Sodium Hydroxide System Research Articles

Reduction of lead in the lead sulfide-molten sodium hydroxide system

Based on thermodynamic investigations of the reduction of lead from its sulfide compounds using the electron-donating properties of sulfur of its sulfide, we studied the effect of various factors on the reduction of lead (“metallization”) in molten sodium hydroxide. In the range of temperatures of smelting PbS with the alkali (470–510°C), there occurs a “burst” metallization reaching 95% at T = 550°C; at T = 650°C, the process is completed in 15 min; at 650–500°C, the reduction of the metal occurs in the diffusion region. The NaOH: PbS weight ratio (α) exerts a direct effect on the yield of the compact metal (‘lens’). At α = 1.8−0.8, the yield of the compact metal is 96–98%. It has been confirmed experimentally that the chemism of the utilization of elementary sulfur is related to a disproportionation of the latter with the accumulation of S2− and SO42− ions and the possible formation of polysulfide sulfur Sn2−.

Vapor−Liquid Equilibria of Ammonia + Water + Potassium Hydroxide and Ammonia + Water + Sodium Hydroxide Solutions at Temperatures from (293.15 to 353.15) K

Vapor−liquid equilibria of ammonia + water + potassium hydroxide and ammonia + water + sodium hydroxide systems were measured by a static method from (293.15 to 353.15) K. The experimental vapor pressure data have been correlated with temperature and mass percent concentration using an analytical polynomial equation.

Formation of Aluminium Oxide Film on Al Substrate by Micro-Arc-Technology in Electrolytic Solution of Sodium Hydroxide Systems

The objective of this study was to form a polycrystalline oxide film on an Al substrate in electrolytic solutions of sodium phosphate using micro-arc-technology, and to consider a mechanism for the formation of the oxide film by type of sodium phosphate. Micro-arc on the Al substrate did not occur in electrolytic solutions of Na3PO4, Na2HPO4 or NaH2PO4, which were mono-sodium phosphate, preventing micro-arc-processing. However, micro-arc-processing was possible on the Al substrate and crystalline Al2O3 films were formed in electrolytic solutions of Na4P2O7 and Na5P3O10, which were poly phosphoric acid. Micro-arc may not have occurred in the mono-phosphoric acid electrolytic solutions because the resistance value of phosphoric acid radical impurities barrier layer is small in comparison with poly phosphoric acid sodium.

Phase Behavior of Aqueous Two-Phase PEG + NaOH System at Different Temperatures

Phase diagrams and liquid−liquid equilibrium (LLE) data of the poly(ethylene glycol) (PEG) (Mn: 6000) + sodium hydroxide system have been determined at (298.15, 308.15, and 318.15) K. As temperature is increased, this aqueous two-phase system exhibits a phase inversion. Specifically, the PEG-rich phasewhich at low temperatures is the less dense top phasebecomes the lower phase at elevated temperatures. The effect depends on the concentration of both PEG and sodium hydroxide. At the temperatures 308.15 K and 318.15 K, the system shows inversion; and at these temperatures inversion occurs at lower concentrations of either phase-forming constituent. Also, it was found that as temperature is increased the inversion-phase region expands. The osmotic virial equation with temperature-dependent parameters was used to correlate the phase behavior of this system.

Surface properties of aqueous amino acid solutions: I. Surface tension of hydrochloric acid–glycine and glycine–sodium hydroxide systems

The surface tensions of aqueous solutions of four mixtures (hydrochloric acid–glycine hydrochloride, glycine hydrochloride–glycine, glycine–sodium glycinate, and sodium glycinate–sodium hydroxide) were measured as a function of total molality and mole fraction. The measurements correspond to the change in surface tension with variation of pH. The contribution of glycine hydrochloride to the increments in surface tension is equivalent to that observed for the aqueous solution of glycine, while the contribution of sodium glycinate is much larger than that of glycine. The variations in surface tension on mixing in the surface region are discussed using comparisons with mixtures of simple salts.

Effect of high pressure on isomerization and degradation of lactose in alkaline media.

The combined effects of temperature (60 degrees C) and high-pressure treatments (400 MPa for 3 h) on the isomerization-degradation of lactose (10%) in basic media were studied. The formation of isomeric disaccharides (lactulose and epilactose) and galactose decreased by the application of high pressure in aqueous sodium hydroxide 4 mM (pH 10.2) and 8 mM (pH 10.6), and sodium carbonate-bicarbonate buffer (pH 10.0). In addition, no substantial color development was observed in the sodium hydroxide systems for high and atmospheric pressure, whereas the application of high pressure led to a noticeable decrease of color development in the carbonate-bicarbonate system.

