Aqueous Ammonium Sulfate Research Articles

Dissociation Constants of Ammonium Ion and Activity Coefficients of Ammonia in Aqueous Ammonium Sulfate Solutions

Dissociation constants of NH4+ ion, Ka,c = cH+(T)cNH3/cNH4+, where c denotes molarity and cH+(T) = cH+ + cHSO4-, were determined at 298.15 K in aqueous (NH4)2SO4 solutions at different ionic strengths (I = 0.75−7.5 mol dm-3) by potentiometry using a glass electrode. The Ka,c values were converted to those on the molality basis by use of the densities of the corresponding solutions. The activity coefficients of ammonia, γc,NH3 and γm,NH3, respectively, on the molar and molal bases, were determined by a transpiration method. The observed dissociation constants on the molality basis, pKa,m, were compared with those calculated from the Pitzer equations.

Reaction Probabilities for N2O5 Hydrolysis on Sulfuric Acid and Ammonium Sulfate Aerosols at Room Temperature

The uptake coefficients for N2O5 hydrolysis have been measured at room temperature on micron-sized aerosols composed of both sulfuric acid aqueous solutions and ammonium sulfate solutions. The measurements have been performed in a laminar flow tube which is coupled to a chemical ionization mass spectrometer for monitoring the concentration of N2O5 in the gas phase and an optical particle counter which sizes the aerosols and determines their number density. The aerosols are generated with an ultrasonic nebulizer from aqueous solutions of either sulfuric acid or ammonium sulfate, and their liquid-phase concentration is determined by the relative humidity (RH) set within the flow tube. For both the sulfuric acid and ammonium sulfate aerosols, the reaction probability (γ) is largest for the lowest relative humidities studied: for sulfuric acid aerosols, γ = 0.05−0.06 for RH = 9−20%, γ = 0.02 for RH = 90%; for ammonium sulfate aerosols, γ = 0.04−0.05 for RH = 50−69%, γ = 0.02 for RH = 83−94%. In the case of a...

Hypoglycaemic Effects of Opuntia ficusindica Mill., Opuntia lindheimeri Engelm and Opuntia robusta Wendl. in Streptozotocin‐induced Diabetic Rats

The hypoglycaemic activities of Opuntia ficus-indica, O. lindheimeri and O. robusta were investigated in streptozotocin-induced diabetic rats using enteral (oral) and parenteral (intraperitoneal and intravenous) routes of administration. When the aqueous extracts of the three Opuntia species were administred intraveneously, they produced a hypoglycaemic effect. However, when the extracts were administered orally, only O. lindheimeri produced a hypoglycaemic effect. A dilute aqueous (ammonium sulphate) solution of O. lindheimeri dialysate also produced a hypoglycaemic effect when administered intravenously. Intraperitoneal administations of all Opuntia species extracts including O. lindheimeri dialysate failed to produce hypoglycaemic effects. It appears that the concentration and/or potency of the active hypoglycaemic principle in Opuntia cacti is species-specific.

Hypoglycaemic Effects ofOpuntia ficus-indica Mill.,Opuntia lindheimeri Engelm andOpuntia robusta Wendl. in Streptozotocin-induced Diabetic Rats

The hypoglycaemic activities of Opuntia ficus-indica, O. lindheimeri and O. robusta were investigated in streptozotocin-induced diabetic rats using enteral (oral) and parenteral (intraperitoneal and intravenous) routes of administration. When the aqueous extracts of the three Opuntia species were administred intraveneously, they produced a hypoglycaemic effect. However, when the extracts were administered orally, only O. lindheimeri produced a hypoglycaemic effect. A dilute aqueous (ammonium sulphate) solution of O. lindheimeri dialysate also produced a hypoglycaemic effect when administered intravenously. Intraperitoneal administations of all Opuntia species extracts including O. lindheimeri dialysate failed to produce hypoglycaemic effects. It appears that the concentration and/or potency of the active hypoglycaemic principle in Opuntia cacti is species-specific.

Linear interdependence ofR M pair values of substances in salting-out planar chromatography

It has been established that in salting-out planar chromatography there is a linear dependence between the pair ofRM values of substances obtained on one or two sorbents using the same series of aqueous ammonium sulphate solutions (RM pair linearity rule). In addition, the proportionality between the distance of the individual points on the regression straight line and the difference in mol% of the salt in the corresponding solvents has been established (proportionality rule).

Solubility of Ovalbumin in Ammonium Sulfate Solutions

The solubilities of the protein ovalbumin in aqueous ammonium sulfate solutions ranging from 18 to 30 g ammonium sulfate/100 g water at 30 °C were determined for pH values in the range 4.58-5.4. A correlation of the data is presented which is estimated to predict solubilities within ±5%.

