Weak Alkaline Medium Research Articles

Poly(styrene-divinylbenzene) copolymers with N-chlorosulfonamide functional groups as oxidants for arsenite ions in aqueous media — redox studies

Two macromolecular oxidants that were macroporous styrene/divinylbenzene copolymers containing N-chlorosulfonamide functional groups in the sodium form — RCl/Na (a macromolecular analog of chloramine-T) or in the hydrogen form — RCl/H (there is no analog among low-molecular compounds) were synthesized and used as oxidants of arsenites in dilute aqueous solutions. The reaction course was examined depending on stoichiometric ratios of reagents by special reductometric, potentiometric measurements at different pH values. In weak alkaline medium (pH ~11.5) the RCl/Na copolymer was ineffective as an As(III) oxidant, the reaction proceeded with difficulty, and the redox potential reached a negative value. In weak acidic medium (pH~3.0) the reaction proceeded efficiently enough, but the flat titration curve indicated the unfavorable kinetics of As(III) oxidation by means of RCl/H (despite the high redox potential in the reaction medium). In neutral medium (pH ~6.5) the reaction proceeded with the highest effectiveness. In this case the titration curve had a characteristic, classic shape, indicating the advantageous kinetics of As(III) oxidation by means of RCl/Na (despite the lower redox potential in the reaction medium).

Morphological classification of mesoporous silicas synthesized in a binary water–ether solvent system

Using diethyl ether as a co-solvent, a non-stable interface of biphasic oil–water system (the so-called oil–water two-phase (OWTP) system) was employed in the preparation of mesostructured silicas with diversified particle morphologies. By adjusting the molar ratios of H 2O:C 2H 5OC 2H 5:NH 3 · H 2O and the alkalinity of the OWTP system, several product morphologies could be obtained under different reaction conditions. On the other hand, different product morphologies with distinct structural properties could be obtained at a specific reaction condition, indicating that product morphology varied upon intrinsic characteristics of non-equilibrium processes in the system as well. There are six kinds of product morphologies in our results. In the biphasic region the morphotypes such as vesicles, slices, and spheres were widely distributed. Multi-lamellar fragments were formed under relatively strong alkaline conditions and at a high proportion of diethyl ether (>41%). bi-continuously phased fragments were observed in the weak alkaline conditions and medium proportion between diethyl ether and water. In the single-phase region, hexagonally ordered MCM-41, plain sheets of MCM-48, as well as smooth and plain slices with worm-like pore structures were formed with bi-modal pore-size distribution structure. Based on HRTEM analysis, these structural features were rationalized being derived from fragments that originated from the oil/water interface. Apparently, the product morphosynthesis resulted from a combination of fluid rheological distortions and reconstructive reaction fields. With a systematic approach we have established the reaction phase diagram of the system, which enabled us to define the structural properties and to classify the morphology of the products for nomenclatural purposes in studying OWTP systems.

Green Tea Polyphenols Function as Prooxidants To Activate Oxidative-Stress-Responsive Transcription Factors in Yeasts

Epigallocatechin gallate (EGCG) is the most abundant polyphenolic flavonoid in green tea. Catechin and its derivatives, including EGCG, are widely believed to function as antioxidants. Here we demonstrate that both EGCG and green tea extract (GTE) cause oxidative stress-related responses in the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe under weak alkaline conditions in terms of the activation of oxidative-stress-responsive transcription factors. GTE as well as EGCG induced the nuclear localization of Yap1 in S. cerevisiae, which was repressed by the addition of catalase but not by the addition of superoxide dismutase. The same phenomena were observed for the nucleocytoplasmic localization of Msn2 in S. cerevisiae and Pap1, a Yap1 homologue, in S. pombe. The formation of intramolecular disulfide bonds has been proposed to be crucial for the H(2)O(2)-induced nuclear localization of Yap1, and we verified the importance of cysteine residues of Yap1 in response to EGCG and GTE. Additionally, we show that EGCG and GTE produce H(2)O(2) in a weak alkaline medium. Finally, we conclude that tea polyphenols are able to act as prooxidants to cause a response to oxidative stress in yeasts under certain conditions.

