /wa-/-butylcalix[ ]arenes in alkaline solution, a value of n = 6 gives the best carrier for lithium(I), sodium(I), and potassium(I), with a value of n 8 giving the best carrier for rubidium(I) and caesium(I).15,16 Titanium(IV) complexes have been characterized,17-19 as well as those of niobium(V) and tantalum(V).20-22 These complexes are classified as... 

Limits of miscibility have been determined between lithium and potassium from 63 to 500 °C. Generally, lithium is less miscible with potassium than with sodium the tendency to separate into two immiscible liquids with lithium increases from sodium to caesium. In Li-K, between 63 and 180 °C, a K-rich liquid phase is in equilibrium with solid lithium, while two immiscible liquid phases are present above 180 °C. The solubilities S/(p.p.m. by weight) of K in liquid Li, and of Li in liquid K, determined by chemical analysis of the immiscible phases, are given, respectively, by 38... 

Fluorides of potassium, rubidium and caesium form compounds of composition Me3LnX6, which are stable in the solid and liquid state. In the phase diagrams mentioned there are some other compounds which, however, are unstable and decompose in the solid state during temperature elevation (excluding LaF3, where the adducts of MeLaF4 are stable enough). 

The caesium derivative was isomorphous to a potassium derivative. Data were collected on the potassium derivative on a conventional source at CuKa wavelength. Data were also collected at 2.47 A at the peak of the absorption of the caesium Lm edge where/" is a maximum. Data extended to a resolution of 3.8 A. The isomorphous and anomalous differences gave phases, which allowed an electron density map to be calculated the sense of progression of an a-helix was clearly recognisable from the map. 

The trimethylsilylated silicic acids formed in this instance are soluble in conventional organic solvents, and their volatility is sufficiently high for them to be analysed by gas chromatography. Carzo and Hoebbel [411] carried out a comprehensive study of the chromatographic retention of various trimethylsilylated silicic acids on different stationary phases Apiezon L and silicone OV-1 and OV-17. The analysis of metals in the form of volatile complexes continues to attract attention, and have been described for analysing sodium [412], potassium [412], radium [413], caesium [413], barium [414], calcium [414], strontium [415], beryllium [416, 417], magnesium [418], zinc [419, 420], nickel [419], mercury [421], copper [422, 423], silver [424, 425], cadmium [421], indium [426, 427], g ium [428], scandium [217], cobalt [421], thallium [426], hafnium [429, 430], lead [431, 432], titanium [430], vanadium [433], chromium [434-436], manganese [426], iron [437], yttrium [438], platinum [439,440], palladium [439, 441, 442], zirconium [430], molybdenum [443], ruthenium [444], rhodium [445], rare earths [446—449], thorium [221, 450, 451] and uranium [221, 452]. The literature on GC analysis of metal chelates was reviewed by Sokolov [458]. 

Andrews and co-workers have used the matrix reaction between lithium atoms and some inorganic compounds to produce species of spectroscopic interest. Reaction of lithium with molecular oxygen [301] produces, in addition to the molecule Li02, the molecule LiO and a dimer Li2 02. Reaction with nitric oxide produced a nitroxide compound [302], but analysis of the infrared spectrum indicated that in this compound the lithium atom was bound to the oxygen atom (LiON), rather than to the nitrogen atom (LiNO), as would be expected by analogy with the known compounds HNO and RNO. The matrix deposition of lithium and nitrous oxide [303] leads to the formation of LiO and LijO. The other alkali metals have also been reacted in the same way with nitrous oxide [304]. Potassium, rubidium and caesium all led to the formation of the compounds MO and M2O. No sodium oxides were produced when sodium and nitrous oxide were co-deposited. This is to be compared with the mechanism advanced for the sodium-catalysed gas-phase reaction between N2O and CO, where sodium is assumed to react with N2O, (Section 4, ref. 

Preparation.— Two procedures for the production of ethers from alky] halides have been mentioned earlier in this Report. From a study of fluoride salts on alumina as reagents for the alkylation of phenols and alcohols, potassium or caesium fluoride on alumina, in acetonitrile or 1,2-dimethoxyethane as the solvent, has been found to be the best combination for general use. A recently reported one-pot synthesis of phenyl ethers from phenol acetates involves their treatment, in solution in acetone, first with potassium carbonate and then with an alkyl halide. Another interesting new procedure for the alkylation of phenols utilizes the gas-liquid phase-transfer catalysis technique that was discussed above. In this case a phenol (or a thiophenol) and an alkyl halide, both gaseous, are passed through a bed of solid K2CO3 (or NaHCOs) at 170°C in the presence of a PEG e,g. Carbowax 6000) as the catalyst. ... 

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