Extraction of palladium from nitric acid medium and its spectrophotometric determination using arsenazo III

Summary Di-octyl sulphoxide in xylene was successfully employed for extracting palladium from 0.5 to 1.5 mol/l nitric acid medium. The extracted species was found to be Pd(NO₃)₂·2DOSO. The palladium was back extracted into a mixture of 2 mol/l sodium carbonate and 0.05 mol/l ammonia. The recovery was found to be quantitative. A spectrophotometric method using Arsenazo III was developed in nitric acid medium for the determination of palladium. The colour development was found to be maximum in the acid range of 2.5 to 5 mol/l. Beer's law was found to be obeyed in 1 to 100 g range of palladium. The molar extinction coefficient was found to be 2.26×10⁴ l/mol/cm. The RSD obtained at 16 g of palladium was 5%.     

Kinetics of oxidation of some amino acids by KMNO4 in a moderately concentrated H2SO4 medium in the presence and absence of Ag+

The kinetics of oxidation of glycine, alanine, phenylalanine, serine threonine, aspartic, and glutamic acid by acid permanganate were investigated to elucidate the mechanism of the reactions. The rate law was found to be The reactions were found to be acid catalyzed, and the kinetic data indicate the participation of the water molecules in the rate-determining step as a proton-abstracting agent from the substrate, as per Bunnett's hypothesis. As Ag⁺ was found to catalyze these reactions, the oxidation of glycine and glutamic acid was studied, and the rate law was found to be A probable mechanism consistent with the observed results is discussed.     

Estimation and Comparison of Pore Charge on Titania and Zirconia Membranes Prepared by Sol-Gel Route Using Zeta Potential Measurement

An attempt has been made to synthesize ceramic titania and zirconia membranes by sol-gel process by filtering respective viscous colloidal sol through microporous alumina support and gelling followed by sintering at 400°C and 470°C respectively. The static charge on the pores of the so formed membranes and the pore size distribution determine the applicability in filtering colloidal solution. The mean pore size from SEM were found to be 0.65 m and 0.54 m for titania and zirconia membranes respectively with 1.47 × 10⁷/cm² as pore density for both. The filtration characteristics during membrane layer formation showed that the membrane layer formation started after 35 minutes in the case of titania membrane and 40 minutes in the case of zirconia membrane. From the gravimetric estimation of water content of the membranes the thickness of the membrane was found out to be 3 m and the porosity was found out to be 0.30 for both the cases. The particle charge density was estimated from the zeta potential and the particle size. The pore charge density was estimated from the particle charge density, pore density, pore diameter and the thickness of the membrane layer. The membrane pore charge density was found to vary between 3 to –1 Coulombs/cm² in the case of titania membrane and 7 to –0.5 Coulombs/cm² in the case of zirconia membrane in the pH range 1–12.     

Solvent extraction of Re/VII/ with methylene blue into nitrobenzene

A method has been developed for the extraction of rhenium/VII/ with methylene blue. Nitrobenzene was found to be the most effective extractant for Re/VII/. The stoichiometry of metal to reagent determined by the method of substoichiometric extraction and slope-ratio method was found to be 11.     

Effect of high pressure on the rate constant of the Diels-Alder reaction between furan and maleic anhydride

The effect of high pressure (up to 700 MPa) on the rate of the Diels-Alder reaction between furan and maleic anhydride has been investigated in deuterated acetone at 20C. The volume effect of the reaction at atmospheric pressure is found to be V₀=–28.0 cm³/mole. The rate constants for the formation, decomposition and isomerization of the products have been found by numerical integration. The volume of activation V in the pressure range studied has been determined from the observed dependence of log k upon P by spline approximation and was found to be –30.5 cm³/mole at atmospheric pressure, close to the volume change in the reaction, which is consistent with the assumption of a conjugated cyclic transition state.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 525–529, March, 1990.     

