Method comparison study on soot-selective techniques

In a long-term field study at two locations with different air pollution levels several soot-selective measurement techniques were compared with a thermochemical method which measures non-extractable carbon (NEC) detecting the evolved CO₂ by means of coulometric titration. The attenuation measurement technique (aethalometer) and the aerosol photoemission method showed good correlations to NEC for concentrations ranging from 1.6g/m³ to 40.8g/m³. The specific mass absorption coefficient of black carbon with respect to NEC varied between 8.4m²/g and 13.7m²/g with respect to the measurement sites, but the value was found to remain constant at each site independent of seasonal or meteorological variations. The ratio of photoelectric signal to NEC varied between 16 fA·(g/m³)^–1 and 33 fA·(g/m³)^–1 depending on the age of the aerosol. The diurnal variations of that ratio showed strong similarities to the traffic patterns. Additionally a slight temperature dependence of this ratio was found for the aged aerosol with a proportionality factor of – 0.35 fA·(K·g/m³)^–1. With the reflectance measurement technique (smoke shade method) reliable NEC determination was not possible for NEC concentrations 5 g/m³.     

Evaluation of quantum yields in the presence of an absorbing additive

A method is proposed for the evaluation of quantum yields of photochemical reactions studied in the presence of absorbing additives using cylindrical sample tubes.

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Transition State Geometry and a Polar Effect in the Reactions of Peroxy Radicals with Oxygen-Containing Compounds

The reactions of structurally different peroxy radicals with the C–H bonds of oxygen-containing compounds (ketones, aldehydes, ethers, and esters) were analyzed in terms of a parabolic model. The enthalpies of these reactions and the activation energies of equienthalpic reactions of peroxy radicals with hydrocarbons were calculated, and the contribution of the polar interaction E to the activation energy was evaluated. The geometry parameters of the transition state were calculated with the use of an algorithm developed based on quantum-chemical calculations in combination with the intersecting parabolas method. It was found that the polar interaction resulted in a change in the configuration of the C···H···O reaction center in the transition state from linear to angular. A different angle (C···H···O) from 180° appeared in this case. The following linear correlation between E (kJ/mol) and cos (180° – ) was obeyed: cos (180° – ) = 1 + 6.76 × 10^–3E .     

Komplexe des Kobalts mit o-Methylbenzamidoxim

Zusammenfassung Die stufenweise Komplexbildung des Co²⁺ mit o-Methylbenzamidoxim (oMB) gibt in alkalischer Lösung zwei Komplexe, deren Zusammensetzung 11 und 12 ist. Die Bildungskonstanten wurden nach graphisch-logarithmischen Methoden bestimmt. Die Bildungskonstanten sind ₁=(4,1±0,6)·10⁴ und ₂ = 0,41 bei 25° C und Ionenstärke =1.

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Co(II) complexes of o-methylbenzamidoxime

In alkaline solution 11 and 12 complexes are formed stepwise from Co²⁺ and o-methylbenzamidoxime. The ligand numbers and the formation constants were determined from spectrophotometric data by logarithmic graphical methods. The formation constants are ₁=(4,1±0,6)·10⁴ and ₂ = 0,41 at 25° C and =1.

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Mit 3 Abbildungen     

Photometrische Bestimmung von Bor in hochreinen Chemikalien

Zusammenfassung Bor reagiert in Form des Tetrafluoroboratkomplexes mit dem basischen Farbstoff Methylenblau unter Bildung eines mit 1,2-Dichlorethan extrahierbaren Ionenassoziatkomplexes. Die optimalen Bedingungen für die photometrische Bestimmung von Mikromengen Bor werden ermittelt und das vorgestellte Verfahren hinsichtlich Empfindlichkeit, Genauigkeit und kleinster bestimmbarer Menge charakterisiert.Die Borbestimmung ist im Bereich von 0,25–2,5 g Bor mit einer relativen Standardabweichung von 3,8% für 1,0 g Bor möglich. Der molare Extinktionskoeffizient beträgt ₆₆₅=8,2·10⁴1·mol^–1·cm^–1, die Nachweisgrenze nach Kaiser 0,125 g Bor.Das Verfahren wurde zur Bestimmung von 10^–6 bis 10^–5% Bor in folgenden hochreinen Chemikalien eingesetzt: Methanol, Ethanol, Isopropanol, Aceton, Mineralsäuren, Essigsäure, Ammoniak und Wasserstoffperoxid.

