In memoriamMichell J. Sienko

Calcium urate hexahydrate, Ca(C₅H₃O₃N₄)₂ · 6H₂O, has been synthesized for the first time. A tentative assignment of some infrared and Raman bands is given by referring to the isotopic frequency shifts, group frequency considerations, Raman intensities as well as to the spectrum of potassium salt. The spectroscopic data suggest that there are, at least, two types of water molecules in the unit cell. Centrosymmetric unit cell is proposed to explain the spectral features of this compound. X-Ray powder diffraction data are also given.     

Bewertung von glättungsexperimentenEvaluation of curve-smoothing techniques

Conditions for curve smoothing can be compared experimentally by simulation or theoretically by applying information theory. Simulation experiments provide the conditions either for optimization of the signal/noise ratio or for minimizing the systematic error; the results presented are easily evaluated in practice. Information theory assumes that loss of information will not be caused by the smoothing procedure. Conditions for maximal noise improvement for a preset systematic error are then obtainable; the regularities are easily interpreted from graphs.     

Reaktionskalorimeter und reaktionsrohrbehälter mit verbessertem wärmedurchgangskoeffizientenReaction calorimeter and agitated reaction vessel with improved overall heat transfer coefficient

In present types of reaction calorimeters and agitated reaction vessels the overall heat transfer coefficient between reaction mixture and cooling fluid is low, caused by the low heat transfer coefficient on the cooling fluid side. Consequently the thermal response time is high and a quasi-isothermal reaction is difficult to obtain. A new construction of a cylindrical double wall reaction vessel is presented which yields a higher overall heat transfer coefficient than conventional constructions. The cooling fluid flows through a helically shaped flow path between the walls. The outer wall is especially bulged to improve strength and heat transfer. Two reaction vessels are tested yielding good results.     

A new alkylamidation reactionRegiospecific condensation of carbanions on cyclo 1,3- oxoimminium salts

Cyclo 1,3-oximminium salts are found to react regiospecifically with functional carbanions. Steric effects induced at the C-2 site on salts or at the carbanionioc centers promote the condensation at the C-5 or C-6 opposite sites. A bulky substituent such as 2-mesityl group is a powerful auxiliary which not only modifies the steric environment at the reactive C-2 site but also contributes to enhance the reactivity of the cyclo oxoimminium ring.     

Microcalorimetre pour l'etude des reactions en chimie du fluorMicrocalorimeter for the study of reactions in fluorine chemistry

A miniaturized differential calorimeter (Type M.C.B.)\b7 specially fitted for fluorine chemistry is described. It includes two identical cells connected through a chromel/constantan thermo-électric element; these two cells are equiped each with a fixed value calibrating resistance and a thermocouple. The sensitivity of the aparatus is 70μv/mW with a time lag of 30 To 35 secondes the usable temperature range with lies between - 200 To + 650°C depends on the character of the reactant. The temperature variation of system can be programmed up to 3°C/mn. The apparatus has been concerned in two distinct parts, on works in high vacuum and recieves the reactants, the other works in a protected atmosphere or vacuum. This microcalorimeter has been used for measurement of heats of adsorption, of complexation and of decomposition: of heats of solid/solid and solid/liquid transitions, of heats of dissolution and of mixing, and also for the determination of spécific heats of fluorinated and other compounds.     

Effizienz der regression in der röntgenspektrometrieThe efficiency of regression calculations in x-ray spectrometry

(The efficiency of regression calculations in x-ray spectrometry)Regression fitting by the least-squares technique minimizes analytical errors. Examples in the literature indicate the possible errors of the method with regard to overfitting, extrapolation and gaps in the concentration range of the standard samples. Strict consideration shows that in practice such errors are insignificant. The problem of unnecessary parameters is discussed; it is shown that regression fitting can cope with such parameters without increased error. The method can also provide a criterion for the necessity of parameters in calibration functions. The most important sources of error in x-ray spectrometry, which are enumerated, do not include the regression calculations.     

Bestimmung und abtrennung von sauerstoffverunreinigungen in reinst-selenThe determination and separation of oxygen impurities in high-purity selenium

(The determination and separation of oxygen impurities in high-purity selenium)By distillation in high vacuum, high-purity selenium is almost completely freed from impurities caused by metallic elements, oxides and water. If bulk vitreous selenium has a suitable thermal history, the oxygen content may be determined from the intensity of the oxide absorption band at 932 cm^?1 in the i.r. spectrum of the glass. In distilled selenium this content is < 1 × 10^?4 wt.< %.     