Measurement of concentration of calcium-45 in aqueous solutions with a silicon photodiode as a beta-ray detector

It was found that a commercial silicon photodiode modified only by removing its window can be used as a low-background detector of -rays from⁴⁵Ca solutions. We built a test system which could count -rays from 0.21% hot CaCl₂ solutions in the concentration range of 10^–5–10^–8M with linear sensitivity. Such a system using a small photodiode for real-time detection of -rays from small amounts of assay solutions could have many applications in the field of biophysics, biochemistry and physiology, e.g., in the study of Ca-binding proteins. This photodiode was also found to be suitable for measurement of low-energy -rays from¹⁴C.     

The application of the pitzer equations to 1-1 electrolytes in mixed solvents

Pitzer's equation for the activity coefficient has been applied to LiCl, NaCl, KCl, RbCl, CsCl, and HCl in methanol-water mixtures at 25°C. The two parameters, _MX ⁽⁰⁾ and _MX ⁽¹⁾ , were obtained by the method of least squares. The same values of b and as for aqueous systems could be used for the methanol-water mixtures without greatly affecting the standard deviation of the fit. _MX ⁽⁰⁾ was found to decrease with methanol content for the alkali metal chlorides whereas _MX ⁽¹⁾ was found to increase. For HCl, however, a slight maximum and a minimum were found in the values of _MX ⁽⁰⁾ while a maximum was observed in the values of _MX ⁽¹⁾ .     

Crazes in amorphous polymers I. Variety of the structure of crazes and classification of different types of crazes

In investigating 0.5- to 5 m-thick deformed samples in a 1000 kV high-voltage electron microscope, the formation and structure of crazes were studied in different amorphous polymers (PS, SAN, PVC, and the highly radiation-sensitive polymers PMMA and PC). Different craze types were found and classified. There are some types of true crazes with a fibrillar structure or rather a homogeneous structure, which have to be distinguished from only craze-like deformation zones. A peculiarity was found in PMMA which produces a craze type different in structure from the well-known fibrillated crazes typical of PS.     

Electrothermal AAS studies of Sm, Eu, Dy, and Er separated from uranium

Summary Studies were conducted on the assay of Sm, Eu, Dy and Er separated from uranium using aqueous standards by electrothermal AAS with Massmann type graphite furnace. The working curves were found to be linear in the ranges Sm (1–10 g/ml), Eu (0.05–0.6 g/ml), Dy (0.1–0.8 g/ml) and Er (0.1–1.0 g/ml). The values obtained for synthetic samples agreed favourably with those obtained by emission spectrographic method. Experiments using pyrolytic carbon coated tubes with and without pretreatment by La, Ta and Y have shown an enhancement with treatment upto a maximum of 15% and improve the memory effect marginally. The effect of Ta treatment was found to be singularly useful in improving the general behaviour of Sm. The interference effects of lanthanides, other than the analyte, were found to be negligible. However, the presence of uranium was found to affect the absorbance. The absorbance of Eu was found to be nearly independent of uranium after an initial increase. On the other hand, the absorbance of other elements studied was found to drastically decrease after an initial enhancement. Detailed investigations of temperature dependence of absorbance were carried out using Eu, Dy and Er. The differences in the behaviour of these elements is attributed to probable differences in the modes of their atomization.

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Untersuchung von aus Uran abgetrenntem Samarium, Europium, Dysprosium und Erbium durch elektrothermische Atomabsorptions-Spektralphotometrie

