Mixture Of HCl Research Articles

In situ transesterification of highly wet microalgae using hydrochloric acid

This study addresses in situ transesterification of highly wet microalgae with hydrochloric acid (HCl) as a catalyst. In situ transesterification was performed by heating the mixture of wet algal cells, HCl, methanol, and solvent in one pot, resulting in the fatty acid methyl ester (FAME) yield over 90% at 95°C. The effects of reaction variables of temperature, amounts of catalyst, reactant, and solvent, and type of solvents on the yield were investigated. Compared with the catalytic effect of H2SO4, in situ transesterification using HCl has benefits of being less affected by moisture levels that are as high as or above 80%, and requiring less amounts of catalyst and solvent. For an equimolar amount of catalyst, HCl showed 15wt.% higher FAME yield than H2SO4. This in situ transesterification using HCl as a catalyst would help to realize a feasible way to produce biodiesel from wet microalgae.

DSC and HPLC Studies of Some Common Antidiabetic and Antihypertensive Drugs

Now-a-days, a significant percentage of our population suffers from diabetes, hypertension and various inflammatory conditions. In such cases antihypertensive, antidiabetic and anti inflammatory drugs are prescribed concomitantly. Therefore, there is a possibility to have drug-drug interactions which may cause various complications to the patients or may be beneficial too. So study of drug-drug interaction is very important. To attain this objective, equimolar homogeneous mixture of naproxen, losartan potassium and pioglitazone HCl (mixture-1) and mixture of lercanidipine, captropril, naproxen and glimepiride (mixture-2) were studied by DSC (differential scanning calorimetry) and HPLC. DSC studies revealed that there was no interaction among naproxen, losartan potassium and pioglitazone HCl but same interaction was observed among lercanidipine, captropril, naproxen and glimepiride. The results obtained from DSC were further verified by HPLC. However, further studies are needed to make any conclusive remarks at this point. In future, the drug-drug interactions involving these molecules will be quantitatively evaluated for more precise predictions of in vivo drug-drug interactions. DOI: http://dx.doi.org/10.3329/bpj.v17i2.22326 Bangladesh Pharmaceutical Journal 17(2): 123-127, 2014

Mechanisms and rates of proton transfer to coordinated carboxydithioates: studies on [Ni(S2CR){PhP(CH2CH2PPh2)2}](+) (R = Me, Et, Bu(n) or Ph).

The complexes [Ni(S2CR)(triphos)]BPh4 (R = Me, Et, Bu(n) or Ph; triphos = PhP{CH2CH2PPh2}2) have been prepared and characterised. X-ray crystallography (for R = Et, Ph, C6H4Me-4, C6H4OMe-4 and C6H4Cl-4) shows that the geometry of the five-coordinate nickel in the cation is best described as distorted trigonal bipyramidal, containing a bidentate carboxydithioate ligand with the two sulfur atoms spanning axial and equatorial sites, the other axial site being occupied by the central phosphorus of triphos. The reactions of [Ni(S2CR)(triphos)](+) with mixtures of HCl and Cl(-) in MeCN to form equilibrium solutions containing [Ni(SH(S)CR)(triphos)](2+) have been studied using stopped-flow spectrophotometry. The kinetics show that proton transfer is slower than the diffusion-controlled limit and involves at least two coupled equilibria. The first step involves the rapid association between [Ni(S2CR)(triphos)](+) and HCl to form the hydrogen-bonded precursor, {[Ni(S2CR)(triphos)](+)HCl} (K) and this is followed by the intramolecular proton transfer (k) to produce [Ni(SH(S)CR)(triphos)](2+). In the reaction of [Ni(S2CMe)(triphos)](+) the rate law is consistent with the carboxydithioate ligand undergoing chelate ring-opening after protonation. It seems likely that chelate ring-opening occurs for all [Ni(S2CR)(triphos)](+), but only with [Ni(S2CMe)(triphos)](+) is the protonation step sufficiently fast that chelate ring-opening is rate-limiting. With all other systems, proton transfer is rate-limiting. DFT calculations indicate that protonation can occur at either sulfur atom, but only protonation at the equatorial sulfur results in chelate ring-opening. The ways in which protonation of either sulfur atom complicates the analyses and interpretation of the kinetics are discussed.

Sequential separation of ultra-trace U, Th, Pb, and lanthanides using a simple automatic system.

