Pure alkali metal preparation is a complex problem: in most available commercial samples, all of them are simultaneously present. Conventional separation techniques are not always effective enough to reach parts per million total impurity levels. However, near the melting point, superficial segregation occurs. A zone melting derived technique coupled with a specifically developed solvent extraction process allows the total impurity content of sodium to be lowered below a few parts per million. The described thermal process, although using chemical reactions, is purely physically steered: it purifies as well potassium containing sodium as sodium containing potassium. 4 alkali metals are considered: Li, Na; K, and Cs.
Authors:N. Misra, K. Singh Mudher, and V. Venugopal
Preparation and characterization of four new hydrated alkali metal molybdates Na2Mo4O136H2O, K2Mo4O133H2O, Rb2Mo4O132H2O and Cs2Mo4O132H2O are described. The compounds were prepared by crystallizing the solution obtained by dissolving MoO3 and corresponding alkali metal carbonates A2CO3 or molybdate A2MoO4 in stoichiometric amount in distilled water. The hydrated molybdates were characterized by thermal (TG/DTA) and X-ray diffraction
(XRD) methods. The number of water molecules in the compounds were determined from their TG /DTA curves recorded in air and
identification of their dehydration products was done by XRD. The cell parameters of the compounds were obtained by indexing
their XRD patterns. Attempt to prepare the corresponding hydrated compound of lithium was not successful.
An approach allowing establishment of the relationship between the energies of mixing in binary homovalent melts of metals
and the corresponding values for halide salts (chlorides or fluorides) of these metals is proposed. The procedure given as
an example for estimation of the exchange energies in liquid-phase systems formed by lithium and other alkali metals allows
a considerable reduction in the number of experimentally complicated definitions for thermodynamic characteristics of similar
, the binding constants of di-ionizable p - tert -butylcalixarene conformers toward dissolved alkalimetal cations were determined. Nine scaffolds were used to assess the binding constants of isoconformations using ITC experiments
Authors:K. Muthu, G. Bhagavannarayana, S. P. Meenakashisundaram, and S. C. Mojumdar
The powder XRD patterns of Na(I)-doped samples are compared with that of undoped one ( Fig. 3 ). No new peaks or phases were observed by doping with alkalimetal sodium. However, a drastic reduction in intensity is observed as a result of doping. The
Authors:A. A. Opalovsky, V. E. Fedorov, and T. D. Fedotova
The thermal stability and non-isothermal kinetics of the decomposition of alkali metal bifluorides were studied using a derivatograph. The removal of hydrogen fluoride from LiF · HF and NaF · HF takes place before melting and their decomposition occurs in a single stage; however, potassium, rubidium and cesium bifluorides at first undergo polymorphous transformation and melting on heating, and their decomposition proceeds stepwise. The thermal stability of alkali metal bifluorides has been found to increase with increasing ionic radius of the cation, reflecting its correlation with the hydrogen bond strength in these compounds.
Authors:T. Meisel, Z. Halmos, K. Seybold, and E. Pungor
The thermal decompositions of lithium, sodium, potassium, rubidium and caesium formates were investigated by a complex dynamic thermoanalytical method. The ratio of the products in reactions resulting in alkali metal carbonates and oxalates depended variously on the atmosphere used. Differences were found compared to isothermal investigations, in that the catalytic effects of bases could not be observed and the oxalate-conversion was lower. The formation of oxalate did not occur in the cases of lithium and caesium formates; the order for the other salts was sodium formate < potassium formate > rubidium formate.
Authors:A. Hadj Mebarek, S. Walter, G. Killé, and C. Cogneville
Alkali metal alkoxides can be formed by the direct reaction of alkali metals with the corresponding alcohol. Under certain conditions, however, these reactions become dangerous. One of the reasons for the instability build-up in the reaction mixture is related to the electrochemical behaviour of the heterogeneous medium. Another reason is the instability introduced by the simultaneous presence of oxygen and alkali metal atoms in the reagents. Accelerating rate calorimetry is an excellent way to determine safe working conditions for the handling of such compounds. The hazards that are encountered are discussed by means of some examples.