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At least 19 recordsLinked to original sources
PubMed1978

Mean activity coefficients for the simple electrolyte in aqueous mixtures of polyelectrolyte and simple electrolyte. V. Common counterion mixtures of alkali-metal dextransulfates with alkali metal chlorides.

Mean molal activity coefficients of simple electrolyte in aqueous solutions of Li, Na, K or Cs salts of dextransulfate (DS) with added LiCl, NaCl, KCl or CsCl are reported. The measurements were carried out by means of an electrochemical cell method using a cation exchange membrane as cation selective electrode and Ag/AgCl electrodes. For LiDS-LiCl, NaDS-NaCl and CsDS-CsCl systems the polymer concentration, mp, was varied from 0.0088 to 0.113 m and at a given mp the ratio X of the polymer to salt concentration was varied from 0.5 to 16. Due to the insolubility of KDS in high concentration of KCl, the measurements on KDS-KCl system were performed in the mp range of 0.0088--0.089 m and some of the smaller X values were omitted. The activity coefficient results are compared to Manning's limiting laws, the additivity rule, and to new limiting laws. The additivity rule can give an excellent representation of the data for all mp values when gammap is used as an adjustable parameter.

Chemical Phenomena↗
PubMed2000

Effect of alkali metal cationization and multiple alkali metal exchange on the collision-induced dissociation of loganic acid studied by electrospray ionization tandem mass spectrometry

Under electrospray ionization conditions loganic acid undergoes alkali metal (Li, Na and K) exchange and alkali metal cationization. Multiple exchanges of up to four alkali metal ions are observed. Different populations of metal exchanged species are produced during electrospray ionization. Collision-induced dissociation of ammonium cationized species is compared with that of metal cationized species to study the effect of metal cationization. Glycosidic cleavage and ring cleavages of aglycone and sugar moieties are the major fragmentation pathways observed during collision-induced dissociation. The fragmentations of the highly metal exchanged species indicate the opening of the pyran ring. Collision-induced dissociation of the various metal exchanged and metal cationized species also reveals the nature of the different populations. Copyright 2000 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1980

Effects of pH on frog gustatory responses to chloride salts of alkali-metal and alkali-earth-metal.

The pH effects on frog gustatory responses to alkali-metal and alkali-earth-metal chloride salts were examined using single fungi-form papilla preparations. Responses to 0.1-0.5 M NaCl were clearly dependent upon the pH of the stimulating solutions. The responses increased as the pH decreased from 6.5 to 4.5 and were almost completely suppressed at pH's above 6.5. There was no significant difference in the pH dependency of the response among alkali-metal chlorides. HCl solutions elicited only a poor response under conditions in which the water response was suppressed by the simultaneous presence of a low NaCl concentration. Responses to alkali-earth-metal chlorides varied in their pH dependency. Response to CaCl2 was slightly affected by pH changes from 4.5 to 9.0, response to SrCl2 was considerably suppressed in the alkaline region, and responses to BaCl2 and MgCl2 were strongly suppressed at pH's above 6.5. BeCl2 solutions showed less marked stimulating effects over the pH range tested. The differences in pH dependency described above suggest the existence of two kinds of receptor sites, one being pH-insensitive sites responsible for the calcium response and the other pH-sensitive sites responsible for the sodium response. A cross-adaptation test appeared to support this possibility. Assuming that the pH effect mentioned is related to changes in the state of ionization of the receptor molecule, the pKa of the ionizable group responsible for the sodium response was determined to be approximately 5.5.

Animals↗
PubMed2002

Efficient destruction of CF4 through in situ generation of alkali metals from heated alkali halide reducing mixtures.

Perfluorocarbons (PFCs) are the most potent green house gases that are very recalcitrant at destruction. An effective way of converting PFCs using hot solid reagents into safe products has been recently introduced. By investigating the thermal reductive destruction of tetrafluoromethane (CF4) we provided new insight and more physicochemical consideration on this novel process. The complete destruction of CF4was successfully achieved by flowing the gas through a heated reagent bed (400-950 degrees C) that contained powder mixtures of alkali halides, CaO, and Si. The silicon acted as a reducing agent of alkali halides for the in-situ production of alkali metals, and the calcium oxide played the role of a halide ion acceptor. The absence of any single component in this ternary mixture drastically reduced the destruction efficiency of CF4. The CF4 destruction efficiencies with the solid reagent containing the alkali halide, MX, increased in the order of Li approximately Na < K < Cs for alkali cations and I < Br < Cl < F for halide anions. This trend agreed with the endothermicity of the alkali metal generation reaction: the higher the endothermicity, the lower the destruction efficiency. Alkali metal generation was indirectly detected by monitoring H2 production from its reaction with water. The production of alkali metals increased with NaF, KF, and CsF in this order. The CsF/CaO/Si system exhibited the complete destruction of CF4 at as low as 600 degrees C. The solid product analysis by X-ray diffraction (XRD) showed the formation of CaF2 and the depletion of Si with black carbon particles formed in the solid reagent residue. No CO/CO2 and toxic HF and SiF4 formation were detected in the exhaust gas.

