The ionic product of water in highly concentrated sodium perchlorate solutions

The ionic product of water, pK(w)=-log[H(+)][OH(-)], has been determined in aqueous solutions of sodium perchlorate over the concentration range of 1.0-8.0 M at 25 degrees C from high-precision potentiometric titrations carried out in cells with liquid junction using both glass and hydrogen electrodes. The glass electrode results are systematically lower probably as a result of interference by Na(+) ions.     

Untersuchungen an Systemen aus Salzen und gemischten Lösungsmitteln. XXIV. [1]. Das System Magnesiumchlorid–Aceton–Wasser

Studies on systems of salts and mixed solvents. XXIV. System magnesium chloride—acetone—water Solubilities and parageneses of the solid phase of the system MgCl₂? H₂O? (CH₃)₂CO as well as densities and kinematic viscosities of saturated equilibrium solutions are presented for temperatures of 15, 25, 35, and 50°C. Two liquid phases exist in a wide range of concentration of the solvent mixture. In comparison with the analogous methanol system the addition of acetone does not result in the formation of solid MgCl₂ solvates containing acetone. Dehydration of MgCl₂ · 6 H₂O (bischofite) cannot be observed, either.     

Determination of trace elements in beach asphalts by neutron activation analysis

The feasibility of using trace multielement data obtained from neutron activation analysis to identify the source of crude oil residues was recently demonstrated. This paper presents the concentrations of Br, Co, Cr, Sb, Sc, Zn, and V/Ni, for 30 crude oil residues collected from beaches (beach asphalt), using 1 g samples. The method does not require chemical separation or post-irradiation concentration. The average standard deviation for the V/Ni ratio was ±0.39.     

Vascular endothelial growth factor as a biomarker for the early detection of cancer using a whole cell-based biosensor

Vascular endothelial growth factor (VEGF) is a cytokine and endothelial cell (EC) mitogen that has been studied for its role in angiogenesis of malignant tumors. Elevated quantities of VEGF in the serum and plasma of patients have been correlated with the presence of cancer and metastasis. Since VEGF induces hyperpermeability of EC monolayers, this protein can be detected in vitro with a whole cell-based biosensor. This biosensor consists of a confluent monolayer of human umbilical vein endothelial cells (HUVECs) attached to a cellulose triacetate (CTA) membrane of an ion-selective electrode (ISE). Previous studies regarding this biosensor have shown that when the biosensor was exposed to a model toxin, such as histamine, the response of the biosensor served as an indirect measurement of the presence of histamine. Similarly, the biosensor responds to the presence of VEGF, but is much more sensitive because VEGF is known to be 50,000-fold more potent than histamine when inducing EC hyperpermeability. The ISE response increased with increasing VEGF concentration. Since lower concentrations required more exposure time, the detection limit was established as a function of exposure time (2–10 h). The practical applicability of the biosensor was also established with cultured human melanoma cells WM793 (nonmetastatic) and 1205LU (metastatic). The resultant change in the potential values revealed significant production of VEGF from the 1205LU cells. A VEGF ELISA was performed to confirm the VEGF concentration in each sample. The biosensor closely predicted the concentrations determined through the ELISA. These results support the use of a cell-based ISE as a quick screening method for the presence of VEGF.     

Synthesis and crystal structures of (fulvalene)W(2)(SH)(2)(CO)(6), (fulvalene)W(2)(mu-S(2))(CO)(6), and (fulvalene)W(2)(mu-S)(CO)(6): low valent tungsten carbonyl sulfide and disulfide complexes stabilized by the bridging fulvalene ligand

Reaction of FvW(2)(H)(2)(CO)(6) with 2/8S(8) in THF results in rapid and quantitative formation of FvW(2)(SH)(2)(CO)(6). The crystal structure of this complex is reported and shows that the two tungsten-hydrosulfide groups are on opposite faces of the fulvalene ligand in an anti configuration. Nevertheless, treatment of FvW(2)(SH)(2)(CO)(6) (1) with PhN[double bond]NPh produces FvW(2)(mu-S(2))(CO)(6) (2) and Ph(H)NN(H)Ph. The crystal structure of the bridging disulfide, which cocrystallizes with 1 in a 2:1 ratio, is also described. Exposure of 2 equiv of *CrCp*(CO)(3) to 1 effects similar H atom transfers yielding 2 HCrCp*(CO)(3) and 2. Attempts to obtain crystals of the latter from solutions derived from this reaction mixture furnished a third product, FvW(2)(mu-S)(CO)(6) (3), which was analyzed crystallographically. The enthalpy of sulfur atom insertion into FvW(2)(H)(2)(CO)(6), yielding 1, has been measured by solution calorimetry.     

