Osmotic coefficients of aqueous sodium carbonate solutions at 25°C

Isopiestic vapor pressure measurements are reported for aqueous sodium carbonate solutions at 25°C using sodium chloride as reference electrolyte. Osmotic and activity coefficients are calculated from the concentrations of the solutions in isopiestic equilibrium. The results are used to calculate the trace activity coefficients of carbonate ion in sodium chloride solutions; these should approximate the trace activity coefficient of carbonate ion in seawater. The solubility of sodium carbonate in water at 25°C has been determined.     

Potentiometric titration of hydroxide,aluminate and carbonate in sodium aluminate solutions

An automated potentiometric titration of hydroxide, aluminate and carbonate in sodium aluminate solutions is described. The addition of barium chloride before titration with hydrochloric acid enables the three components to be determined in one run, involving neutralization of hydroxide, protonation of aluminate and dissolution of barium carbonate. The accuracy and precision of the method are satisfactory for a rapid method used for control of aluminum oxide production.     

Effect of sodium tetraborate (borax) on the thermal properties of frozen aqueous sugar and polyol solutions

The effect of sodium tetraborate (Na(2)B(4)O(7), borax) on the thermal property of frozen aqueous sugar and polyol solutions was studied through thermal analysis. Addition of borax raised the thermal transition temperature (glass transition temperature of maximally freeze-concentrated solutes; T(g)') of frozen sucrose solutions depending on the borax/sucrose concentration ratios. Changes in the T(g)' of frozen mono- and disaccharide solutions suggested various forms of complexes, including those of a borate ion and two saccharide molecules. Borax exerted the maximum effect to raise the oligosaccharide and dextran T(g)'s at borax/saccharide molar ratios of approximately 1-2 (maltose and maltooligosaccharides), 2 (dextran 1060), 5 (dextran 4900), and 10 (dextran 10200). Further addition of borax lowered T(g)'s of the saccharide solutions. Borax also raised T(g) and T(g)' temperatures of frozen aqueous glycerol solutions. The decreased solute mobility in frozen solutions by the borate-polyol complexes suggested higher collapse temperature in the freeze-drying process and improved stability of biological systems in frozen solutions.     

Limited stability of the pH reference material sodium tetraborate decahydrate (“borax”)

Thermogravimetric and X-ray powder diffraction analyses revealed that the pH reference material sodium tetraborate decahydrate (“borax”) is not a stable substance but, loosing some of its water of crystallization, transforms slowly into the pentahydrate. The connected pH changes of the solutions are opposite to and larger than, those expected according to the dilution value of the decahydrate as shown by differential potentiometric measurements. The transformation rate depends on the storing time in the closed original container, the time of and after the first exposure of the material to the atmosphere, the frequency of and the relative humidity during subsequent exposures, and the temperature. The transformation reaction is not understood in detail. However, the experiments showed that sodium tetraborate decahydrate is a reliable pH reference material, whose pH is constant within ΔpH=±0.005 within at least two years after preparation, even if occasionally exposed to the atmosphere. Further work will show whether this time limit can be somewhat extended.     

The determination of hydroxide and carbonate in concentrated sodium chloride solutions

A computer method for the determination of carbonate and hydroxide in concentrated (2.89 M) sodium chloride solutions is described. The method is based on multiparametric curve-fitting and can also be applied to salts of dibasic acids with unknown equilibrium constants. The systematic error is not more than 1%. The titration and calculation takes less than 20 min.     

Kinetics of cleansing action of sodium alkylbenzenesulfonate-sodium carbonate binary solutions

Kinetics of cleansing action of sodium alkylbenzenesulfonate-sodium carbonate binary solutions, as the most widely used components of synthetic detergents, is studied using the procedure based on direct determination of the weight fraction of pollutants removed from the fabric. The effective kinetic parameters of the cleansing process are determined.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1858–1860.Original Russian Text Copyright © 2004 by Kotomin, Naumov, Yakimchuk.     