Thermodynamic Properties of Aqueous (NH4)2SO4 to High Supersaturation as a Function of Temperature

Ammonium sulfate is an important component of aqueous atmospheric aerosols in both remote and urban regions. Equilibrium water vapor pressures over supersaturated aqueous ammonium sulfate have been determined from 278.15 to 313.15 K using an electrodynamic balance. Partial molar enthalpies of water (L{sub 1} to {approximately}25 mol/kg) and partial molar heat capacities (J{sub 1}, to {approximately}8 mol/kg) have been calculated from the measurements, together with enthalpies of solution, heat capacities, and boiling point elevations. The results have been used to parameterize a mole-fraction-based activity coefficient model. Equilibrium constants for the reaction (NH{sub 4}){sub 2}SO{sub 4}{sub (cr)} {l_reversible} 2NH{sub 4}{sup +} (aq) + SO{sub 4}{sup 2{minus}} aq have been evaluated from 373.15 K to the eutectic point (5.00 mol/kg, 254.21 K). The model satisfactorily represent water vapor pressures and saturations with respect to solid phases ice and ammonium sulfate from 253 to 373.15K and up to 8--10 mol/kg, and water vapor pressures from 278.15 to 313.15 K and up to {approximately}25 mol/kg.

Growth of monodisperse, submicron aerosol particles exposed to SO2, H2O2, and NH3

The growth of monodisperse particles (0.07 to 0.5 µm) exposed to SO2 (0–860 ppb), H2O2 (0–150 ppb) and sometimes NH3 (0–550 ppb) in purified air at 22 °C at relative humidities ranging from 25 to 75% were measured using the Tandem Differential Mobility Analyzer technique. The experiments were performed in a flow reactor with aqueous (NH4)2SO4 and Na2SO4 droplets. For (NH4)2SO4 droplets the fractional diameter growth was independent of size above 0.3 µm but decreased with decreasing size below that. When NH3 was added the fractional growth increased with decreasing size. Measurements were compared with predictions of a model that accounts for solubility of the reactive gases, the liquid phase oxidation of SO2 by H2O2, and ionic equilibria. Agreement between measured and predicted droplet growth is reasonable when the ionic strength effects are included. Theory and experiments suggest that NH3 evaporation is responsible for the decrease in relative growth rates for small aqueous ammonium sulfate particles. The observed droplet growth rates are too slow to explain observed growth rates of secondary atmospheric sulfate particles.

Solvent Swelling Studies of Green River Kerogen

Kerogen has been isolated from Green River oil shale by dissolving the minerals in HF and HCI and also by using aqueous ammonium sulfate. The resulting kerogen samples were swollen in 28 different solvents. The volumetric solvent swelling of the kerogen roughly follows the predictions of regular solution theory for almost all of the solvents including good hydrogen bond acceptors. The solubility parameter from the swelling studies is close to that calculated from Siskin's structure. Hydrogen bonding does not seem to be an important factor because good hydrogen bonders show swellings similar to non-hydrogen bonders of similar solubility parameter. The inorganic content of the isolated kerogen does not have a large effect on solvent swelling. Samples containing 42% inorganics generally swell somewhat more than samples containing 5% inorganics. The cross-link density of this kerogen is high.

Salting-out thin-layer chromatography of transition metal complexes. III: Investigation of the behaviour of mixed aminocarboxylato cobalt(III) complexes on cellulose

Salting-out thin-layer chromatography of fourteen mixed aminocarboxylato cobalt(III) complexes (three homologous series) on cellulose has been investigated with eight aqueous ammonium sulphate solutions. A pronounced salting-out effect, with reversed-phase order, was observed with bis(aminocarboxylato) complexes, whereas with mono(aminocarboxylato) complexes such a behaviour was noticeable only at higher salt concentrations. In both cases a positive linear dependence between the RM values of the complexes and mol % of the salt in the solvent system, and between the RM values and the number of carbon atoms in the hydrocarbon part of the complexes belonging to the same homologous series, were found. These phenomena were explained by the mechanism of non-specific hydrophobic interactions.