Uranium, thorium, lead, and the lanthanides were automatically and sequentially separated with a single anion-exchange column. This separation was achieved using eluents consisting of a simple and highly pure acid mixture of HCl, HNO3, acetic acid, and HF. The elements of interest were separated from the major constituents, which included alkaline metal elements, alkaline earth metal elements, and iron. This simple and automatic system is driven with pressurized nitrogen gas and controlled using a computer program. An optimized separation was accomplished under the following conditions: a 50 mm long and 2 mm diameter column, 11 μm diameter anion-exchange resin, and a 35 μL min(-1) flow rate. Using this system, 50 ng of varied elements in a 100 μL feed solution were perfectly separated within 5 h with >400 decontamination factors and >95% yield. In order to evaluate the performance of this system, a reference powdered rock sample was separated using this system. Abundances of objective elements, including 0.23 ng of lutetium, were accurately determined without corrections of chemical recovery yield or subtraction of the process blank. This separation technique saves time and effort for chemical processing, and is useful for ultra-trace quantitative and isotopic analyses of elements in small environmental samples.

Reaction of Hydrothermally Altered Volcanic Rocks in Acid Solutions

Rock matrix stimulation has been used to clean, to recover and to enhance well productivity in oil systems. Recently, for the same purposes this methodology began to be applied in geothermal systems. In order to investigate the solubility of altered volcanic rocks in acid solution used in rock matrix stimulation; experiments were carried out on samples of igneous hydrothermal altered rocks from the Los Humeros geothermal reservoir. Industrially, the common acid solutions used during acid well stimulation are HCl 10% and a mixture of HCl 10% and HF 5%. In this work, experiments were conducted in the laboratory using the referred acid solutions at atmospheric pressure and temperature of 110 ± 5°C. The chemistry, the mineralogy and the permeability of selected rocks from Los Humeros geothermal field were determined before and after the reaction with each acid solution. Mineral dissolution is selective and depends on the permeability of the rocks, the type and the intensity of hydrothermal alteration. As it is expected, Calcite readily reacts with acids leaving empty cavities, veins and micro fractures (worm holes). Calc-silicates are resistant to acid solutions. If Calcite is absent dissolution of minerals is observed in the external surfaces of the specimen in contact with the acid solution giving rise to a rough texture and leaving the rock matrix unreacted

Two novel Cu(II) complexes: Synthesis, structure and application in C–H bond activation

Two novel Cu(II) complexes [Cu2(H2L)2(3,5-pyridinedicarboxylic)(H2O)]·2NO3·2H2O (1) and [Cu(2,2′-bipy)(ad)1.5]·H3O·2H2O (2) (H2L=2,6-di-(5-methyl-1H-pyrazol-3-yl)pyridine, H2ad=hexane diacid) were synthesized and characterized by elemental analysis and IR spectra. Their catalytic performances were studied in cyclohexane (Cy) oxidation at mild condition. The total TON (turn over number) value raised from 61 to 271 with the addition of HNO3 promoted by complex 2, while from 0 to 143 by adding the mixture of HCl and lactic acid by complex 1.

Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate.

Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm2 using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si.

Comparative evaluation of the high-temperature fusion and the autoclave dissolution of process concentrates upon gravimetric determination of palladium

Various techniques for decomposition of process concentrates with a high content of palladium, such as fusion with potassium pyrosulfate and dissolution in autoclaves, with the purpose of the following gravimetric determination of palladium are described. It is shown that the optimal method for transferring the sample into the solution is its dissolution in a mixture of HCl and HNO3 (3: 1) using analytical autoclaves. The conditions of the autoclave dissolution (the composition of the acid mixture, the temperature, and the dissolution time) are determined. The relative standard deviation of the analysis results is 0.3% for a content of palladium of 60–80%.

Development of tertiary thioamide derivatives to recover palladium(II) from simulated complex chloride solutions

Two thioamide derivatives, N-methyl-N-phenyl-octanthioamide (MPHTA) and N-methyl-N-cyclohexyl-octanthioamide (MCHTA), were synthesized from their amide analogues, adequately characterized, and systematically evaluated as extractants for palladium(II) from chloride media. In sequence of previous research, which revealed the adequacy of both compounds, when dissolved in toluene, to efficiently recover Pd(II) from a wide range of differently concentrated hydrochloric acid solutions, the Pd(II) solvent extraction performance of both MPHTA and MCHTA dissolved in commercial diluents is evaluated in this work. Additionally, results obtained on successive extraction–stripping cycles, involving thiourea as stripping agent, confirm the robustness and stability of these Pd(II) solvent extraction systems, even when commercial diluents are employed. Equilibrium extraction isotherms, obtained for both compounds in toluene, show a high Pd(II) loading capacity. Selectivity data has been collected for complex 4.0M and 6.0M HCl mixtures containing two, three, four or five metal ions — palladium(II), platinum(IV), rhodium(III), aluminum(III), and iron(III). Fe(III) is the only metal that affects Pd(II) extraction of both MPHTA and MCHTA, as Pd(II) distribution ratios are significantly reduced; on the other hand, the other metals are practically not extracted. These selectivity results are encouraging from a practical point of view, since both extractants may prove suitable to efficiently and selectively recover Pd(II) from hydrometallurgical solutions coming from the leaching of secondary raw material sources.