A thermodynamic study of the aqueous (sodium chloride + sodium hydroxide) electrolyte using sodium amalgam and thallous chloride electrode cells

The aqueous mixed (sodium chloride + sodium hydroxide) system has been studied using e.m.f. measurements at T=298.15 K of the combined cells Pt|Na–Hg|NaCl( m 1)+NaOH( m 2)|HgO|Hg|Pt and Pt|Tl–Hg|TlCl|NaCl( m 1)+NaOH( m 2)|HgO|Hg|Pt at constant total molalities ( m 1+ m 2) of (1, 2, 3, 4, 5, 6, 7, 9, and 11) mol·kg −1. The mean molal activity coefficients γ of each single component have been determined as a function of the respective molalities. For both components, the behaviour can, with reasonable approximation, be represented by Harned’s rule (linear dependence of lgγ on m), although a quadratic dependence is more appropriate. In terms of the mixing fraction X= m 2/ m TOT, the lgγ against X curves for NaCl and NaOH have slopes in opposite directions, contrary to (KCl+KOH) aq and most other (MX+MY) aq. The respective trace activity coefficients are unequal, and both of them are lower than the corresponding pure-component activity coefficients.

Selective Hydrolysis of Nitriles to Amides Using NaOH-PEG Under Microwave Irradiation

We describe here an efficient, rapid and selective method for the conversion of nitriles in to their corresponding amides in the presence of PEG-400, aqueous sodium hydroxide system under microwave irradiation.

Indirect electrochemical oxidation of aliphatic ketones mediated by the NaI–NaOH system:a facile way to unsaturated conjugated esters

Indirect electrochemical oxidation of aliphatic ketones in methanol in an undivided cell in the presence of sodium iodide–sodium hydroxide system leads to the corresponding unsaturated esters as a result of the electrochemically induced Favorskii rearrangement of the primarily formed α , α -diiodoketones.

New fibres prepared from cellulose-aqueous solution of sodium hydroxide systems (review)

The following basic conclusions were drawn from the published data examined; cellulose treated in steamblast conditions can form solutions and gelling pastes in an aqueous solution of sodium hydroxide; the solubility of cellulose in aqueous sodium hydroxide solution is primarily a function of the intramolecular bonds in the cellobiose unit with constant DP; intramolecular bonds are most efficiently broken in steamblast treatment in the cellobiose unit of cellulose I and cellulose III; monofilaments and yarns were obtained from solutions and gelling pastes of cellulose in aqueous sodium hydroxide solution; the physicomechanical properties of the monofilaments and yarns obtained from solutions and gelling pastes of cellulose in aqueous sodium hydroxide solution are still significantly lower than these indexes for viscose textile yarn.

Structure and Morphology of Cellulose Films Coagulated from Novel Cellulose/Aqueous Sodium Hydroxide Solutions by Using Aqueous Sulfuric Acid with Various Concentrations

Structure and morphology of the cellulose films coagulated from novel cellulose/9 wt% aqueous (aq.) sodium hydroxide (NaOH) systems (polymer concentration CP≤5.6 wt%) by using aq. sulfuric acid (H2SO4) with various concentration (Csa=20—80 wt%) as coagulants were investigated. For this purpose two types of alkali-soluble celluloses with either crystal form of cellulose-I (Cell-I; steam exploded spruce pulp) or cellulose-II (Cell-II; regenerated from cotton/cuprammonium solution) were utilized. SEM observation on the lyophilized coagulated cellulose films revealed that all the films have basically porous structure more or less, constituted by collision of secondary particles. Coagulation from two types of cellulose solutions underwent in a quite different way as a function of Csa of coagulant: (1) For alkali-soluble Cell-II system, the existence of secondary particles was evident in the range of Csa≥20 wt% and the most dense structure was given when Csa=60—65 wt%, (2) For alkali-soluble Cell-I system, the secondary particles became detectable at Csa≥40 wt% and the coagulant with Csa=70 wt% gave the most dense structure of the film, and (3) the size of particles constituting the most dense films is smaller for Cell-II system than Cell-I system. The coagulant with Csa≥60 wt% proved to act as strong dehydrant from cellulose solutions by Raman spectroscopy and the neutralization rate of Cell-II system was much higher than Cell-I system. CP/MAS 13C NMR analysis showed that both densely coagulated films developed practically no intramolecular hydrogen bond at C3 position.