Zusammenfassung Die Untersuchungen wurden mit Hilfe des Graphitrohrofens nach Maßmann durchgeführt. In folgenden Bereichen ergaben sich lineare Eichkurven: Sm 1–10 g/ml, Eu 0,05–0,6 g/ml, Dy 0,1–0,8 g/ml, Er 0,1-1,0 g/ml. Die aus synthetischen Proben erhaltenen Ergebnisse stimmten gut mit den durch Emissionsspektrographie erhaltenen überein. Versuche wurden mit Röhren mit pyrolytischen Kohlenstoffüberzug mit und ohne Vorbehandlung durch La, Ta und Y durchgeführt und ergaben eine bis 15%ige Steigerung durch die Behandlung sowie eine mäßige Besserung des Memoryeffektes. Eine Behandlung mit Ta war besonders für Sm vorteilhaft. Störungen durch andere Lanthanide waren vernachlässigbar. Uran beeinflußte jedoch die Absorption. Im Falle von Eu zeigte sich nach anfänglicher Zunahme fast eine Unabhängigkeit, während bei den anderen untersuchten Elementen nach anfänglicher Zunahme eine beträchtliche Abnahme auftrat. Mit Eu, Dy und Er wurde ebenfalls die Temperaturabhängigkeit der Absorption untersucht. Festgestellte Unterschiede im Verhalten werden auf unterschiedliche Atomisierung zurückgeführt.

     

Microwave-accelerated Wittig olefination of β-chloroacroleins

The first microwave assisted Wittig reactions of β-chloroacroleins with a stabilized ylide are described here. A combination of sodium ethoxide and toluene was found to be optimum and using this reaction condition a number of alkenyl-substituted benzopyran/benzo[b]oxepine/2-chromenone derivatives were prepared within few minutes. The microwave mediated process was found to be comparable with the conventional Wittig reaction in terms of product yields. All the products isolated were found to have E-geometry around the CC bond.     

Validation of a loss-free counting system for neutron activation analysis with short-lived indicators

The use of loss-free counting systems makes possible the exact correction for pile-up and dead-time losses during counting of a mixture of short-lived radionuclides even at very high count rates. However, counting statistics cannot be calculated by taking into account only the Poisson distribution of the incoming -quanta, such as is done in existing computer programs for -spectrometry. At moderate count rates Müller statistic was found to account for the observed variability between duplicate countings; however, at higher count rates the variability of weighing factors was found to be significant in comparison with the Müller statistic. While counting statistics could not be correctly estimated for short-lived species, experiments showed excellent accuracy for initial dead times up to 90%.     

Adsorption of N-Nitrosodiethylamine and N-Nitrosodimethylamine on Activated Carbon: A Pre-Concentration Procedure for Gas Chromatographic Analysis

In this study, a rapid pre-concentration procedure, which employs powdered activated carbon as a clean-up and pre-concentration material, is described for the gas chromatographic analysis of N-nitrosodiethylamine (NDEA) and N-nitrosodimethylamine (NDMA) in aqueous solutions. It was found that powdered activated carbon is suitable for the adsorption of volatile N-nitrosamine compounds from aqueous solutions. Adsorption efficiency with spiked beer samples (alcohol content 5% v/v) was found to be 80.5% (NDMA) and 89.4% (NDEA) and recovery of extraction from activated carbon was calculated as 82.1% (NDMA) and 89.7% (NDEA), respectively. The effect of 100µgmL^–1 of tannic acid on the adsorption was also studied, and no significant effect on the adsorption and extraction of volatile N-nitrosamine compounds was found.     

Utilization of tetrazolium blue for the colorimetric assay of tannins in tea

A simple, rapid and accurate colorimetric method is proposed for the determination of tannins, based on the reduction of tetrazolium blue in alkaline medium by tannins at 90 ± 2 °C for 15 min, leading to the formation of a highly coloured formazan derivative. Absorbance measurements were made at 527 nm and the calibration graph was linear for 0.2-9.0 g/ml of tannic acid. For more accurate analysis, the Ringbom optimum concentration range was found to be 0.5–8.2 g/ml. The relative standard deviation for the determination in a tea sample containing 7.55% tannins was 1.65%. Most of the ingredients commonly found in tea samples do not interfere with the determination. Several tea samples were analysed using the proposed method.     