Stereoselective additions to carboxylic acid dianions and β-lactone substituted ester enolatesApplication to the synthesis of racemic epi-blastmycinone, δ-multistriatine,paraconic esters and lignantype dilactones

New stereoselective syntheses are reported for racemic 4-epi-blastmycinone (6) and δ-multistriatine (13) utilizing the anti-configurated γ, β-unsaturated β-hydroxy-carboxylic acids 2a/b. A diastereo- and enantioselective aldoltype addition of phenylacetic acid dianion to benzaldehyde has been achieved by employing optically active alkoxide amide bases. Finally, highly stereocontrolled additions to the novel β-lactone substituted ester enolates 22 are described.     

Entwicklung einer flieβinjectionsmethode zur bestimmung von chlorid im spurenbereich durch leitfähighkeitsdiffernzenA flow-injection method for the determination of trace amounts of chloride

The indirect determination of chloride in water is based on measurement of the difference in conductivity after the sample has passed through ion-exchange columns in the hydrogen form and silver form. The linear response range is about 0.5–10 μg g^?1 chloride (with 3 μg g^?1 nitrate and 5 μg g^?1 sulfate); the detection limit is about 50 ng g^?1 chloride but depends strongly on the concentrations of other anions.     

Dosage de la silice des silicates,apres distillation,par gravimetrie du molybdosilicate de quinoleineThe determination of silica in silicates by distillation and gravimetry as quinoline 12-molybdosilicate

The determination of silica in silicates by distillation and gravimetry as quinoline 12-molybdosilicateQuantitative distillation of silica as hexafluorosilicic acid is followed by gravimetric determination of the silicate as quinoline 12-molybdosilicate. Precise results are obtained even when the samples contain phosphorus and fluorine. Compared to classical insolubilization procedures with strong acids, the proposed method is quicker and more sensitive, being applicable down to ca. 1 mg SiO₂. Its application is limited to silicates decomposed by hot sulphuric acid—hydrofluoric acid mixtures. The accuracy of the procedure is confirmed by the results for numerous reference standards.     

Preliminary communicationA remarkable intramolecular difference in local scrambling rates for two Mo(CO)3 groups and absence of metal-to-metal scrambling

The carbon-13 NMR spectrum of guaiazulenedimolybdenum hexacarbonyl has been examined from ?112 to +92°C. There is local scrambling of the three CO's on each Mo atom but at vastly disparate rates; resonances for one set coalesce below ?112°, those of the other at about ?30°C. No scrambling of CO's from one metal atom to the other is observed.     

Komplexbildung und extraktion von kupfer und eisen sowie gallium mit isomeren langkettigen alkylchinolin-8-olenComplex formation and liquid-liquid extraction of copper,iron and gallium with isomeric long-chain alkylquinolin-8-ols

The extraction of copper(II) and iron(III) with the 5-nonyl-, 5- and 7-decyl- and 5-chloro-7-decyl derivatives of quinolin-8-ol was studied with chloroform, benzene or toluene as the organic solvent. Isomeric extractants show only small differences and are very suitable for the extraction of copper and its separation from iron, similarly to Kelex 100 (7-dodecenylquinolin-8-ol). With these derivatives log K_ex values are ?5.18 to ?6.08 for iron(III) with pH_0,5 = 4.5 to 5, whereas log K_ex values are 1.54 to 1.82 for copper(II) with pH_0,5 ≈ 1.35. The chelates of copper, iron and gallium with isomeric ligands, isolated as the solids, have characteristic differences in melting points and solubilities. To extract gallium from alkalin solution, only 7-alkyl-8-quinolinols proved as favourable.     

Einsatz von rechenanlagen in der emissionsspektrochemie für aufstellung,bewertung und linearisierung der analytischen eichgeradenThe use of computers in emission spectrometry for the establishment,evaluation and linearization of analytical calibration curves

(The use of computers in emission spectrometry for the establishment, evaluation and linearization of analytical calibration curves)The problems of establishing optimum linear calibration lines for atomic emission spectrometry are discussed, with emphasis on use of photographic recording techniques. The calculation procedure, which is based on the least-squares method, generates additional statistical values which permit the linearity to be checked. As the desired linearity is not always achieved at the first attempt, the process is repeated after unreliable input data have been removed.     