Phase separation conditions in systems constituted by a nonionogenic surfactant,water, and sodium carbonate

Dependence of the viscosity of aqueous solutions containing a nonionogenic surfactant, OP-10, and sodium carbonate on temperature and concentrations of OP-10 and sodium carbonate was studied. The phase-separation conditions were found for the systems under study.     

Comparative solubilisation of potassium carbonate, sodium bicarbonate and sodium carbonate in hot dimethylformamide: application of cylindrical particle surface-controlled dissolution theory

A surface-controlled dissolution of cylindrical solid particles model is applied to potassium carbonate, sodium bicarbonate and sodium carbonate in dimethylformamide at elevated temperatures. Previously published data for the dissolution of potassium carbonate is interpreted assuming a cylindrical rather than a spherical shape of the particles, the former representing a closer approximation to the true shape of the particles as revealed by scanning electron microscopy. The dissolution kinetics of sodium carbonate and sodium bicarbonate in dimethylformamide at 100 degrees C were investigated via monitoring of the deprotonation of 2-cyanophenol with dissolved solid to form the 2-cyanophenolate anion that was detected with UV-visible spectroscopy. From fitting of experimental results to theory, the dissolution rate constant, k, for the dissolutions of potassium carbonate, sodium bicarbonate and sodium carbonate in dimethylformamide at 100 degrees C were found to have the values of (1.0 +/- 0.1) x 10(-7) mol cm(-2) s(-1), (5.5 +/- 0.3) x 10(-9) mol cm(-2) s(-1) and (9.7 +/- 0.8) x 10(-9) mol cm(-2) s(-1), respectively.     

Aspects on the interaction between sodium carboxymethylcellulose and calcium carbonate and the relationship to specific site adsorption

The mechanisms of adsorption and association for sodium carboxymethylcellulose (NaCMC) in calcium carbonate suspensions have been determined from isothermal calorimetry and adsorption measurements. The equilibrium adsorption isotherms were determined by two different methods of separation; a depletion method and a serum exchange method. The enthalpy of dilution for NaCMC was determined on supernatants obtained from the calcium carbonate suspensions in order to investigate the interaction between NaCMC and dissolved species from the mineral. For comparison, NaCMC was injected into CaCl(2) solutions in order to determine the role of calcium ions in the adsorption process. The initial part of the adsorption isotherm showed a quasi-infinite slope indicating a high affinity for the NaCMC to the calcium carbonate surface, which was significantly reduced when anionic sodium polyacrylate was preadsorbed onto the calcium carbonate implying competitive adsorption. An endothermic enthalpy change was observed between the NaCMC and the calcium carbonate surface, suggesting attachment of the carboxylic acid groups onto the hydrated calcium sites. A similar endothermic enthalpy was observed when NaCMC was injected into CaCl(2) solutions or supernatants obtained from the calcium carbonate suspensions, indicating a complexation of carboxylic acid groups and hydrated calcium ions. It was concluded that the mechanisms of interaction of NaCMC in calcium carbonate suspensions are primarily an association between NaCMC and Lewis acid sites on the calcium carbonate surface and the formation of NaCMC-Ca(2+) complexes in the bulk solution, both of which will be affected by the amount of anionic sodium polyacrylate present.     

Extraction of Cs,Sr, Eu and U in two aqueous phase extraction systems containing sodium carbonate

Extraction systems with two aqueous phases based on concentrated solutions of sodium carbonate and polyoxonium compounds (PEG 3000, Slovafol 910 and 18-crown-6) have been used for the extraction of Cs, Sr and Eu. Besides the variation of PEG and Slovafol, the effect of dicarbollylcobaltate anion, xylenol orange, thymolphthalexone and CDTA on fission product partion has been studied.     

Thermal decomposition of potassium tetraborate tetrahydrate to anhydrous potassium tetraborate in a fluidized bed

Production of anhydrous potassium tetraborate from potassium tetraborate tetrahydrate (PTT) was investigated in a controlled fluidized bed calcinatory (FBC). Single step calcination gives a puffed product with very low bulk density and the calcination of potassium tetraborate tetrahydrate is incomplete since agglomeration starts at temperature higher than 250 °C. Effect of the temperature on the bulk density of the product obtained at the end of single step is given and compared with theoretical calculation. In order to obtain anhydrous potassium tetraborate, dehydration should be carried out at least two stages. The most important step dominating the final bulk density is the first step. Dehydration of potassium tetraborate tetrahydrate up to 85% K₂B₄O₇ content and temperature lower than 150 °C in the first step gives commercial available product at final stage. As a result, both puffed and denser anhydrous potassium tetraborate of 99.5% purity with bulk density around 0.4 and 0.7 g cm⁻³ has been produced by two and three stage calcinations.     