Strong acid equivalent control of pH processes: an experimental study

The control of pH is widely recognized as a difficult problem. The Strong Acid Equivalent approach for control of pH processes consists of defining an alternate equivalent control objetive, the Strong Acid Equivalent, which is linear in the states and using a linear control law in terms of this new control objective. The Strong Acid Equivalent is then calculated on line from pH measurements given a nominal titration curve of the inlet stream. A laboratory system has been built to implement this method. Experimental results for the hydrochloric acid / sodium hydroxide and acetic acid / sodium hydroxide systems are given. The results show the control which can be achieved with the Strong Acid Equivalent method.

The Electro‐oxidation of Some Insoluble Inorganic Sulfides, Selenides, and Tellurides in Cationic Surfactant‐Aqueous Sodium Hydroxide Systems

A study was made of the electro‐oxidation of several sulfides, selenides, and tellurides in cationic surfactant‐aqueous sodium hydroxide suspensions in a slurry cell and a sandwich cell. Because the cationic surfactant increased the oxidation potential of water, it was possible to observe and study separate voltammetric waves for the oxidation of the sulfides to sulfur, sulfite, and sulfate; the selenides to selenium, selenites, and selenates; and the tellurides to tellurium, tellurite, and tellurate. Superimposed, in some cases, on these oxidation waves were waves for the oxidation of the metal ions to higher oxidation states. Controlled potential coulometric studies of these oxidations showed that it was possible to perform each of these oxidations with essentially 100% current efficiency. The oxidation potentials of the sulfides to sulfur reflected differences which could be attributed to differences in crystallization energies. In cases where the oxidation of the metal ion did not interfere, the potentials for oxidation of sulfur to sulfite and sulfite to sulfate were independent of the metal ion because these reactions were the same. In a similar manner, the oxidation of the selenium to selenite, selenite to selenate, tellurium to tellurite, and tellurite to tellurate all showed potentials that were independent of the metal ion that was present. The oxidation of the selenides to selenium and tellurides to tellurium all occurred at the same potential and this potential was, within experimental error, equal to the first oxidation peak potential for the surfactant. This led to the conclusion that these oxidations all proceeded by a mechanism that involved electrochemical oxidation of the surfactant followed by chemical oxidation of the solid.

Dielectric relaxation studies of ion motions in electrolyte-containing perfluorosulfonate ionomers. 1. Sodium hydroxide and sodium chloride systems

Dielectric relaxation studies of ion motions in electrolyte-containing perfluorosulfonate ionomers. 1. Sodium hydroxide and sodium chloride systems

Synthesis of metal‐containing carbohydrate polymers employing crown ether phase transfer catalyzed interfacial condensation

AbstractPhase transfer catalyzed interfacial reaction of the polysaccharide dextran (C6H10O5)n with organotitanium and organotin dichlorides to form metal‐containing carbohydrate polymers has been carried out in the presence of two bases, sodium hydroxide and triethylamine. Interfacial systems employing sodium hydroxide with a crown ether phase transfer catalyst (PTC) gave generally greater yields compared with the analogous systems without a PTC. The trend of maximum yield for triethylamine systems with organotin dichloride not containing a PTC was different from that observed for the sodium hydroxide systems without a PTC, probably because of the ability of triethylamine to act as a PTC.

The thermal decomposition of HCOONa in presence of NaOH

Abstract The run of the thermal decomposition of sodium formate in sodium formate - sodium hydroxide system has been examined thermoanalytically. It has been found that sodium hydroxide being the reagent quantitatively reacting with sodium formate, keeps as the catalyst of the reaction of the thermal decomposition of sodium formate to sodium oxalate and that the selectivity of its catalytic action decreases if the concentration of oxygen in the atmosphere increases. The solid products of the thermal decomposition of sodium formate there are sodium carbonate and sodium oxalate: As the last-mentioned product usually is the desirable one the selectivity related to sodium oxalate is the well-founded characterization of the process where nf2 is the number of sodium formate moles reacting according to the reaction (2), nof is the initial (and urder nonisothermal conditions also total) number of solium formate moles. Let's characterize the composition of the mixture of sodium hydroxide and sodium formate by

Phase Transfer Catalyzed Polycondensation of α, α′-Dichloro-p-xylene with 2,2-Bis(4-hydroxyphenyl)propane II. Some Aspects of Phase Transfer Catalyzed Polycondensation Reaction in the Tetrahydrofuran-Dimethyl Sulfoxide/ Aqueous Sodium Hydroxide System