Kinetics of reaction of methyl α-eleostearate with phenol

The kinetics of addition reactions between methyl α-eleostearate which forms the main chain of tung oil and phenol when catalyzed by an acid, p-toluene sulfonic acid, have been studied. The addition reactions, carried out with phenol was shown to be second order with regard to methyl α-eleostearate concentration and first order with regard to phenol concentration. The reactions were additions of two phenol molecules to one methyl α-eleostearate molecule, and it was presumed that they proceed in the two steps given below in which the first step is rate determining: ((1)) ((2)) The apparent reaction rate constant (l/mol min) was found to be 0.036 and its value was nearly equal to that in the case of m-cresol. The apparent activation energie (kcal/mol) was found to be 4.76 and its value was larger than that in the case of m-cresol.     

Selective liquid-liquid extraction of xylene isomers and ethylbenzene through inclusion by branchedα-cyclodextrins

Branched-cyclodextrins (CDs) such as glucosyl--CD(G--CD) were found to be very effective reagents for selective liquid-liquid extraction of xylene isomers and ethylbenzene since their inclusion complexes did not precipitate and handling of solids was not necessary. Reaction temperatures higher than room temperature did not increase the yield. The inclusion complexation proceeded fast. The liquid-liquid extraction process was found to be energy-saving and not time-consuming.     

Influence of hemicelluloses on the aggregation patterns of bacterial cellulose

Cellulose from the bacteriumAcetobacter xylinum was used as a model system for investigating the influence of other cell wall polysaccharides on the aggregation of cellulose. The patterns of aggregation of the bacterial cellulose were modified when the cellulose was produced in the presence of hemicellulose-like saccharides. The celluloses were found to be more like the I-type found in higher plant celluloses than the I-type in the control bacterial celluloses. The effects of isolation procedures on structure were also explored. It was found that the structures of isolated celluloses were influenced by the procedures used in isolation.Formerly The Institute of Paper Chemistry, Appleton, WI, USA.Retired     

Control of the synthesis of some biologically active substances by thin-layer chromatography

Summary The aim of this investigation was the synthesis of -aryl propionic acids which might be expected to have antiinflammatory activity. The total synthesis of -(4-benzoylphenyl)--methyl propionic acid was monitored by thin-layer chromatography. The adsorption of the compounds of interest was found to be dependent upon the polarity of the eluting solvents. The observed retentions were mathematicaly analysed, and the system that showed the best separation of reactants evaluated. A least squares method was used to determine the best geometric curve expressing the relationship between values for R_f and eluent composition.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Laboratory studies on the adsorption behavior of americium

With increasing global nuclear activities, there is a growing interest in understanding the migration behavior of transuranic elements in the terrestrial environment. The laboratory investigations on the adsorption behavior of AM(III) (10^–7M) in aqueous solutions showed that there was not adsorption of Am(III) on glass or polyethylene vials from aqueous solutions at pH<3. The rate of adsorption was found to be inversely related to the (H⁺) in the pH range 4–7. It was also found to be strongly influenced by stirring/shaking as well as by the presence of particulate matter in the aqueous phase. The presence of particulate matter (>0.6 m) in the aqueous solutions significantly inhibits the adsorption rate. Attempts to fit the kinetic data (collected on filtered [particle size >0.6 m] or unfiltered distilled water at pH 6) to the reversible or irreversible first order rate equation did not successfully indicate the complexity of the adsorption process. The presence of 20mg/liter of humic acid at pH 6.3 completely inhibits the adsorption of Am on glass surfaces.     

Hydrolysis of 2-aminoethanethiolsulfate ions

The kinetics of the acid catalyzed hydrolysis of 2-aminoethanethiolsulfate (AETS) ions were investigated. The dependence of the hydrolysis rate constant on acidity and temperature was determined. The hydrolysis rate equation can be expressed as where H_o is the Hammett acidity function. The rate constant, k, can be expressed as The pK_a's for the compound were measured and literature value of pK_a was found to be in error. The values determined in this study are pK_a1 < ?0.5 and pK_a2 = 9.1 ± 0.1. General acid catalysis of the hydrolysis reaction was found not to proceed to a significant degree. © 1994 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.