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Photometric determination of boron in high-purity chemicals

Summary Boron reacts with fluoride to form borofluoride which itself reacts with the basic dye methylene blue forming a complex which can be extracted into 1,2-dichloroethane. Optimum conditions were established for the determination of microamounts of boron by an extraction-photometric method. The procedure presented has been characterized with regard to sensitivity, precision and detection limit.Boron can be determined within a range from 0.25 to 2.5 g with a relative standard deviation s _rel=3.8% for 1 g B. The absorptivity is ₆₆₅=8.2·10⁴1·mol^–1·cm^–1, the detection limit according to Kaiser was found to be 0.125 g B.The procedure was used to analyse high-purity chemicals (10^–6–10^–5% B) such as organic solvents, mineral acids, acetic acid, ammonia, hydrogen peroxide etc.

     

Path of “dry” electrons before localization in liquid hydrocarbons

Conclusions On the basis of measurements of values of in liquid hydrocarbons, it has been shown that the path length before localization of a photoliberated electron increases with increasing mobility of the excess electron, from approximately 40 Å (methylcyclohexane) to 200 Å (isooctane). In a liquid with10^–2 cm²/V·sec (methylcyclohexane, hexane), the localization takes place before or immediately after thermalization of the electron. In a liquid with>10^–1 cm²/V·sec, the electron passes through the main part of its path before localization, being in thermal equilibrium with the medium.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2198–2203, October, 1985.     

Temperature effect on the composition and activity of iron(III) stearate based organometallic catalysts in hydrogenation reactions

The observed temperature dependence of the composition of FeSt₃–AlEt₃ catalytic system indicates that with increasing temperature the maximum catalytic activity and the content of the associated polynuclear complex change in parallel. This complex probably plays a decisive role in catalytic processes.

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FeSt₃–AlEt₃ . . , .

     

Kinetics of triphenylphosphite ozonide consumption in reaction with triphenylphosphite

Kinetic regularities of triphenylphosphite ozonide reaction with triphenylphosphite have been studied at T=–75°C to –40°C. The rate of ozonide consumption is estimated as W=k₁[(C₆H₅O)₃P·O₃]+k₂[(C₆H₅O)₃P·O₃][(C₆H₅O)₃P], where k₁=(2.03±0.39)×10^–5s^–1(–50°C), 1gk₂=(3.82±0.33)–(6.61±0.32)/gq dm³/mol s and =2.303RT kcal/mol.

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–75°C –40°C . : W=k₁[(C₆H₅O)₃P·O₃]+k₂[(C₆H₅O)₃P·O₃][(C₆H₅O)₃P], k₁=(2,03±0,39)·10^–5–1(–50°C); 1g k₂=(3,82±0,33)–(6,61±0,32)/ /·, =2,303·RT /

     

Bestimmung von Chrom in menschlichem Serum und Plasma mit der flammenlosen Atomabsorptions-Spektrophotometrie