Interactions of amphoteric amino phosphoric acids with calcium-containing minerals and selective flotation

Collecting properties of a new amphoteric collector (α-benzol amino benzyl phosphoric acid, BABP) for calcium-containing minerals were studied by micro-flotation tests and measuring mineral electrokinetic potentials and collector adsorption. The collector adsorption was confirmed by infrared spectroscopic characterization and adsorption determination. The results were interpreted based on solution chemistry calculations. BABP collector exhibited selectivity for fluorite and calcite in a weak alkaline medium. The increasing collecting power of BABP is apatite≪scheelite<calcite∼fluorite. Fluorite and calcite were positively charged while apatite and scheelite were negatively charged over a wide pH range. The collector addition caused a significant change in the zeta potential of the minerals, which correlated well with the floatability of the minerals. The monovalent anionic species were identified as the active components of amino phosphoric acids for collecting calcium-containing minerals. The chemisorption appeared to be the driving force for collector adsorption on fluorite, calcite and scheelite, with the extend of adsorption being determined by the site density of calcium on the minerals. With BABP as a collector, the flotation separation of calcite from apatite and fluorite from scheelite can be accomplished by careful control of flotation pH.

Determination of Nitrite in Foods by Single-Sweep Polarography

In an acid medium, nitrite diazotized with p-rosaniline and then coupled with 8-hydroxyquinoline in a weak alkaline medium produces azo compounds. The azo compounds produce a very sensitive polarographic wave at -0.70 V (versus the saturated calomel electrode). The height of the peak is linear with the concentration of nitrite in the range of 5 x 10(-9) to 5 x 10(-7) g/mL. The detection limit is 3 x 10(-9) g/mL. The electrochemical characteristics of the polarographic wave are also discussed. The method was used to determine nitrite in sausage. The results agree well with those obtained by spectrophotometry.

Comparative Studies of Hemicelluloses Solubilized during the Treatments of Maize Stems with Peroxymonosulfuric Acid, Peroxyformic Acid, Peracetic Acid, and Hydrogen Peroxide. Part 1. Yield and Chemical Characterization

Summary Treatment of the water-extracted maize stems with peroxymonosulfuric acid at 20 °C for 144 h, peroxyformic acid at 80°C for 6 h, peracetic acid at 50°C for 6 h, and 2% hydrogen peroxide at 45°C for 12 h at pH 1.5, 4.4, 9.5, 11.5, 12.0, and 12.6, respectively, solubilized 47.1%, 91.3%, 33.3%, 16.6%, 15.9%, 17.4%, 86.2%, 87.7%, and 91.3% of the original lignin, and hydrolysed or dissolved 12.1%, 99.1%, 4.5%, 2.7%, 3.1%, 3.1%, 63.3%, 64.7%, and 83.0% of the original hemicelluloses, respectively. Substantial lignins and hemicelluloses were degraded or released during the treatment with peroxyformic acid and alkaline peroxide at pH ≥ 11.5, while an insignificant effect on delignification and hemicellulose solubilization was observed by using peroxymonosulfuric acid, peracetic acid, and hydrogen peroxide in acidic, natural, and weak alkaline media. The optimum condition for extraction of hemicelluloses was found to use 2% H2O2 at 45°C for 12 h at pH 11.5–12.0, which yielded 63.3–64.7% of the original hemicelluloses having much lighter color than those obtained by peroxymonosulfuric acid and peracetic acid under conditions used and 2% H2O2 at pH 1.5, 4.4, 9.5, and 12.6. Xylose and arabinose were the major sugar constituents in these hemicellulose preparations, whereas glucose, galactose, mannose, rhamnose, and fucose were present as minor components. The α-ether linkages between lignin and hemicelluloses in the cell wall of maize stems were substantially cleaved during the treatment with 2% H2O2 at pH ≥11.5 as shown by a minimal amount of associated lignin (2.9–3.9%), rich in syringyl units, in the solubilized hemicelluloses.

Inhibition of chloride pitting corrosion of mild steel by sodium gluconate

The effect of gluconate (G) anion on the inhibition of chloride pitting corrosion of Delta vanadium steel has been studied using potentiodynamic and scanning electron microscopy (SEM) techniques. The effect of concentration of G ions, pH, potential scanning rate and composition of mild steel are discussed. The data show that complete protection of mild steel from pitting corrosion is achieved with a very low concentration of G ions in weak alkaline media. Pitting corrosion increases with increasing sodium gluconate (SG) concentrations due to a formation of soluble Fe–G complex. The critical pitting potential depends on the chloride and G ion concentrations, pH, scan rate and the composition of the steel. An increase of Mn% in the composition of the steel leads to the increase of the pitting corrosion potential towards the positive direction, i.e., increases the resistance to pitting corrosion. The presence of vanadium in the steel also increases its resistance to pitting corrosion.