Purifying phosphogypsum for cement manufacture

Phosphogypsum available as a by-product from the wet process phosphoric acid industry in India contains various impurities which, when used in cement manufacture, impair the strength of the cement. Such methods as simple washing with water or wet sieving of phosphogypsum, heating to hemihydrate-anhydrite stage followed by washing or neutralization with lime, and treating phosphogypsum with a mixture of sulphuric acid and silica or hot aqueous ammonium sulphate solutions have been suggested for reducing the amount of impurities or making them ineffective. In the investigation reported here, treatment of phosphogypsum with aqueous ammonium hydroxide solutions was tried to purify phosphogypsum and render it suitable for cement manufacture. The treatment converts phosphatic and fluoride impurities into water-soluble ammoniated compounds which can be removed with a stream of water. The results of chemical and physical tests and differential thermal analysis of the phosphogypsum with and without the ammonium hydroxide treatment confirmed the efficacy of the treatment for purifying phosphogypsum. The treated phosphogypsum was found to have comparatively smaller amounts of impurities that the untreated material. The cement produced was found to have strength characteristics similar to those produced using mineral gypsum.

Salting-out thin-layer chromatography of transition metal complexes: II. Mixed aminocarboxylatocobalt(III) complexes on a polyacrylonitrile sorbent

Fourteen mixed aminocarboxylatocobalt(III) complexes, belonging to three homologous series, were investigated by salting-out thin-layer chromatography on a polyacrylonitrile sorbent using six aqueous ammonium sulphate solutions. An increase in the salt concentration of the solvent system was found to result in a decrease in the R F values of the complexes, giving rise to a reversed-phase order. It was established that the members of a homologous series containing aminocarboxylato ligands with a straight carbon chain exhibit lower R F values than the isomeric members with branched chains. A linear dependence was found between the R M values of the complexes belonging to the same homologous series and the number of carbon atoms in their hydrophobic parts. An increase in the salt content of the solvent system causes an increase in the separation factor (α) between two adjacent members of a homologous series, and a linear dependence between log α and the concentration of ammonium sulphate was established. The separation processes described are consistent with a mechanism of non-specific hydrophobic interactions.

The effect of clay on gypsum filterability in the nitrophosphate process

The influence of clay added to Khouribga phosphate rock during the dissolution with nitric acid in the nitrophosphate process, upon the filterability of gypsum (calcium sulphate dihydrate) was studied. The precipitation of the acidulate with an aqueous ammonium sulphate containing solution was investigated in a continuously operated bench scale reactor system. It was found that the filtration time of a gypsum-crystals-containing filter cake with a height of 50 mm could be reduced by up to a factor of 5 by adding approximately 0.5 percent by weight clay in relation to the amount of phosphate ore. Based on our experiments we can calculate that the addition of clay in the range 0.4–3 percent by weight to the phosphate ore can increase the production capacity of a rotary tilting-pan filter system for separation of the gypsum from the mother liquor by more than a factor of two. Moreover because in this range of clay concentrations the capacity becomes almost constant we may conclude that for this system the production capacity is relatively insensitive to fluctuations in the clay dosage system.

A High-Performance Liquid Chromatography Study of D-Cellobiose Degradation Under Fenton Conditions

Abstract Cellobiose was used to model chemical processes taking place during the weathering of cotton fiber cellulose. High-performance liquid chromatography (HPLC) showed that the products of cellobiose degradation were D-glucose and organic acids under Fenton-type conditions (ferrous ion plus H202). Hydrogen peroxide was added directly or photochemically generated in situ by the action of UV light upon aqueous ferrous ammonium sulfate. Effects on D-cellobiose degradation caused by added peroxide or ferrous ion were nonitored at varying concentrations and under UV light and dark conditions. Increasing concentrations of peroxide or ferrous ion resulted in greater degradation. Samples exposed to UV light (350 nm) experienced greater degradation than those not exposed.

Studies on photoisomerization of 4,4′-diaminostilbene-2,2′-disulphonic acid for quality assurance by high-performance liquid chromatography

Studies on the photoisomerization of 4,4′-diaminostilbene-2,2′-disulphonic acid (DAST) were carried out using controlled light at 350 nm to follow the E to Z isomerization and to develop a simple and rapid stability-indicating assay using high-performance liquid chromatography. Photoisomers and process impurities, viz., 4,4′-diaminodibenzyl-2,2′-disulphonic acid and 4,4′-dinitrostilbene-2,2′-disulphonic acid, were separated using a reversed-phase C 18 column, an eluent containing aqueous ammonium sulphate and 2-propanol and a variable-wavelength UV spectrophotometric detector at 245 and 338 nm. The method was used for quality assurance and validated using several lots of industrial samples. The mean recovery of DAST from authentic samples was 99.75 ± 1.17%.

