Alkali Compounds Research Articles

Ternäre zintl-Verbindungen mit thallium als elektronendonator

Two new ternary Zintl compounds, containing thallium as electropositive element 1. (A), a IIB-element 2. (B) and a pnictide (X), TlZn 2Sb 2 and Tl 2Cd 3Sb 3, have been prepared from mixtures of the elements at temperatures about 1000 K and studied by X-ray diffraction analysis. TlZn 2Sb 2 crystallizes with a tetragonal structure (space group I4, Z = 4) with a = 864.9(5) pm and c = 728.7(4) pm; Tl 2Cd 3Sb 3 is monoclinic (space group C2/ m, Z= 4) with a = 1732.8(8) pm, b = 486.8(3) pm, c = 1679.3(7) pm and β = 139.4(5)°. The crystal structures were refined from single-crystal diffractometer data. They show the same principles of atomic arrangement as those of TlCdSb and the corresponding sodium compounds. Thus, in difference to TlCdSb, TlZn 2Sb 2 and Tl 2Cd 3Sb 3 are not structurally isomorphous with known alkali compounds. The structures consist of three dimensional nets of tetrahedrally coordinated B- and X-atoms. The thallium atoms are arranged in linear (TlZn 2Sb 2) or zigzag chains (TlCdSb, Tl 2Cd 3Sb 3). These chains are enclosed by tunnels, built up from eight rings of (BX) 4 units, which are interlinked by B-X-bonds. As in some compounds of heavier alkali metals the distances inside the anionic substructure differ markedly from those between A-atoms and the atoms building the substructure. The special structural and binding properties are discussed.

First tandem mass spectrometric measurement of tropospheric ions

Tandem mass spectrometric measurements of naturally occurring tropospheric ions have identified pyridine, methylpyridine, and ethylpyridine as the parent neutral species responsible for ions observed at mass 80, 94, and 108, respectively. High‐resolution mass spectra of natural ions observed over an extended mass range are also shown for two field study locations. At one site (Sapelo Island, Georgia), pyridine and its homologues dominated the positive spectrum. At Mount Evans, Colorado, the second site, pyridine along with a large number of more massive and presumably very alkali species were observed to dominate the positive spectrum. In addition, X ray‐produced ion spectra were also measured and used to make rough estimates of the pyridine concentrations at the Sapelo site (∼10 ppt) and the total concentration of alkali compounds, excluding NH3, at Mount Evans (∼0.5 ppb).

Monitoring the condition of the slag crust in blast furnaces

Studies conducted at the Krivorozhstal' combine blast furnaces have shown that fusion of the crust can be established from the change in the total content of alkali metals in the slag. After the furnaces were blown out for repairs the remaining lining and crust were inspected. It was found that the lining of the uncooled part of the stock remained in relatively good shape with the greatest amount of lining wear seen between the second row of stack coolers and bosh coolers. The composition and structure of the slag crust for different regions of the furnaces were analyzed and various physicochemical properties leading to crust formation and behavior were assessed. It was concluded that the systematic determination of the fraction of K/sub 2/O in the alkali compounds in the furnace slag will permit monitoring of the conditions of the slag crust in the furnace and, in the event of the onset of its collapse, will enable measures to be taken to stabilize the heating of the furnace.

Darstellung neuer polycyclischer Methylsilane

Cyclosilyl alkali compounds are universal reagents for the preparation of polycyclic silanes. Undecamethylcyclohexasilanyl potassium reacts with different chlorosilanes yielding three new methylated polycyclic silanes, which have been isolated and characterized.

Studies of alkali-silica reaction. Part 4. Effect of different alkali salt solutions on expansion

It has been shown that the extent of expansion due to alkali-silica reaction depends on the type of alkali compound and its concentration in the sorrounding liquid phase. It is of particular interest to note that a 3N alkali hydroxide solution causes less expansion than a 3N alkali salt solution. The result also showed that the expansion due to alkali-silica reaction is not directly proportional to the degree of chemical reaction. These results, though at variance to a generally held belief, are consistent with a recently proposed mechanism of alkali-silica reaction. The results indicate that in an accelerated alkali-silica test the use of an alkali salt is preferable to an alkali hydroxide.

Thermal behaviour in air of a bituminous coal with high mineral matter content doped with compounds of alkali and alkaline earth metals

A study has been made of the catalytic behaviour of a number of compounds of alkali and alkaline earth metals on the gasification in air, in dynamic conditions, of chars from a bituminous coal with high mineral matter content provided in the mine of Bélmez (Córdoba, Spain). Some catalysts at a low catalyst concentration show a deactivation effect of the gasification reaction. Such an effect, however, takes place for a lesser number of catalysts and to a shorter extent than when the gasification of the same material is effected in steam at higher temperatures. In general, the hydroxides, acetates and carbonates do not show a substantial difference in their catalytic activity; the chlorides seem to be less efficient catalysts. The alkali metals are much more active catalysts than the alkaline earth metals.