Phase transfer catalyzed (PTC) polycondensations of α, α′-dichloro-p-xylene with 2,2-bis(4-hydroxyphenyl)propane were carried out in a THF–DMSO (3: 1)/aqueous sodium hydroxide system at 60°C in the presence of quaternary ammonium halides. For both tetra-n-butylammonium bromide and hexadecylammonium bromide, the following rate equation was obtained: polymerization rate=k[Q+X−]0.57[NaOH]2.3 where [Q+X−] and [NaOH] stand for the concentrations of a phase transfer catalyst in an organic layer and sodium hydroxide in an aqueous layer, respectively. The catalytic activity for the PTC polycondensation was in the increasing order of (CH3)4NBr<(C2H5)4NBr<C6H13(CH3)3NBr<C8H17(CH3)3NBr<C10H21(CH3)3NBr ≍ C12H25(CH3)3NBr ≍ C14H29(CH3)3NBr<C16H33(CH3)3NBr<(C3H7)4NBr<(C4H9)4NBr< (C5H11)4NBr. The counter halide anions for benzyltriethylammonium cation also affected the polycondensation rate, which decreased in the order of chloride > bromide > iodide. The addition of sodium chloride to the PTC polycondensation system in the presence of benzyltriethylammonium chloride caused little change in the polymerization rate but always gave a white, soluble polyether even when some drastic reaction conditions were applied.

The mechanism of cellulose alkalization in the isopropyl alcohol–water–sodium hydroxide–cellulose system

AbstractThe mechanism of cellulose alkalization in isopropyl alcohol (IPA)–water–sodium hydroxide system was studied from the viewpoint of the selective distribution of sodium hydroxide between cellulose and the medium, and of the lattice transition of cellulose. A mixture of IPA, water, and sodium hydroxide spontaneously separates into two layers, i.e., the upper layer solution (ULS) consists of IPA, water, and a small amount of sodium hydroxide and the lower one (LLS) consists of sodium hydroxide, water, and a very small quantity of IPA. The role of the ULS and the LLS was distinctive. The ULS has a function to distribute sodium hydroxide with water in cellulose uniformly according to the distribution equilibrium between ULS and cellulose, and the ULS recovers sodium hydroxide with water from the LLS as the distribution equilibrium shifts in the alkalization of cellulose. The concentration of sodium hydroxide in the LLS and that of IPA in the ULS exerts an influence on the lattice structure of alkali cellulose. During the transformation from cellulose I to alkali cellulose, decrystallization does not occur. Some portion of alkali cellulose reverted to cellulose I by regeneration.

Degradation rate and chemical composition of different types of alkali‐treated straws during rumen digestion

AbstractThe degradation in the rumen and change in chemical composition of untreated and four samples of alkali‐treated barley straw were studied in farm‐scale treatments with ammonia, ‘dry’ sodium hydroxide and two different aqueous sodium hydroxide systems. The alkali treatments increased the fraction soluble in organic solvents and decreased the lignin content (determined as Klason lignin). The amounts of cellulose and arabinoxylans were not significantly changed. The degree of rumen degradability increased with the order of alkaline treatment given above. The degradation rates of dry matter and the NDF fraction were parallel to each other but varied considerably with the treatments. The two most efficient aqueous alkaline treatments showed a degradation rate four times that of untreated straw. For these two samples the arabinoxylans were solubilised faster than cellulose during the first part of the incubation. In the other samples the degradation of arabinoxylans and cellulose ran almost parallel. During the rumen incubation the lignin content of the straw residues increased for all samples. There was an inverse relationship between the content of p‐coumaric and ferulic acids on the degree of digestibility. A relationship between acetyl groups and digestibility was not found.

Phase-Transfer Catalyzed Polycondensation of α,α′-Dichloro-p-xylene with 2,2-Bis(4-hydroxyphenyl)propane

The phase-transfer catalyzed polycondensation of α,α′-dichloro-p-xylene with 2,2-bis(4-hydroxyphenyl)propane was carried out in the presence of benzyltriethylammonium chloride in a two-phase system of an aqueous alkaline solution and its solution-immiscible organic solvents such as benzene, tetrahydrofuran (THF), and N-methyl-2-pyrrolidone. Addition of dimethyl sulfoxide (DMSO) to the system not only enhanced the reaction but also suppressed side reactions to give a completely soluble, high molecular weight polyether. Optimal solvent systems at 60°C were THF–DMSO (3: 1)/ or nitrobenzene–DMSO (3: 1)/50 wt% aqueous sodium hydroxide, which gave the polymer having an inherent viscosity of 0.54 dlg−1. The reaction temperature also affected the inherent viscosity of the resulting polymer causing it to become 0.62 dlg−1 at 100°C in a toluene–DMSO (3:1)/50wt% aqueous sodium hydroxide system.