Crystallization of inorganic compounds in polymer solutions. Part I: Control of shape and form of calcium carbonate

Calcium carbonate was precipitated by mixing aqueous solutions of sodium carbonate and calcium nitrate in the presence of water-soluble polymers. When the former was poured into the latter, in which a certain amount of sodium poly(styrenesulfonate) was dissolved, monodisperse spherical crystals were created. The crystal form was vaterite, although, in the absence of the polymer, calcite crystals were obtained in rhombic shape. The factors deciding the shape and form of the crystal were investigated and the role of polymer in the formation of unique crystals was discussed.     

Dielectric properties of propylene carbonate and propylene carbonate solutions

Permittivity data at frequencies from 0.9 to 12 GHz for propylene carbonate and for the solutions of NaI, NaClO₄, Bu₄NI, Bu₄NClO₄, ZnBr₂, and Ca(ClO₄)₂ in propylene carbonate at 25°C are reported and discussed. The contaminating influence of water on the dielectric spectra is shown. Measurements were executed by the method of travelling waves with equipment known to produce data of high precision. Evaluation of the data is performed on the basis of models presupposing one or more relaxation regions. The dielectric spectra of all salts with the exception of ZnBr₂ yield relaxation time distributions with a single critical relaxation time or can be analyzed by assuming two critical relaxation times for the solvent. ZnBr₂ solutions show a supplementary relaxation region at low frequencies which is attributed to the solute. The variation of permittivities at zero frequency with the salt concentration is discussed in the framework of kinetic depolarization. Solvation numbers are estimated.     

Thermal and structural properties of sodium,potassium and carbonate doped strontium hydroxyfluorapatite

Ion-doping in hydroxyapatite bioceramics has attracted a lot of interest particularly for biomedical applications in repairing and replacing failure parts of musculoskeletal systems. Thus the multiple doping aims to mimic and resemble the chemical composition of the bone mineral component. Herein strontium hydroxyapatites bioceramics containing sodium Na⁺ and potassium K⁺ as cationic substituent and carbonate CO₃^2? and fluoride as anionic substituent were synthesized and characterized by several analysis techniques. Therefore the chemical assays indicated that obtained compounds were less stoichiometric comparably to bone tissues. The X-ray diffraction diagrams and the infrared spectra revealed that pure phases of hydroxyfluorapatite containg the cited ions were obtained. The triple insertion of sodium, potassium and carbonate into the apatite structure leaded to the B-type carbonate apatite. The FE-SEM micrographs of the powders were formed by agglomerates. Moreover, the particles' morphology strongly depends on the ions nature and amount. The D-GTA curves indicated that the heating of the powders from the room temperature to 1000 °C didn't affect the structural and thermal stability of the materials apart from a partial decomposition of the apatite inducing the formation of the β-tristrontium phosphate phase and enhancing the biomaterial character of the materials.     

Hydrolysis of polyacrylonitrile in aqueous solution of sodium carbonate

The kinetics of homogeneous hydrolysis of polyacrylonitrile in an aqueous solution of sodium carbonate and the chemical structure of the resulting copolymer are studied by FTIR spectroscopy, ¹³C NMR analysis, and titration methods. It is found that hydrolysis in the presence of sodium carbonate does not include the stage of amidine formation and does not result in the complete exhaustion of nitrile groups in a polymer. The designed partial-hydrolysis method permits the use of polyacrylonitrile for the synthesis of the copolymer with a predominant unit alternation; this copolymer is identical in terms of chemical structure to the Rohacell copolymer obtained through block copolymerization of acrylonitrile and methacrylic acid.     

