Search results for "hydroxide"
showing 10 items of 317 documents
Determination of tyrosine through a FIA-direct chemiluminescence procedure.
2003
A new FI-direct chemiluminescence method is proposed for the determination of tyrosine, based on the oxidation of the amino acid by K(3)Fe(CN)(6) in potassium hydroxide medium, at room temperature and enhanced by the presence of beta-cyclodextrin and formic acid. The dynamic range was linear over the range 1.0-10.0 mgl(-1). A large study of the influence of foreign compounds was performed, including amino acids; and, the method showed high selectivity. The reproducibility between days resulted in a rsd (in slope%) of 4.8 and the repeatability with a rsd (n=50, 10.0 mgl(-1)) of 3.1%, the LOD (s/n=3) was 50 mugl(-1) and sample throughput 98 h(-1).
O-Alkylation of a lignite humic acid by phase-transfer catalysis
2006
A mild phase-transfer catalytic reaction has been conducted to O-alkylate the acidic functions of a lignite humic acid (HA), using tetrabutylammonium hydroxide as the phase-transfer catalyst. The HA acidic functional groups were made to react, in tetrahydrofuran, by nucleophilic substitution with several alkyl halides-methyl iodide, and ethyl, propyl, and butyl, and benzyl bromide. The occurrence of the O-alkylation reaction was assessed by elemental analysis and 1H NMR, CPMAS 13C NMR, and FTIR spectroscopy. Bonding of alkyl groups increased the carbon and hydrogen content and the H/C ratios of all the humic reaction products. Increased nitrogen in the reaction products suggested incomplete…
Effective Removal and Mineralization of 8-Hydroxyquinoline-5-sulfonic Acid through a Pressurized Electro-Fenton-like Process with Ni−Cu−Al Layered Do…
2020
Ni−Cu−Al layered double hydroxide (Ni−Cu−Al LDH) was proposed as an electro‐Fenton‐like catalyst for 8‐hydroxyquinoline‐5‐sulfonic acid (8‐HQS) removal in water. The properties of the prepared catalysts were characterized by using X‐ray, SEM and EDAX analyses. The effect of numerous operative parameters on the removal of 8‐HQS and total organic carbon (TOC) was studied. Very high level removal of both 8‐HQS and TOC (87 and 79 %, respectively) were obtained by using a pressurized electro‐Fenton‐like process (PrEFL‐LDH) at P=10 bars, using a Ti/IrO2‐Ta2O5 anode for 6 h. The process presented good performances in a large range of pH (3–10) and gave better removals of 8‐HQS and TOC with respect…
Umsetzung von amino-aziminen mit basen
1980
Abstract Amino-azimines of type (1) react at room temperature with bases (ammonia, aliphatic amines, hydrazine and methyl-hydrazine, aqueous/ethanolic sodium hydroxide) by cleavage of the to the and the NNN moieties (azide).
A Mössbauer study of the crystalline structure of the passive film formed on iron in aqueous sulfate solution containing sulfite in low concentration
1993
Electrochemically induced passivation of evaporated, enriched 57Fe in 0.5 mol dm−3 Na2SO4 + 0.001 mol dm−3 NaHSO3 aqueous solution (pH 6.5) was followed by conversion electron Mossbauer spectroscopy. The transformation of amorphous iron oxide or hydroxide into crystalline γ-FeOOH could be observed with the increase of the polarization time. The comparison of the original quantity of evaporated, enriched 57Fe layer on the surface of the samples with the dissolved iron, measured in the solutions after the polarization, proved the existence of pitting corrosion at this pH.
Bulk pre-reactional transformations preceding the thermal decomposition of calcium hydroxide into oxide
1990
The present paper is an extended abstract which should be considered as an introduction to the papers already published by us on this new topic. An extended synthesis of these papers was given in the lecture. The original information introduced here is the figure. It is a PH2O vs. T diagram which gives the pre-reactional domain between the stability domains of calcium hydroxide and calcium oxide. Chemical reactions are proposed as an interpretation of the observed pre-reactional transformations.
Untersuchungen zum oxidativen Abbau nativer Cellulose, 2. Einfluß der Alkalibehandlung auf die Viskositäts-Molekulargewichts-Beziehungen
1974
Um die Kinetik des oxidativen Abbaus nativer Cellulose viskosimetrisch verfolgen zu konnen, mussen neue [η]-M-Eichbeziehungen aufgestellt werden, da die Behandlung der Cellulose mit konzentriertem Alkali den Staudingerindex [η] erniedrigt, ohne das Molekulargewicht M zu verandern. Es wurden zwei Reihen oxidativ abgebauter, verschieden lange mit Alkali vorbehandelter Cellulosen hergestellt und an diesen die Konstanten der Kuhn-Mark-Houwink-Gleichung fur die Cellulosenitrate in Aceton und die Cellulosen in Cuoxam (Cu(NH3)4(OH)2) durch Vergleich mit Lichtstreuungsmessungen bestimmt. For kinetic studies of cellulose degradation by molecular oxygen it is necessary to establish new [η]-M-relation…
<title>Cerium-containing counter electrodes for transparent electrochromic devices</title>
1997
Films of Me-Ce oxide (Me: Ti, Zr, Sn, W) and of Ni-Ce hydroxide were produced by reactive magnetron co-sputtering. Li intercalation in Me-Ce oxide, and H exchange in Ni-Ce hydroxide, were accomplished electrochemically. Electrochromism was quenched in proportion with the Ce content in Me-Ce oxide. Films of Zr-Ce (and to some extent Ti-Ce) oxide were able to serve as fully transparent counter electrodes, of much interest for transparent electrochromic devices. In Ni-Ce hydroxide, the Ce addition enhanced the capacity for charge exchange.
ChemInform Abstract: Continuous Hydrothermal Synthesis of Nanometric BaZrO3in Supercritical Water.
2008
Abstract Nanocrystalline barium zirconate (BaZrO 3 ) was synthesized using a hydrothermal synthesis process working in supercritical conditions and in a continuous way. By this method, we succeeded in the continuous and rapid production of nanopowders. As a preliminary work three barium precursors have been investigated: barium hydroxide (Ba(OH) 2 ), barium acetate (Ba(CH 3 COO) 2 ) and barium nitrate (Ba(NO 3 ) 2 ). Two of them (Ba(CH 3 COO) 2 and Ba(NO 3 ) 2 ) led to the pure perovskite phase. Then an experimental design has been conducted in order to determine the influence of the experimental parameters on the crystallinity and the grain size of the final product.
The initial stages of the heterogeneous degradation of alkali cellulose by oxygen in relation to the morphology of native cotton cellulose
2007
Treatment of cotton cellulose with sodium hydroxide solutions of varying concentration over extended periods in the absence of oxygen markedly decreases the intrinsic viscosity of both the cellulose in cuoxam and its cellulose trinitrate derivative (CTN) in acetone. Light-scattering measurements show that the molecular weight does not change while the radius of gyration decreases and the second virial coefficient increases. The narrow molecular weight distribution of the native cotton is still maintained. Mild oxidation first causes the intrinsic viscosity to increase. At more prolonged oxidation times the viscosity decreases. These results are interpreted by an intramolecular cross-linking…