High-voltage electroconduction in molten chlorides of alkaline-earth metals

Effects of high-voltage pulses on electroconduction of molten chlorides of alkaline-earth metals and their mixtures with potassium chloride are studied experimentally. It is established that the electroconductivity of the melts subjected to the pulses increases proportionally to the voltage amplitude and the number of activating pulses in a pulse series. Oscillatory relaxation of nonequilibrium melts is discovered.     

Cube-type nitrido complexes containing titanium and alkali/alkaline-earth metals

Treatment of [[Ti(eta(5)-C(5)Me(5))(mu-NH)](3)(mu(3)-N)] with alkali-metal bis(trimethylsilyl)amido derivatives [M[N(SiMe(3))(2)]] in toluene affords edge-linked double-cube nitrido complexes [M(mu(4)-N)(mu(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)]](2) (M = Li, Na, K, Rb, Cs) or corner-shared double-cube nitrido complexes [M(mu(3)-N)(mu(3)-NH)(5)[Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)](2)] (M = Na, K, Rb, Cs). Analogous reactions with 1/2 equiv of alkaline-earth bis(trimethylsilyl)amido derivatives [M[N(SiMe(3))(2)](2)(thf)(2)] give corner-shared double-cube nitrido complexes [M[(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)](2)] (M = Mg, Ca, Sr, Ba). If 1 equiv of the group 2 amido reagent is employed, single-cube-type derivatives [(thf)(x)[(Me(3)Si)(2)N]M[(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)]] (M = Mg, x = 0; M = Ca, Sr, Ba, x = 1) can be isolated or identified. The tetrahydrofuran molecules are easily displaced with 4-tert-butylpyridine in toluene, affording the analogous complexes [(tBupy)[(Me(3)Si)(2)N]M[(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)]] (M = Ca, Sr). The X-ray crystal structures of [M(mu(3)-N)(mu(3)-NH)(5)[Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)](2)] (M = K, Rb, Cs) and [M[(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3))-N)](2)] (M = Ca, Sr) have been determined. The properties and solid-state structures of the azaheterometallocubane complexes bearing alkali and alkaline-earth metals are discussed.     

Characterization and semiquantitative estimation of organophosphorus compounds based on inhibition of cholinesterases

A rapid and simple spectrophotometric method is presented for the characterization and semiquantitative determination of toxic organophosphorus compounds. The method relies on the inhibition of various cholinesterases and involves calculation of bimolecular rate constants for reactions of compounds with cholinesterase preparations from different animal tissues. In experiments with sarin, soman, tabun, diisopropyl fluorophosphate and 2,2′-dichlorovinyldimethyl phosphate, the mean relative standard deviation obtained for the rate constants was 9%. The detection limits for the compounds were at the picogram level. The amount of compound needed for characterization, which depends on both the set of enzymes and the compound itself, was at the pg- or ng-level. As a test of the method, a concentrate of urban air spiked with sarin was examined.     

Vapor pressure and activity of components of melts formed by manganese chloride and chlorides of alkaline-earth metals

The boiling points of melts were measured at different pressures over the melts for certain concentrations of components of the liquid phase in binary systems constituted by manganese chloride and chlorides of alkaline-earth metals. The temperature dependences of the saturated vapor pressure, normal boiling points, and enthalpies of evaporation were calculated. The concentration dependences of the thermodynamic activities of the components of four binary systems were analyzed.     

Use of polysulfides of alkali and alkaline-earth metals to obtain highly dispersed sulfur

Possibilities of obtaining polysulfides of alkali and alkaline-earth metals in aqueous solutions were considered. The composition of the polysulfides and their concentration in solutions were found. The efficiencies of application of highly dispersed sulfur, produced from calcium polysulfide, and colloid sulfur as a fungicide were compared.     

Molecular design of macrocyclic extractants for extraction and separation of alkali and alkaline-earth metals

The distribution coefficients of the alkaline and alkali-earth metal nitrates are determined for the processes of extraction from nitric acid solutions with crown ethers, which differ in sizes of their cycles (from 18 to 22 atoms) and in side phenyl and cyclohexyl substituents, but have unchanged number of the O atoms in a cycle. The phenyl and cyclohexyl derivatives of 18-crown-6 are found to be more efficient extractants of alkali metals as compared with unsubstituted crown ethers. However, the selectivity of separation of a pair Cs-Na remains low. The 18-crown-6 derivatives with one and two cyclohexyl fragments selectively extract Sr, which can be used to separate it from the remaining alkali and alkaline-earth metals. An increase in the size of a macrocycle from 18 to 20 and 22 atoms leads to a reduction in the extraction efficiency for all alkali and alkaline-earth metals, insignificantly improves separation of a pair Cs-Na, but noticeably deteriorates Sr-Na separation.     