ChemInform Abstract: Chirality and Polarity in the f‐Block Borates M4 [B16O26(OH)4 (H2O)3Cl4] (M: Sm, Eu, Gd, Pu, Am, Cm, and Cf).

AbstractThe title compounds are prepared from mixtures of MCl3 (M: Sm, Eu, Gd, Pu, Am, Cm, and Cf), H3BO3, and HCl (autoclave, 240 °C, 7 d, 30—40% yield).

Evaluating the efficiency of spectral resolution of univariate methods manipulating ratio spectra and comparing to multivariate methods: An application to ternary mixture in common cold preparation

Simple, accurate, and selective methods have been developed and validated for simultaneous determination of a ternary mixture of Chlorpheniramine maleate (CPM), Pseudoephedrine HCl (PSE) and Ibuprofen (IBF), in tablet dosage form. Four univariate methods manipulating ratio spectra were applied, method A is the double divisor-ratio difference spectrophotometric method (DD-RD). Method B is double divisor-derivative ratio spectrophotometric method (DD-RD). Method C is derivative ratio spectrum-zero crossing method (DRZC), while method D is mean centering of ratio spectra (MCR). Two multivariate methods were also developed and validated, methods E and F are Principal Component Regression (PCR) and Partial Least Squares (PLSs). The proposed methods have the advantage of simultaneous determination of the mentioned drugs without prior separation steps. They were successfully applied to laboratory-prepared mixtures and to commercial pharmaceutical preparation without any interference from additives. The proposed methods were validated according to the ICH guidelines. The obtained results were statistically compared with the official methods where no significant difference was observed regarding both accuracy and precision.

Surface Chemistry of GaAs(100) and InAs(100) Etching with Tartaric Acid

Incorporating substrates with higher charge mobilities than Si and Ge in metal-oxide-semiconductor field-effect transistors (MOSFETs) would extend the scaling of this device architecture. III-V semiconductors are candidates, and etching and passivation processes are needed that are selective and yield smooth surfaces. The (100) face of III-V compounds contains both electron-deficient group III (Ga, In) atoms and electron-rich group V (P, As, Sb) atoms. Etching InP(100) in a mixture of HCl and H2O2 chlorinates the In (group III) atom forming a soluble product [1,2], yet the P (group V) atom is more reactive and is depleted from the surface [3]. α-Hydroxy acids (lactic, citric, malic, and tartaric) have been shown to bind to the group III atom [3] and could promote more uniform etching. This paper compares the surface chemistry of GaAs and InAs after etching in HCl and H2O2 mixtures with and without tartaric acid.

Pt Etching Method at Low Temperature Using Electrolyzed Sulfuric Acid Solution

Recently, in the semiconductor manufacturing industry, NiPt silicide with high conductivity is adopted. However, when removing the NiPt residues in NiPt silicide processing, there is a possibility to damage other metals and silicide. Removal of residual substances must be done with special care. As a conventional method, processing by SPM has been reported by Chur [1]. However, when Pt content is 10% or more, in this method, the wafers must be processed at 150°C for a long period of time. Then, this method may damage a metal gate and silicide. As another method, aqua regia can be used. However, in this method, it takes long time to dissolve NiPt. This paper reports, newly develped Pt etching method using one-step processing of ESA (Electrolyzed Sulfuric Acid) and HCl, and two-step processing using ESA and HCl mixture after HNO3 and H2O2 mixture. This method can treat NiPt silicide at lower temperature within a shorter time than in conventional methods.

Electrophysical parameters and concentrations of active particles in the plasma of HCl mixtures with inert and molecular gases

Electrophysical parameters in HCl-Ar, HCl-H2, and HCl-Cl2 mixtures are studied under conditions of the direct-current (DC) glow discharge. It is shown that there is no increasing in the concentration of atomic chlorine in HCl-Ar and, in HCl-H2 and there are no significant changes in the kinetics of atomicmolecular processes and, therefore, in the balance of neutral particles in the plasma. The increase in the concentration of admixture gas in HCl-Cl2 is accompanied by the monotonic increase in the concentration of chlorine atoms and the density of their flux to the surface that bounds the plasma volume.

Morphological Characteristics of W-Nanowires after Selective Etching

An eutectic NiAl–1.5 at.% W alloy prepared by using directionally solidified (DS)was employed as a source for producing W-nanowires. Several growth rate of 8,15,25/s was respectively used at a temperature gradient of ~240 K/cm in a Bridgman-type directional solidification furnace. A combined stability diagram was applied to predict proper conditions for the selective dissolution of NiAl matrix to get W-wires. Etching in a mixture of HCl:H2O2 released parallel aligned W-nanowires with a wire diameter of ~500 nm. Different morphologies, such as nanobelts, lotus-shaped, conical of W-nanowires are obtained at the different conditions.