FehlererKennung und Programmoptimierung in der ET-AAS durch zeitaufgelöste Signale (Direkte Elementspurenbestimmung in Harn: Cd, Co, Cr, Ni, Tl, Pb)

The direct determination of trace elements in urines with ET-AA-spectrometry leads to numerous systematic errors. Part of these errors can be discovered by time-resolved signals and can thereby be avoided. Contrary to the assumption that optimal results can be obtained via the signal area, it is often the measurement of the signal height, which is to be given preference (better ratio of atomic absorption signal/background signal). Phosphate-containing matrix modifiers cause systematic interferences; their use should therefore be avoided. The determination of cobalt traces with the ET-AA-spectrometry and with D2-background correction will always yield wrong values, if samples contain at the same time phosphorous oxygen compounds as well as alkali compounds. Previous Co-determinations which were carried out with this method, should therefore be controlled in a number of biotic matrices. When “Zeeman”-correction is used, such errors will not occur.

Effect of alkalies on the performance of blast furnace.

The influence of alkalies on the blast furnace operation has been discussed from the data collected from the Iron and Steel Co., Helwan, Egypt. The stability of the alkali compounds formed in the blast furnace was calculated from the thermodynamic data. The model of alkali circulation in the different zones of the furnace, as a function of temperature is proposed. Statistical analysis of alkalies from the input and output materials was calculated and discussed. The effect of alkalies on the partition of manganese and sulphur as well as on the rate of coke consumption was investigated. The relations between the alkali loadings, the basicity and the efficiency of alkali removal by the slag were discussed. Mathematical relations between these different parameters were given and correlated.

Catalytic water vapour gasification of carbon: Importance of melting and wetting behaviour of the ‘catalyst’

The melting and wetting behaviour of various alkali compounds (carbonates: Li 2CO 3, Na 2CO 3, K 2CO 3, Cs 2CO 3; halides: KF, KCl, KBr, NaCl; single potassium salts: KNO 3, K 2SO 4) without and with additives (V 2O 5, FeSO 4 · 7H 2O) on a polished surface of a polycrystalline graphite of high purity was studied during heating at 4 K min −1 to 900 °C in different atmospheres. It was found that all those catalyst raw materials which showed catalytic activity in earlier studies are low-melting and wet the graphite surface. This is especially true of mixtures of alkali chlorides (NaCl, KCl) with V 2O 5 and of K 2SO 4 with FeSO 4 · 7H 2O or other iron salts.

Thermochemistry of the alkali metal and alkaline earth-actinide complex oxides

After a brief discussion of the various techniques used for the preparation of actinide complex oxides, the present status of the thermochemistry of these compounds is reviewed. Perovskiterelated compounds with general formulae M II 3An VIO 6 , M II 2M' IIAn VIO 6 , M IAn VO 3 and M IIAn IVO 3 , as well as compounds of the type M IIAn VIO 4 , M I 2An VIO 4 , M I 2An VI 2O 7 and M I 4An VIO 5 , are especially considered as, in the case of those species, thermodynamic data are available for compounds of several actinides and/or several alkali and alkaline earth metals. The stabilities of the complex oxides are discussed with respect to the parent binary oxides and to the aqueous ions; trends as a function of the size of the alkali or the alkaline earth cation are presented. Suggestions for synthesis of some analogous compounds with heavier actinides are also discussed.

Conservation and Restoration of Natural Stone in Europe

Natural stone has always played a significant role in the construction of important European buildings. As early as ancient times and the Middle Ages, weathering of natural stone caused concern among master builders and architects. In those times, however, there was no understanding of the physical and chemical mechanisms responsible for stone decay or about the possibilities for optimum stone protection. Ancient times saw the application of natural resins as preservatives for natural stone. During the Middle Ages oily and waxy compounds were applied. As recently as the late 19th century compounds of hydroflouric acids and alkali silicates so-called water glass were used. Though well-intended, such measures frequently resulted in an acceleration rather than a reduction of the ongoing deterioration processes.

Transport-induced shifts in condensate dew-point and composition in multicomponent systems with chemical reaction

We present an analysis of partial heterogeneous condensation phenomena in multicomponent reacting systems, including previously neglected chemical element transport considerations. These phenomena, associated with the tendency of the chemical elements to preferentially “segregate” (according to the local temperature and the transport properties of the chemical species containing each element), are found to: (a) systematically “shift” the prevailing dew-point from that predicted purely thermodynamically, (b) systematically alter concentrations in the incipient condensate and (c) even influence the identity of a resulting single component condensate. Several distinct dew-points are shown to exist in such systems (depending upon one's operational definition or method of detection), and, as a result of transport constraints, the “sharp” locus between two chemically distinct condensates is systematically moved to a difference mainstream composition. These novel aspects of partial condensation-chemical vapor deposition (CVD) phenomena in multicomponent, chemically reacting systems are demonstrated using representative calculations and recent experiments on alkali compound condensation from the gaseous products of fossil fuel combustion. However, the phenomena illustrated here are rather general, and can be anticipated in other CVD-systems of technological importance (e.g. in semiconductor processing) by applying the concepts and methods outlined below.