Zusammenfassung Die bis heute in der Literatur mitgeteilten Werte für Chrom im Serum nüchterner gesunder Probanden unterscheiden sich um Größenordnungen. Die in der vorliegenden Arbeit mitgeteilten Untersuchungen betreffen die analytische Problematik der Chrombestimmung mit Hilfe der flammenlosen Atomabsorptions-Spektrometrie, wobei aufgezeigt wird, daß diese Methodik für die Chrombestimmung in biologischem Material ohne großen statistischen Aufwand zu keiner sicheren Beurteilbarkeit und Interpretierbarkeit der gemessenen Werte führt. Mit Hilfe synthetischer Chromkomplexverbindungen werden die Probleme der Standardaddition zur Chrombestimmung untersucht. Unter Berücksichtigung der Blindwerte und der daraus resultierenden Nachweisgrenze sowie Garantiegrenze für Reinheit, wurde Chrom in einem Standardreferenzmaterial (1569 Brewers yeast [U. S. National Bureau of Standards]) im Rahmen eines Ringversuchs zur Chromanalyse sowie im Serum und Plasma von 41 Probanden bestimmt. Für das Referenzmaterial wurde ein Wert von 45±4 mol/kg (2,3±0,2 g/g) ermittelt. Der Referenzwert betrug 41±1 mol/kg (2,12±0,05 g/g). Im Serum wird eine lognormale Verteilung der Chromkonzentration mit den zentralen Parametern ±_M=132,2 nmol/l (0,72,2 g/l) ermittelt. Im Plasma lagen die Werte zwischen 20 und 30 nmol/l (1–1,5 g/l). Aufschluß, Durchführung der Bestimmung sowie die biologische Bedeutung und Interpretation des Parameters Chrom im Serum und Plasma werden eingehend diskutiert.

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Determination of chromium in human serum and plasma by flame-less atomic-absorption spectrophotometry

Summary Concentrations of Cr in serum of overnight fasting volunteers differ over a wide range in the literature. The investigations of the analytical problems of Cr determination by flameless atomic absorption spectrometry underline the necessity of statistical methods for the interpretation of the measurements of Cr in biological matrices. With nine different synthetic chromium complexes the method of standard addition was investigated. Considering the blank values, the limit of detection and the limit of guarantee for purity, Cr was determined in the standard reference material 1569 brewers yeast (National Bureau of Standards) with 45±4 Mol · kg^–1 (2.3±0.2g·g^–1), compared with the reference data 41±1 Mol·kg^–1 (2.12±0.05 g±g^–1). In serumuuuuu we found a lognormal distribution with the central parameters 132.2 nMol ·1^–1 (0.72.2 g·1^–1). In plasma the values were in the range between 20 and 30 nMol·1^–1 (1–1.5 g·1^–1). The ashing process and the determination are demonstrated and discussed in detail.

     

Heterobinuclear and heterotrinuclear transition-metal μ-allenyl complexes

Binuclear and trinuclear transition-metal -allenyl complexes—especially mixedmetal complexes—are reviewed. In recent years, a number of such compounds have been prepared by use of several synthetic methods. The most general of these methods, viz. reactions of metal propargyls and of the lower nuclearity metal allenyls with low-valent metal complexes such as metal carbonyls and platinum(0) compounds, are considered in some detail. The structures of the binuclear metal -¹,²- and -³,²-allenyl complexes and of the trinuclear metal ₃-¹,²,²-allenyl complexes—both triangular and open—are presented and compared. Trends in the¹H and¹³C NMR spectroscopic properties of these compounds are examined. Some aspects of reaction chemistry of the heteronuclear platinum-ruthenium -¹,²-allenyl complexes are presented.     

Nuclear interferences of uranium and thorium in a reactor neutron activation analysis determination of cerium using the radionuclides141Ce and143Ce

The interference contributions of uranium and thorium to the determination of cerium based on radionuclides¹⁴¹Ce and¹⁴³Ce produced by irradiation in a reactor core was determined. The values of the interference contributions for¹⁴¹Ce were 0.28±0.01 g Ce/g U and /2.01±0.05/x10^–3 g Ce/g Th, and for¹⁴³Ce 1.33±0.03 g Ce/g U and /9.0±0.2/x10^–3 g Ce/g Th.     

Capillary rise of liquids in rectangular tubings

The capillary rise of liquids was investigated in square capillary tubings of different dimensions (e. g. 300 m · 300 m to 1000 m · 1000 m) in the temperature range 25° to 35°C.The data were fitted to an equation:=1/2 · ·g · (S · (C ·H/2 +C ·S)) where is the surface tension of the liquid,S is the side length of the square tubing,H is the capillary rise,C (= 1.089) is a capillary constant.     