C—The synthesis of CeO 2+ n· n H 2O nanolayers on silicon and fused-quartz surfaces by the successive ionic layer deposition technique

For the first time, the conditions of the synthesis of CeO 2+ n · n H 2O nanolayer synthesis, such as the concentration and pH of the reactant solutions, the duration of treatment with them, and the number of ion-deposition cycles on kinetics of the layer growth on a silicon surface, were investigated. The deposited layers were studied through the methods of ellipsometry, UV-Vis and FTIR spectroscopy. When cerium acetate and hydrogen peroxide in a weak alkaline medium were used as the reactants, the surface film undergoes regular linear growth and its thickness can be controlled at the level of less than a nanometer. The prepared layers were investigated after heating in air at temperatures in the 100–500°C range.

Spectrophotometric study of copper(II) ion complexes with cefaclor

Abstract The formation of complex ions between cefaclor and Cu 2+ has been investigated by ultraviolet spectroscopy. The conditions of formation of complex ions were studied in weak acidic, neutral and alkaline medium in the pH range from 5.60 to 11.05. The interaction between cefaclor and Cu(II) ion in acidic medium results in the formation of Cu(CEF) + complex and it is supposed that the ligand acts as zwitterion which is coordinated to the metal ion. This complex easily hydrolyzes giving a hydroxo complex Cu(OH)(CEF). The Job method, the molar ratios method and the method of relative recovery of complex species were applied and it was found that the stoichiometric ratio between cefaclor and Cu(II) is 1:1. The molar absorptivity ϵ / M −1 1 cm −1 = 2670 ± 35 at 300 nm and the consecutive concentration constant of the hydroxo complex log K 2 /M −1 1 = 9.13 ± 0.118, were determined at pH = 8.00 and at an ionic strength of μ = 0.1.

Palladium on alumina catalyst for glucose oxidation: reaction kinetics and catalyst deactivation

The paper presents a study on glucose oxidation over a modified palladium/alumina catalyst in a weak alkaline medium. The high reaction rates and complete conversion obtained are explained by non-uniform distribution of the active metal within the catalyst support and also by the raised number of Pd atoms on the active particles surface. Catalyst deactivation is described as a process caused by Pd-0 formation in the metal lattice accompanied by adsorption of the reaction products. The effects of catalyst mass, particle diameter, multiple use of the catalyst and initial glucose concentration on the conversion were investigated. The kinetic constants are determined using the single site Langmuir-Hinshelwood model.

Spectrofluorimetric determination of zinc in milk samples with tyrosine

A new method for the determination of zinc, based on the fluorescence of the zinc–tyrosine chelate in a weak alkaline medium, has been developed. The method allows the determination of 0.65–32.5 µg ml–1 of zinc and is relatively free from interferences. The method has been applied in the determination of zinc in food samples with satisfactory results.

Increasing the strength of green magnesia refractories by using combined binders

The effect of the pH of the lignosulfonate (LST) medium on the strength of the green and the qualitative parameters of magnesia parts is established. LST with a weak alkaline medium are recommended for periclase parts, and LST with a weak acid medium are recommended for chrome-containing parts. The effect of some modifying additions to LST is investigated with testing of it in batch production. Combined binders (mixtures of LST with sodium and ammonium bases) are shown to have a positive effect on the properties of the green and ready parts.

Crystallization of ferrisilicate molecular sieve in the presence of fluoride ions

The ferrisilicate molecular sieve analogue of the ZSM-5 was prepared from the weak alkaline medium (pH 8) in the presence of F- ions, which was confirmed by IR, X-ray powder diffraction, EPR.and29Si MAS NMR studies. The addition of F- ion in the preparation of metallosilicate molecular sieves could reduced the pH value of the reaction mixture, and prevent from the precipitation of metal ions which are sparingly soluble in strong alkaline media.

ChemInform Abstract: Synthesis and Characterization of Di‐ and Tritelluratoferrate(III) Complexes.

AbstractThe novel tellurato complexes (I) and (II) are obtained by reaction of H2TeO3, Fe(NO3)3, and Li2SO4 in weak or strong alkaline medium, respectively.