Crystal chemistry of some addition compounds of alkali iodates with telluric acid

Five addition compounds of telluric acid with alkali iodates are described. Three of these compounds are orthorhombic and isotypic: RbIO3·Te(OH)6, KIO3·Te(OH)6, and NH4IO3·Te(OH)6. The crystal structure of this class of compounds has been solved with the potassium salt whose unit-cell dimensions are a = 14.30(1) Å, b = 6.734(5) Å, c = 8.711(5) Å, Pc21n (C92v). Z = 4. Crystal data are given for the two isotypic salts. The crystal structures of two other compounds have been determined. 2KIO3·Te(OH)6 is trigonal, R3̄, with the unit cell dimensions a = 6.500(5) Å, c = 25.717(8) Å, Z = 3 for the hexagonal description. NH4IO3·Te(OH)6·H2O is triclinic (P1̄) with a = 10.99(1) Å, b = 6.932(4) Å, c = 6.559(4) Å, α = 88.89(5), β = 90.88(5), γ = 104.48(5)°, and Z = 2. For these three different crystal structure determinations the final R values are, respectively, 0.047, 0.030, and 0.036. The first class of compounds described in this paper, MIO3·Te(OH)6 (M = K, Rb, NH4) is a new class of piezoelectric materials.

Aqueous catalyst systems for the water-gas shift reaction. 1. Comparative catalyst studies

A comparative study of both aqueous and nonaqueous catalysts - metal carbonates, alkali metal salts, and supported metal oxides - for the water-gas shift reacton utilized a pressurized aqueous batch reactor system. Test results showed that (1) alkali metal salts catalyze the water-gas shift reaction in the temperature range of 390/sup 0/-750/sup 0/F, (2) alkali metal salts and some transition metal salts are significantly more active than similar alkali earth compounds, (3) several alkali compounds can act as catalysts (or generate a catalytic species in situ) for the water-gas shift reaction in a pressurized aqueous system, (4) the cation need not be a metal, and (5) aqueous solutions of sodium carbonate may display activity levels similar to or higher than those of supported metal oxides in a pressurized system.

Quantitative determination of hafnium in mixtures of zirconium–hafnium hexachloro alkali compounds by neutron activation analysis and X-ray fluorescence

A procedure for the determination of Hf in both mixtures of HfCl4–ZrCl4 and A2HfCl6–A2ZrCl6, where A = Li, Na, K, Rb, or Cs, is described. The method involves conversion of the chlorocompounds into HfO2–ZrO2 mixtures and subsequent analysis by either X-ray fluorescence or neutron activation analysis. The two analytical techniques are compared with regard to accuracy and simplicity.

Pseudopotential calculations including core-valence correlation: Alkali compounds

Semiempirical pseudopotentials including core-polarization account quantitatively for core-valence correlation and give accurate results even for relativistic molecules. We discuss the main spectroscopic constants for molecular ions of the type A′A + and AH + (A′, A: Li to Cs) and for the molecules LiH, NaK and LiF.

Alkali compounds in Nigerian portland cement clinkers

Four out of the six Nigerian Portland cement clinkers contain alkali bearing compounds in the form of either single or double sulphates. An attempt has been made to identify these compounds and derive their compositions from SEM-EDXA study.

AES investigations of chemical composition of some alkali compounds

AbstractAuger electron spectroscopy is used as a quantitative and qualitative tool to investigate solid surfaces. Conventional quantitative analyses are based on the comparison of the Auger signal from the sample to that from pure standard. A detailed analysis of peak shape of Auger signal shows that the upper part of the derived Auger line (lower energy side) is strongly related to the chemical bonding whereas the lower part (high energy side) is nearly insensitive to the chemical effects.A calibration method for quantitative Auger spectroscopy based on the amplitude variation of the LVV Auger transitions of one element as a function of its chemical bonding within the compound is described. This method takes into account sample ‘matrix’ effects as well as all kinds of instrumental effects on the measured Auger signal.It has been also shown that AES can be used to make successful chemical analyses on alkali antimonides. A direct relation between electronic charge transfer between atoms and Auger peak shape has been observed, it is used to relate photoelectric quantum yield of SbKx compound to the ionicity of the Sb–K bond.

Pseudopotential calculations including core-valence correlation: Alkali compounds

Semiempirical pseudopotentials including core-polarization account quantitatively for core-valence correlation and give accurate results even for relativistic molecules. We discuss the main spectroscopic constants for molecular ions of the type A′A + and AH + (A′, A: Li to Cs) and for the molecules LiH, NaK and LiF.

A proper account of core-polarization with pseudopotentials: single valence-electron alkali compounds

A polarization potential is incorporated into semi-empirical and Hartree-Fock adjusted pseudopotentials. For molecules, the pseudopotentials become geometry-dependent. The omission of this effect has been the reason for too small R e values in earlier semi-empirical work. Very accurate results are obtained for the dimer and hydride ions of alkali elements up to K.