Sandia octahedral molecular sieves (SOMS): structural and property effects of charge-balancing the M(IV)-substituted (M = Ti, Zr) Niobate framework

Sandia octahedral molecular sieves (SOMS) is an isostructural, variable composition class of ion exchangers with the general formula Na(2)Nb(2-x)M(IV)(x)O (6-x)(OH)(x).H(2)O (M(IV) = Ti, Zr; x = 0.04-0.40) where up to 20% of the framework Nb(V) can be substituted with Ti(IV) or Zr(IV). This class of molecular sieves is easily converted to perovskite through low-temperature heat treatment (500-600 degrees C). This report provides a detailed account of how the charge imbalance of this Nb(V)-M(IV) substitution is compensated. X-ray powder diffraction with Rietveld refinement, infrared spectroscopy, thermogravimetric analysis, (23)Na MAS NMR, and (1)H MAS NMR were used to determine how the framework anionic charge is cation-balanced over a range of framework compositions. All spectroscopic evidence indicated a proton addition for each M(IV) substitution. Evidences for variable proton content included (1) increasing OH observed by (1)H MAS NMR with increasing M(IV) substitution, (2) increased infrared band broadening indicating increased H-bonding with increasing M(IV) substitution, (3) increased TGA weight loss (due to increased OH content) with increasing M(IV) substitution, (4) no variance in population on the sodium sites (indicated by Rietveld refinement) with variable composition, and (5) no change in the (23)Na MAS NMR spectra with variable composition. Also observed by infrared spectroscopy and (23)Na MAS NMR was increased disorder on the Nb(V)/M(IV) framework sites with increasing M(IV) substitution, evidenced by broadening of these spectral features. These spectroscopic studies, along with ion exchange experiments, also revealed the effect of the Nb(V)/M(IV) framework substitution on materials properties. Namely, the temperature of conversion to NaNb(1-x)M(IV)(x)O(3) (M = Ti, Zr) perovskite increased with increasing Ti in the framework and decreased with increasing Zr in the framework. This suggested that Ti stabilizes the SOMS framework and Zr destabilizes the SOMS framework. Finally, comparing ion exchange properties of a SOMS material with minimal (2%) Ti to a SOMS material with maximum (20%) Ti revealed the divalent cation selectivity of these materials which was reported previously is a function of the M(IV) substitution in the framework. A thorough investigation of this class of SOMS materials has revealed the importance of understanding the influence of heterovalent substitutions in microporous frameworks on material properties.     

Three different bonding modes of cyano groups in the coordination polymer [Cu(en)2(H2O)][Cu(en)2Ni2Cu2(CN)10]·2H2O (en is 1,2‐diaminoethane)

Partial reduction of the Cu^II ions in the aqueous system Cu^II–en–[Ni(CN)₄]^2? (1/1/1) (en is 1,2‐di­amino­ethane) yields a novel heterobimetallic mixed‐valence compound, poly­[[aqua­bis(1,2‐di­amino­ethane)copper(II)] [hexa‐μ‐cyano‐tetra­cyano­bis(1,2‐di­amino­ethane)­tricopper(I,II)­dinickel(II)] dihydrate], [Cu(C₂H₈N₂)₂(H₂O)][Ni₂Cu₃(CN)₁₀(C₂H₈N₂)₂]·2H₂O or [Cu(en)₂(H₂O)][Cu(en)₂Ni₂Cu₂(CN)₁₀]·2H₂O. The structure is formed by a negatively charged two‐dimensional array of the cyano complex [Cu(en)₂Ni₂Cu₂(CN)₁₀]_n^2n?, [Cu(en)₂(H₂O)]²⁺ complex cations and water mol­ecules of crystallization. These last are involved in a complicated hydrogen‐bonding system. The cyano groups act as terminal, μ₂‐bridging or μ₃‐bridging ligands.     

Dithiadiazolyls as heterocyclic chelators: a radical approach to coordination chemistry?

The ability of heterocyclic compounds to act as chelating ligands via the cleavage of a heterocyclic E–E (or E–E′) bond with concomitant formation of M–E (and M–E′) bonds is described with particular reference to the 7π heterocyclic dithiadiazolyl radicals, R

. These electron-rich ring systems form a diversity of structural bonding types in which the heterocyclic ring can formally act as a 2e⁻, 3e⁻, 5e⁻ or 6e⁻ donor ligand. These structural bonding modes are described through examples in which the heterocyclic ring interacts with halide anions, N atoms and particularly metal centres, forming monometallic, dimetallic and trimetallic complexes. The structural features which determine which compounds are likely to act as cyclic chelators are discussed and examples of thiadiazole, diselenadiazolyl and dithiole rings acting as cyclic chelators are given.     

Pervaporation separation of water/ethanol mixture by TGN/PSF blending membrane

The separation performance of plasticizer/polysulfone (TGN/PSF) pervaporation membrane was studied. The optimum amount of plasticizer (TGN) in PSF membranes improved the diffusion selectivity of water to ethanol, which was due to the increase in the permeate diffusion rate difference between water to ethanol molecules. On the other hand, the solubility selectivity of water to ethanol in PSF membrane showed a minor change with increasing the plasticizer content in TGN/PSF membrane. The feed ethanol concentration showed a significant influence on the degree of swelling as well as the separation performance of TGN/PSF membrane. It was found that the dominant factor of permeate transport through membranes was the diffusion rate difference, especially at high ethanol concentrations in feed. This study indicated that a good separation performance could be achieved at high ethanol concentrations in feed. This investigation also proves that the flexible polymer chain mobility, which was due to both the addition of TGN in the membrane and the swelling effect of the membrane at the high ethanol concentration in feed solution, strongly influences the separation properties of TGN/PSF membrane.