Air Pollution↗
PubMed1983

Effect of heavy metals and alkali metals on L-leucine uptake by human blood platelets.

The transport of L-leucine into human blood platelets was characterized as a function of time and amino acid concentration in the medium. Inhibition analyses showed that L-leucine uptake can be only partially inhibited by other amino acids including those which are believed to be transported by the same L system. When Cu2+, Zn2+, Mg2+, Co2+, Fe2+, Ba2+, or Cd2+ were introduced into the transport medium to the final concentrations of 2.5 and 5.0 mM, they inhibited significantly the L-leucine uptake into platelets. In contrast, the initial rate of L-leucine uptake was enhanced by Cu+ ions. Ceruloplasmin, a copper transporting protein, caused almost a complete inhibition of L-leucine uptake.

Adult↗
PubMed1997

Metallohosts Derived from the Assembly of Sugars around Transition Metals: The Complexation of Alkali Metal Cations.

The diacetone glucose (DAGH, 1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose) monoanion DAG binds as a terminal alkoxo ligand to a variety of transition metals. When it is used in excess, with respect to the oxidation state of the metal, homoleptic anionic complexes [M'(DAG)(6)](3)(-) are formed. Such complexes contain oxygen-rich cavities between pairs of DAG ligands appropriate for binding alkali metal cations. The anionic complexes have been obtained by using [Li(DAG)], 1, and [Na(DAG)], 2, whose syntheses and characterization are reported here. The reaction of 1 and 2 with [V(DAG)(3)] gave [V(DAG)(6)Li(3)], 3, and [V(DAG)(6)Na(3)], 4, respectively. An alternative synthesis of 3 and 4 involves the metathesis reaction of 1 and 2 with [VCl(3)(thf)(3)]. This strategy also led to the synthesis of [Cr(DAG)(6)Li(3)], 5, and [Ti(DAG)(6)Li(3)], 6. Three pairs of DAG shape a cavity appropriate for three lithium cations in the case of complexes 3, 5, and 6; a cavity is formed for three sodium cations in the case of 4, where the alkali cation is in a tetrahedral O(4) environment. In the anionic manganese derivative [Mn(Cl)(DAG)(4)](3)(-), the four DAG units arrange in such a way as to bind four Li cations, which form a cationic cage [Mn(Cl)(DAG)(4)Li(4)](+), and Cl(-) is bound inside as [Mn(Cl)(DAG)(4)Li(4)(&mgr;(4)-Cl)], 7. Crystallographic details: 4, prism, P2(1), a = 14.735(10) Å, b = 15.033(9) Å, c= 21.021(10) Å, beta = 107.34(2) degrees, V= 4445(5) Å(3), Z = 2, and R = 7.60; 5, prismatic, C2, a = 22.671(9) Å, b = 18.785(5) Å, c = 13.886(4) Å, beta = 126.39(2) degrees, V= 4761(3) Å(3), Z = 2, and R = 7.32; 6, prismatic, P2(1), a= 13.888(5) Å, b = 18.750(5) Å, c= 17.933(5) Å, beta = 91.84(2) degrees, V = 4667(2) Å(3), Z = 2, and R = 8.75; 7, prismatic, P2(1), a = 13.306(7) Å, b= 21.311(11) Å, c = 13.376(6) Å, beta = 95.01(2) degrees, V = 3779(3) Å(3), Z = 2, and R = 9.33.

Journal Article↗
PubMed2006

Inverse aggregation behavior of alkali-metal triazenides.

Higher aggregated alkali-metal compounds are usually obtained with increasing radius of the metal. Alkali-metal salts derived from the sterically crowded triazenido ligand Tph2N3H [Tph = C6H3-2,6-(C6H2-2,4,6-iPr3)2] do not obey this principle. Interestingly, these compounds show inverse aggregation behavior in the solid state: the potassium and cesium salts crystallize as discrete monomers in which the cations interact with flanking arene rings of the diaryltriazenido ligands, whereas the lithium derivative is dimeric with a more conventional heteroatom-bridged structure.

Journal Article↗
PubMed1984

Neuropsychiatric manifestations of alkali metal deficiency and excess.

The alkali metals from the Group IA of the periodic table (lithium, sodium, potassium, rubidium, cesium and francium) are reviewed. The neuropsychiatric aspects of alkali metal deficiencies and excesses (intoxications) are described. Emphasis was placed on lithium due to its clinical uses. The signs and symptoms of these conditions are characterized by features of an organic brain syndrome with delirium and encephalopathy prevailing. There are no clinically distinctive features that could be reliably used for diagnoses. Sodium and potassium are two essential alkali metals in man. Lithium is used as therapeutic agent in bipolar affective disorders. Rubidium has been investigated for its antidepressant effect in a group of psychiatric disorders. Cesium is under laboratory investigation for its role in carcinogenesis and in depressive illness. Very little is known of francium due to its great instability for experimental study.

Cesium↗