Binary mutual diffusion coefficients of aqueous ammonium and potassium sulfates at 25°C

The diffusion coefficients of aqueous ammonium and potassium ions at infinite dilution differ by only 0.01% at 25°C, so, according to Nernst's law, the binary mutual diffusion coefficients D of pairs of dilute aqueous ammonium and potassium salts should be nearly identical. Yet precise optical interferometric data for ammonium and potassium sulfates contradict this rule: the value of D reported previously for 0.05 mol-L−1 aqueous ammonium sulfate is 0.80×10−5 cm2-s−1, while the corresponding value for potassium sulfate is 1.24×10−5 cm2-s−1 about 50% higher. To confirm this surprising result, the diffusion coefficients of the two salts have been measured by the Taylor dispersion technique. The diffusion coefficients of the salts are indeed nearly identical, and the earlier ammonium sulfate data are found to be incorrect.

Solvent evaporation rates in the closed capillary vapor diffusion method of protein crystal growth

The rate of transport of water vapor from the evaporator end to the condenser end through the intervening air space in closed protein crystal growth capillaries of the Plaas-Link design has been analyzed both theoretically and experimentally. The theory is based upon the assumptions that (1) the concentration of the precipitating agent exceeds that of all other solutes and (2) the process determining the rate of approach to equilibrium is the diffusion of water vapor through the air space. According to the theory, the rate of equilibrium depends upon ten parameters. These include the absolute temperature, the vapor pressure of pure water, the vapor pressure lowering coefficient of the precipitating agent, the diffusion coefficient of water vapor through air, the length of the air space, the cross sectional area of the capillary, the total numbers of moles of water and of precipitant, and also their differences at the beginning of the experiment. Equilibration data taken with aqueous ammonium sulfate in tubes oriented with the evaporation flux both parallel and antiparallel the ambient gravity are essentially identical and in quantitative agreement with the theory.

Effects of baking on water-soluble non-starch polysaccharides in white bread fractions

Water-soluble non-starch polysaccharides were extracted from white flour and dough as well as from crumb, inner crust and outer crust fractions of white bread, baked at 210 °C for 22 or 35 min. Results from the two baking experiments were very similar. Extracted polysaccharides were fractionated on DEAE-cellulose and by different solubility properties in aqueous saturated ammonium sulfate. Fractions isolated were characterized by sugar- and 1H-n.m.r. analysis, revealing the presence of arabinoxylan mixtures with widely different degrees of arabinose substitution. Arabinogalactanproteins isolated showed little variation in galactose/arabinose ratio (1·5–1·8). Highfield 1H-n.m.r, of arabinoxylan fractions was particularly useful for estimating the ratios of terminal arabinofuranosidic residues linked to xylose residues at O-2 and O-3 or solely at O-3.

Corrosion of aluminized low-carbon steel exhaust system in vehicles equipped with three-way catalytic converters and development of a protective polymeric coating

In automobiles equipped with three-way catalytic converters (TWCCs) with no secondary air, the cause of corrosion of the exhaust system has been identified to beammonium sulfate formation. Ammonia is formed over three-way catalysts (TWCs) under reducing conditions and reacts with sulfur trioxide, formed during lean conditions and stored on high surface area Al{sub 2}O{sub 3}, to form ammonium sulfate. The condensate solution of ammonium sulfate thus formed in the exhaust system reacts with the aluminized surface of the aluminized low-carbon steel, stripping it away and corroding the low carbon steel components. A coating composition has been developed from a new phenolic-type epoxy resin and diaminodiphenyl sulfone. This coating has a softening temperature higher than 200{degrees}C and is thermally stable in air up to 375{degrees}C. The coating adheres well to aluminized low-carbon steel and provides excellent corrosion protection during aqueous ammonium sulfate exposure in bench tests and during aging in a stimulated exhaust for 15000 simulated miles. Field testing of this polymer-coated exhaust system is planned on prototype vehicles.

Distribution equilibria in the adsorption of cobalt(II) and nickel(II) on Levextrel resin containing Cyanex 272

Equilibrium distributions of cobalt(II) and nickel(II) were measured in the adsorption on Levextrel resin containing Cyanex 272 as extractant from aqueous ammonium nitrate and sulfate solutions. It was inferred that the extractant in the resin behaves in the same manner as in the solvent extraction. The distribution data were analyzed quantitatively by taking account of the extraction reaction described below to evaluate the apparent equilibrium constants of the extraction reactions for each metal and each aqueous medium as well as the apparent stability constants of cobalt(II)- and nickel(II)-amine complexes. M 2++(2+x) H 2 R 2 ⇌ MR 2·(2+2x) HR +2 h + where x=0 for cobalt(II) and x=1 for nickel(II). Cobalt(II) is more selectively adsorbed over nickel(II) from sulfate media than from nitrate media though the adsorption itself is suppressed by sulfate anion owing to the formation of metal-sulfato complexes.