Coumarin-6-sulphonyl chloride: a novel label in fluorimetry and phosphorimetry Part 1. Synthesis and Luminescence PropertiesagauS.M.Z. Al-Kind1

Coumarin-6-sulphonyl chloride was synthesized from coumarin in a single step and characterized. It was used to label amines, amino acids and phenols in mild conditions. The products of such reactions show intense fluorescence in alkaline solutions as a result of a photolytic ring-opening reaction. The derivatives are also phosphorescence at 77 K without ring opening.     

Inversvoltammetrische spurenbestimmung von Antimon(III) und Antimon(V) in aquatischen umweltproben nach selektiver extraktionStripping Voltammetry of Traces of Antimony(III) and Antimony(V) in Natural Waters After Selective Extraction

The biological activity of antimony depends on the oxidation state. The Sb(III) and Sb(V) states can be distinguished, even in the ng l^?1 range, by coupling extraction with ammonium pyrrlidenedithiocarbamate into methyl isobutyl ketone (APDC/MIBK), or N-benzoyl-N-phenylhydroxylamine (BPHA) into chloroform, with anodic stripping voltammetry (a.s.v.). After complex formation with APDC in acetate-buffered medium, Sb(III), but not Sb(V), is extracted into MIBK and quantified by a.s.v. Antimony(V) is quantified in the aqueous phase after removal of Sb(III) by extraction with BPHA into chloroform from the medium acidified with nitric acid. The applicability of the proposed separation/a.s.v. method is demonstrated for samples of rain, snow and water from a dredging operation. The stability of the two antimony species is examined for natural waters with Sb(III) and Sb(V) added; possibilities of stabilization are described. The precedures should be suitable for speciation of antimony in relatively unpolluted waters.     

Séparation chromatographique des lanthanides en deux groupes basée sur des différences dans la cinétique de décomposition des complexes lanthanides-macrocyclesChromatographic separation of lanthanides into two groups based on kinetic differences in the decomposition of macrocycle/lanthanide complexes

The separation of the lanthanides in two groups, based on differences in decomplexation rates of the LnDOTA entities (DOTA = 1,4,7,10-tetraazacyclododecane-N,N′,N″,N?-tetraacetic acid), is achieved on a sulphonate cation-exchange column (H⁺ form). The yttrium earths, from terbium to lutetium, are eluted first as Ln-DOTA-H species with 1.25 M HCl; the light lanthanides, from lanthanum to samarium inclusive, are eluted as uncomplexed ions at the end of the chromatogram, with more concentrated hydrochloric acid. Given an equimolar mixture of the Eu-DOTA and Gd-DOTA complexes as starting solution, 40% of the gadolinium can be recovered free from europium at the start of elution and 47% of the europium free from gadolinium at the end of the elution.     

Extraction de l'acide oxalique par formation de paires d'ions et application au dosage de l'acide oxalique urinaireExtraction of oxalic acid by ion-pair formation with application to the determination of oxalic acid in urine

Extraction of oxalic acid by ion-pair formation with application to the determination of oxalic acid in urineThe yield of ion-pair extraction of oxalic acid by trioctylamine and triisooctylamine in chloroform depends on the pH of the aqueous phase. The optimum pH is 2.7, proving that hydrogenoxalate ion is the extractable form. Extraction yield depends on the acid used for pH adjustment and dissolution of the calcium oxalate formed in complex medium. The best results are obtained with hydrochloric and sulfuric acids and with trioctylamine extraction. This extraction was applied to oxalic acid determination by colorimetry and gas chromatography in urines from twenty healthy patients. Mean excretion was found to be $\text{0.30 mmol}\text{24 h.}$ Extraction yields lie between 94 and 106%.     

Determination de l'etain dans les sediments et les boues de stations d'epuration par spectrometrie d'absorption atomique avec generation d'hydruresDetermination of tin in sediments and sewage sludges by atomic absorption spectrometry with hydride generation.

The conditions for the determination of tin in sediments and sewage sludges by atomic absorption spectrometry with hydride generation are evaluated. Hydride generation is achieved in a 0.4 M nitric acid/0.2 tartaric acid solution. The effects of hydrochloric, nitric, sulfuric and hydrofluoric acids are discussed. Matrix effect and interferences from other trace elements are studied. Seven sample decomposition procedures are compared. Refluxing with a (1 + 3) niric acid/hydrochloric acid mixture was the preferred procedure for decomposing such samples.