A comparative study of different aspects of manipulating ratio spectra applied for ternary mixtures: Derivative spectrophotometry versus wavelet transform

This work represents a comparative study of different aspects of manipulating ratio spectra, which are: double divisor ratio spectra derivative (DR-DD), area under curve of derivative ratio (DR-AUC) and its novel approach, namely area under the curve correction method (AUCCM) applied for overlapped spectra; successive derivative of ratio spectra (SDR) and continuous wavelet transform (CWT) methods. The proposed methods represent different aspects of manipulating ratio spectra of the ternary mixture of Ofloxacin (OFX), Prednisolone acetate (PA) and Tetryzoline HCl (TZH) combined in eye drops in the presence of benzalkonium chloride as a preservative. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs. The proposed methods were validated according to the ICH guidelines. A comparative study was conducted between those methods regarding simplicity, limitation and sensitivity. The obtained results were statistically compared with those obtained from the reported HPLC method, showing no significant difference with respect to accuracy and precision.

Application of Transition‐Metal Complexes in Cyclohexane Oxidation: Synthesis, Structure, and Properties of Copper and Nickel Complexes with a Pincer N‐Heterocyclic Ligand

AbstractA series of coordination complexes, [CuCl2(H2L)] (1), [Ni(HL)2]⋅4 CH3CH2OH (2), [Cu(H2L)(dipic)]⋅0.5 HOCH2CH2OH⋅ 2 H2O (3), and [Ni(H2L)(dipic)]⋅0.5 HOCH2CH2OH⋅2 H2O (4) (H2L=2,6‐di(5‐methyl‐1H‐pyrazol‐3‐yl)pyridine, H2dipic=2,6‐pyridinedicarboxylic acid) are synthesized from bipyrazolyl derivative ligands. All of the complexes have been characterized by elemental analysis, IR and UV/Vis spectroscopy, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. Structural analyses reveal that the H2L ligand in complexes 1–4 connects with one metal center in a tridentate manner. In addition, these complexes are potential catalysts in cyclohexane (Cy) oxidation with an acidic mixture of HCl and lactic acid. A putative mechanism for Cy oxidation promoted by complex 2 is also proposed.

One step synthesis of silver nanowires used in preparation of conductive silver paste

For mass preparation of conductive silver paste, a convenient approach to synthesize silver nanowires (Ag NWs) is presented. Monodisperse Ag NWs with ca. 40 nm in diameter and over 10 μm in length were successfully obtained in high yield only by heating a mixture of AgNO3, poly(vinyl pyrrolidone), ethylene glycol and HCl prepared previously. This method not only simplifies the conventional polyol process but also extremely improves its repeatability. More important, the patterns fabricated with the Ag NWs naturally have a high conductivity, up to ca. 13 % of bulk silver, due to the cross-linked network structure formed by accumulation of nanowires. The conductivity even can be improved to 41 % of bulk silver conductivity through a chemical sintering at room temperature, which makes us believe that the Ag NWs could be broadly applied in preparation of conductive paste.

Electrochemically deposited gallium oxide nanostructures on silicon substrates

We report a synthesis of β-Ga2O3 nanostructures on Si substrate by electrochemical deposition using a mixture of Ga2O3, HCl, NH4OH, and H2O. The presence of Ga3+ ions contributed to the deposition of Ga2O3 nanostructures on the Si surface with the assistance of applied potentials. The morphologies of the grown structures strongly depended on the molarity of Ga2O3 and pH level of electrolyte. β-Ga2O3 nanodot-like structures were grown on Si substrate at a condition with low molarity of Ga2O3. However, Ga2O3 nanodot structures covered with nanorods on top of their surfaces were obtained at higher molarity, and the densities of nanorods seem to increase with the decrease of pH level. High concentration of Ga3+ and OH- ions may promote the reaction of each other to produce Ga2O3 nanorods in the electrolyte. Such similar nature of Ga2O3 nanorods was also obtained by using hydrothermal process. The grown structures seem to be interesting for application in electronic and optoelectronic devices as well as to be used as a seed structure for subsequent chemical synthesis of GaN by thermal transformation method.

Efficient electrochemical synthesis of pyrido[1,2-a]benzimidazoles

Electrochemical reduction of N-(2-nitroaryl)pyridinium chlorides in alcohol—dilute HCl mixtures gave pyrido[1,2-a]benzimidazoles in high yields in both divided and undivided cells. According to cyclic voltammetry measurements and DFT calculations (B3LYP/6-31+G(d)), the reaction involves intermediate formation of the corresponding hydroxylamine derivative followed by its heterocyclization.