Field-evaporation mass spectroscopy applied to crown ether complexes with alkali and alkaline-earth metals

Field evaporation from solution has been used to detect crown-ether 15K5 and 18K6 coordination compounds formed with Na⁺, K⁺, Cs⁺, Ba²⁺ and Ca²⁺ in aqueous solution, both hydrated and unhydrated; the Ca²⁺·18K6·(H₂O)_n (n=0, 1, 2,...) compounds have been observed before. 18K6 present in the solution greatly increases the yields of 18K6 compounds with the dissociation products from Ba(NO₃)₂. The detection limits for 15K5 and 18K6 combined with Na⁺, K⁺, and Cs⁺ are approximately the same at 10^–7 g.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 2, pp. 239–242, March–April 1988.     

Temperature dependence of electric conductivity of molten binary mixtures of alkali and rare-earth metals chlorides

The temperature dependences of the specific and molar electric conductances of CeCl₃-MCl and LnCl₃-KCl (M=Li, Na, K, and Cs; Ln=Er and Yb) molten binary mixtures of various compositions were studied. The size of the cations of alkali and rare-earth metals was demonstrated to affect the intensity of the interactions of the components of the systems. Deviations of the molar conductance isotherms from additivity and dependence of the isotherms on the ratio between the mixture components were explained by the formation of complexes in the melts.     

Study of diffusion of alkali metals and ammonium chlorides through nanofiltration membrane with selective layer

The diffusion of alkali metals and ammonium chlorides through an OPMN-KM3 composite nanofiltration membrane is studied as a function of the electrolyte concentration on both sides of the membrane. A model is proposed for calculating diffusion coefficients that takes into account changes in the electrolyte concentration in selective pores of membrane. The diffusion coefficients are calculated both using the proposed model and by Fick’s equation. The effect of the orientation of the membrane with respect to the diffusion flux on the diffusion coefficients of salts is analyzed.     

Transformation of alkali and alkaline-earth metals during coal oxy-fuel combustion in the presence of SO_2 and H_2O

The occurrence modes of alkali and alkaline-earth metals(AAEMs) in coal relate to their release behavior and ash formation during combustion. To better understand the transformation of AAEMs,the release behavior of water-soluble,HCl-soluble,HCl-insoluble AAEMs during Shenmu coal(SM coal) oxy-fuel combustion in the presence of SO2 and H2O in a drop-tube reactor was investigated through serial dissolution using H2O and HCl solutions. The results show that the release rates of AAEMs increase with an increase in temperature under the three atmospheres studied. The high release rates of Mg and Ca from SM coal are dependent on the high content of soluble Mg and Ca in SM coal. SO2 inhibits the release rates of AAEMs,while H2O promotes them. The effects of SO2 and H2O on the Na and K species are more evident than those on Mg and Ca species. All three types of AAEMs in coal can volatilize in the gas phase during coal combustion. The W-type AAEMs release excessively,whereas the release rates of I-type AAEMs are relatively lower. Different types of AAEM may interconvert through different pathways under certain conditions. Both SO2 and H2O promote the transformation reactions. The effect of SO2 was related to sulfate formation and the promotion by H2O occurs because of a decrease in the melting point of the solid as well as the reaction of H2O.     

A photoelectron study of the alkali chlorides

Precise values have been determined for the binding energies of the outer electronic bands of the alkali chlorides using ultraviolet photoelectron spectroscopy. A constant difference of 1.2(1) eV between experimental and Born model binding energies is attributed to polarization effects. A splitting of 1.8 eV (spin-orbit) in the Cs 5p band, and a splitting of 2.1 eV (crystal field) in the LiCl (cl^?3p) band have been observed. The measured widths of the Cl^?3p bands are compared with density of states calculations.     

Uptake of radiocesium and alkali metals by mushrooms

Various mushrooms and soils were analyzed for alkali metals and for radiocesium. The obtained concentration factors of the nonradioactive Cs for mushrooms are not significantly different from that for vascular plants, whereas in the case of radiocesium the values found were orders of magnitude higher. The different behaviour of natural and radioactive cesium may be due to their disequilibrium in the ecosystems. The irradiation of man due to ingestion of contaminated mushrooms cannot cause a significant health risk.