Komplexbildung im System Ni2+—o-Methylbenzamidoxim

Zusammenfassung Die Komplexe des Ni²⁺ mit o-Methylbenzamidoxim wurden in neutraler und in alkalischer Lösung spektrophotometrisch untersucht. Die Bildungskonstanten sindK ₁=40 für 11 undK ₂=1,7·10² für 12 in neutraler Lösung und ₁ = =(3,92 ±0,2) · 10⁴für 11 und lgK = lg ₁ + lg ₂ = 3,45 ± ±0,15 für 12 bei 25° und =1 in alkalischer Lösung.

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Complex formation in the systemeNi ²⁺—o-methylbenzamide oxime

The complexes of Ni²⁺ with o-methylbenzamide oxime were investigated spectrophotometrically in neutral as well as in alkaline solution. The formation constants areK ₁=40 for 11 andK ₂=1.7·10² for 12 in the neutral solution and ₁ = =(3.92 ±0.2) · 10⁴ for 11 and lgK = lg ₁ + lg ₂ = 3.45 ± ±0.15 for 12 at 25° and =1 for the alkaline solution. *** DIRECT SUPPORT *** A3615139 00007

     

Development of a Sequential Injection Analysis Device for the Determination of Total Polyphenol Index in Wine

A sequential injection analysis method is developed for the determination of the total polyphenol index in wines. The determination is based on the Folin-Ciocalteu reaction, which is monitored spectrophotometrically. Interactions between experimental variables and their optimal levels were investigated using factorial designs. The proposed system is fully computerised and is able to monitor polyphenol index in real samples of white, sweet and red wines. The calibration graph is linear from 5 to 200mg·L^–1 using Tannic acid as standard, with a detection limit of 3.2mg·L^–1. Interferences are studied. For validation purposes the proposed methodology was applied to the determination of the total polyphenol index in different types of wines and compared with earlier alternatives in order to assess their performance.     

Top soil environmental radioactivity in Akwa Ibom State of Nigeria

A survey of top soil environmental radioactivity in Akwa Ibom State of Nigeria has bean investigated. The results vary considerably from one environment to another ranging between a minimum of 161 mBq·g^–1 and a maximum value of 648 mBq·g^–1 -activity. The work reveals that hospitals and health centres lead in top soil radioactivity with the highest mean values of (378 mBq·g^–1) and (294 mBq·g^–1) followed closely by industrial areas with mean values of (372 mBq·g^–1) and (283 mBq· g^–1) trailing beaches and recreation centres having average values of (364 mBq·g^–1) and (273 mBq·g^–1). Lower levels of top soil radioactivity were observed mostly in environments with high level human interaction activity such as schools, offices, environments and recreation centres. An overall top soil mean of 342 mBq·g^–1 -activity, 271 mBq·g^–1 -activity and 71 mBq·g^–1 -activity were observed in the State.     

Complexometric determination of mercury(II) in waters by spectrophotometry of its dithizone complex

This paper presents a new method for the determination of Hg(II) in waters, using indirect spectrophotometric measurements of the Hg(II) dithizone complex. The reagent is a mixture of dithizone, CDTA (1,2-cyclohexylene-dinitrilo-tetraacetic acid), thiourea, ethylic alcohol and glycine. Sensitivity and working range are 0.4 g · l^–1 and 2–100 g · l^–1, respectively. A comparison of the results with those of the cold-vapor atomic absorption spectrometry shows a good correlation for different samples revealing only small interferences. The new method is well suited for on-line measurements, easy to run and has low cost equipment.     