Recovery of plutonium from carbonate wash solutions

A novel method has been developed for recovery of plutonium and uranium from carbonate wash solutions generated during solvent wash process involved in the reprocessing of high burn up FBTR fuel. The proposed method involves a selective coprecipitation of Pu and U by adding ammonium hydroxide to the pre acidified carbonate wash solution. Substantial removal of DBP by successive steps of coprecipitation, completely eliminates the possibility of undesired solid formation which is mainly due to the presence of high content of DBP. By adopting this method, an excellent decontamination factor for DBP has been achieved without any crud/solid formation. Phosphate content in the final oxide product meets the product specifications. Flowsheet condition necessary for the recovery process for plutonium from the aqueous carbonate solution is formulated and adopted in the CORAL facility.     

Effect of sodium salicylate, sodium oxalate, and sodium chloride on the micellization and adsorption of sodium deoxycholate in aqueous solutions

The salicylate ion increases the rate of bile flow (choleretic effect) and bile salts are known to affect the colonic absorption of oxalate. Owing to this physiological relevance of salicylate and oxalate ions, critical micelle concentration (cmc) values of sodium deoxycholate (NaDC) were determined in aqueous sodium oxalate, sodium salicylate, and sodium chloride solutions by using surface tension, fluorescence, and EMF methods. The results indicate, besides a counterion effect, the influence of coanions on the cmc. In the range from 25 to 40 °C, cmc increases almost linearly with temperature. In the temperature range from 30 to 40 °C, the counterion binding constant β of NaDC micelles has the same value (0.17±0.01) in the presence of sodium chloride and sodium salicylate. On the other hand, in sodium oxalate solution β=0.05±0.02 when oxalate concentration is less than or equal to c* and β=0.48±0.04 above c*, where c*≈0.038 mol kg(-1). EMF measurements also supported this type of counterion binding to NaDC micelles in sodium oxalate solutions. In sodium oxalate solution, at c* a change in the shape of deoxycholate micelles is expected to take place. Salicylate, oxalate, and chloride coanions have a similar effect on the adsorption of NaDC. This study reveals that the choleretic effect of salicylate is not due to the influence of salicylate ions on the micellization of NaDC.     

Electrochemical characteristics of propylene carbonate solutions of tetraethylammonium tetrafluoroborate

The specific and molar electric conductivities of propylene carbonate solutions of Et₄NBF₄ with concentrations of 0.15–1.4 m were determined at 283.15, 298.15, and 313.15 K. The temperature dependence of the electric conductivity of the system was analyzed. The concentration dependence of electric conductivity was described in terms of the Castell-Amis equation. A comparative analysis of the charge transfer in Et₄NBF₄ and LiAsF₆ systems in propylene carbonate was performed using the concept of quasicrystallinity of concentrated electrolyte solutions. The range of potentials in which the electrolyte solutions are stable on a platinum electrode was determined.     

Oxa-Michael addition promoted by the aqueous sodium carbonate

An efficient Michael addition of alcohols to activated alkenes promoted by sodium carbonate with water as reaction medium has been developed. The reaction provides a general, economical and environmentally friendly approach for the synthesis of β-alkoxycarbonyl compounds.     

Effect of barium tetraborate on the separation of tryptic digests of proteins by zone electrophoresis in uncoated capillaries

A simple, fast, efficient and reproducible method for peptide separations in CZE is reported. It consists in running tryptic digests of peptides in an uncoated capillary, in a BGE composed of tetraborate as a buffering ion, in which the typical sodium counterion is substituted with barium. Efficient absorption of this divalent cation to ionized silanols and barium silicate precipitation seem to be able to shield effectively the silica surface from separands. This is demonstrated by the fact that, when tBa(2+) ions are present in solution (from pH 8.5 up to pH 11.0), the electroendoosmotic flow is reversed; such reversal being progressively higher at higher pH values, by up to a four-fold. Separations become progressively better at higher pH values, whereas at pH 11 in sodium tetraborate they are dramatically worsened. It is further hypothesized that the barium silicate layer further protects the silica surface against dissolution and corrosion which is quite substantial at pH 11.