In Vitro and In Vivo Behaviour of Four Different 99(m)Tc-HEDP Complexes

According to absorption spectra, at least four different 99Tc-HEDP complexes [complex I (colorless), complex II (yellow), complex III (pink-red) and complex IV (brown)] were observed under various labeling conditions. Both pH and Sn (II)-HEDP concentration greatly influenced the formation of these complexes. In acidic or neutral media, complex II was the main product while in alkaline media complex III and complex IV were formed below concentration levels of 1 X 10(-3)M of Sn (II) and of 3 X 10(-3)M of HEDP. At high Sn (II)-HEDP concentrations complexes I and II were formed, while complexes III and IV were found at lower Sn (II)-HEDP concentrations in weak alkaline media. All four 99(m)Tc-HEDP complexes were stable against air oxidation until at least 6 hrs after preparation. Complexes I and II were stable against dilution by distilled water, while complexes III and IV were unstable and readily dissociated. In organ distribution studies high soft-tissue uptakes were observed with complexes III and IV, while complexes I and II had high bone-seeking properties.

Immobilization of aminoacylase by adsorption to tannin immobilized on aminohexyl cellulose.

The immobilization of aminoacylase (N-acylamino acid amidohydrolase, EC 3.5.1.14) was investigated by using tannin immobilized on aminohexyl cellulose. The most active immobilized aminoacylase was obtained when aminoacylase was adsorbed to the immobilized tannin in a weak alkaline medium containing sodium chloride and n-butanol at 37 degrees C. The activity of the immobilized tannin-aminoacylase complex per unit volume was five times higher than that of the DEAE-Sephadex-aminoacylase complex used for industrial production of L-amino acids in our plants. The half-life of the immobilized tannin-aminoacylase complex was 20 days under continuous operation at a high concentration of substrate; on the contrary, that of the DEAE-Sephadex-aminoacylase complex was 0.5 days.

Groupements protecteurs benzyloxycarbonyles substitues alcalinolabiles

Esters, carbonates, thiocarbonates and carbamates of p-hydroxybenzylcarbonylglycine have been prepared. Free glycine is regenerated in weak alkaline medium by hydrolysis of the acyloxy group followed by an 1–6 elimination. Generally, these compounds are more stable than Z-glycine in trifluoroacetic acid. A series of protected aminoacids and dipeptides has been prepared too. Dilute soda or hydrogen peroxide in ammonia rapidly cleave the protecting group.

Über die Wanderung der Carboxylatgruppe bei der Benzilsäureumlagerung. 26. Mitteilung über Reduktone und Tricarbonylverbindungen

AbstractThe benzilic acid rearrangement of ethyl α,β‐dioxo‐butyrate was studied by NMR.‐and UV.‐techniques. In weak alkaline media (pH &lt; 10) the ester group is hydrolyzed first, then the carboxylate group migrates to form methyltartronate. The migration of the carboxylate group was proved by radioactive labeling. At higher pH‐values (pH &gt; 11,5) the intakt ester group migrates, with ester hydrolysis occuring as a second step.

On the reaction of beta-mercaptopropionic acid, beta-diethylaminoethylmercaptan and cysteine with various isothiocyanates

AbstractBy treating β‐mercaptopropionic acid with aryl (aralkyl) isothiocyanates in weak alkaline medium, the authors have obtained the corresponding β‐(N‐aryl(aralkyl)‐thiocarbamoylthio)‐propionic acids which, heated 2 hours at 120°, yield the corresponding 3‐aryl(aralkyl)‐4‐oxo‐2‐thiono‐tetrahydrothiazines.

臨床分析化学の基礎的研究 (第2報)

Colorimetric determination of 4-acetamidoantipyrine in plasma was studied and the standard procedure was established. Its principle is based on the oxidative condensation of 4-aminoantipyrine (Emerson's reagent), produced from 4-acetamidoantipyrine by hydrolysis, with phenols in weak alkaline medium to yield an indophenol-type pigment. Of the various kind of phenolic compounds, the simple phenol was found to be the most suitable for this purpose. It has also been found that development of the color is constant and stable over a wide pH range employing borate buffer already reported by Lacoste, et al. A known amount of 4-acetamidoantipyrine added to plasma was measured, using the calibration curve by the standard procedure and the results were quite satisfactory.