Fallout analysis of atmospheric water precipitations

Summary A rapid ion-exchange method for the determination of ¹⁴⁴Ce, ¹³⁷Cs, ⁸⁹Sr, ⁹⁰Sr and ¹⁴⁰Ba in 2–30 liter samples of atmospheric water precipitations is described. The samples, containing up to 300 mg of calcium, are sorbed on a specially shaped column filled with Dowex 50, X-8 or Dowex 50W, X-8. Radio-cerium and radio-caesium are stripped from the column with 0.6 M ammonium glycolate/ 0.2 M NaCl, pH 5, radio-strontium and radio-barium with 0.15 M ammonium citrate, pH 7.5. The isolated radio-nuclides are counted on a low-background beta-counter: ¹⁴⁴Ce as CeO₂, ¹³⁷Cs as Cs-dipicrylaminate, ⁸⁹Sr/⁹⁰Sr as SrCO₃, ⁹⁰Y as Y₂O₃, and ¹⁴⁰Ba as BaCO₃. The mean chemical yields amount to 95% for cerium, 85% for caesium, 95% for strontium, 95% for yttrium and 65% for barium. With parallel determinations at levels of a few picocuries, the deviations of the results from the respective mean values generally do not exceed ± 5%. With a 30 l sample the limit of detection amounts to 0.005 Ci/l for ¹⁴⁴Ce, 0.006 Ci/l for ¹³⁷Cs, 0.005 Ci/l for ⁹⁰Sr, and 0.006 Ci/l for ¹⁴⁰Ba.

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Zusammenfassung Es wird eine schnelle Ionenaustauschmethode für die Bestimmung von ¹⁴⁴Ce, ¹³⁷Cs, ⁸⁹Sr, ⁹⁰Sr und ¹⁴⁰Ba in 2–30 l Proben von atmosphärischen Wasser-Niederschlägen beschrieben. Die Proben, mit einem Calciumgehalt bis zu 300 mg, werden in eine besonders gestaltete, mit Dowex 50, X-8 oder Dowex 50 W, X-8 gefüllte Säule eingewaschen. Radio-Cer und Radio-Caesium werden mit 0,6 M Ammoniumglykolat/0,2 M NaCl, pH 5, Radio-Strontium und Radio-Barium mit 0,15 M Ammoniumcitrat pH 7,5 eluiert. Die isolierten Radio-Nuklide werden in einem Beta-Antikoinzidenzzähler gemessen: ¹⁴⁴Ce als CeO₂, ¹³⁷Cs als Cs-dipikrylaminat, ⁸⁹Sr/⁹⁰Sr als SrCO₃, ⁹⁰Y als Y₂O₃ und ¹⁴⁰Ba als BaCO₃. Die mittlere Rückgewinnung der zugesetzten Träger beträgt für Cer 95%, 85% für Caesium, 95% für Strontium, 95% für Yttrium und 65% für Barium. In Parallelbestimmungen mit Gehalten von einigen Ci/l, überschreiten die Abweichungen der Ergebnisse von den entsprechenden Mittelwerten im allgemein nicht 5%. Bei einer 30 l-Probe beträgt die untere Nachweisgrenze 0,005 Ci/l für ¹⁴⁴Ce, 0,006 Ci/l für ¹³⁷Cs, 0,005 Ci/l für ⁹⁰Sr und 0,006 Ci/l für ¹⁴⁰Ba.

     

Komplexe des zweiwertigen Kobalts mit p-Methylbenzamidoxim

Zusammenfassung Die Komplexbildung des Kobalts mit p-Methylbenzamidoxim (pMBz) in alkal. Lösung wurde spektrophotometrisch untersucht. Die Ligandenzahl und die Bildungskonstanten wurden nach logarithmischen Methoden bestimmt. Bei niedrigeren Konzentrationen des pMBz entsteht ein Komplex 11 (bei höheren 12). Die Bildungskonstanten bei 25°C und =0,02 sind ₁=(2,95±±0,06)·10⁵ und =21,±0,3.

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Co(II) complexes of p-Methylbenzamideoxime

The complex formation of cobalt with p-methyl benzamidoxime in alkaline solution was investigated spectrophotometrically, and the ligand number and the formation constants were determined by logarithmic methods. At low pMBz concentrations a 11 complex is formed and at higher ones a 12 complex. The formation constants are ₁=(2,95±0,06)·10⁵ and ₂=21,8±0,3 at 25°C and =0,02.

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Mit 6 Abbildungen