Identification of amber and imitations by near infrared reflection spectroscopy

Imitations of amber have been prepared since a long time, but the number of imitations is increasing since modern polymers are available. At present, many imitations are based on a few synthetic polymers and even experts have some problems in distinguishing between real and falsed amber without destruction of the material. IR-Spectroscopy or pyrolysis combined with gas chromatography/mass spectrometry are very efficient methods in identifying amber and imitations but these methods need a sample preparation. By means of near infrared reflection spectroscopy it is possible to identify amber and imitations without any sample preparation in a short time. Optimization of the method and the application are discussed.     

Die Beziehungen zwischen Adsorptionswärmen,Oberflächen-spannungen und Reaktionswärmen bei dem ReaktionstypusA starr +B gasförmig ⇄AB starr

Zusammenfassung Wird die gesamte Energietönung eines Vorganges vom TypusA starr +B gasförmig AB starr mitE ₁ bezeichnet, die Energie der Chemoadsorption vonB anAB mitE ₂, die der Oberflächenspannung entsprechende, auf 1 Mol sich beziehende Oberflächenarbeit bei der PhaseA mitE ₃ und bei der PhaseAB mitE ₄, so besteht die BeziehungE ₁ +E ₃ –E ₂ –E ₄ =0 . Der isotherme Abbau nach derGibbsschen Funktion kann nur stattfinden, wennE ₃ vergleichsweise sehr groß (unendlich) ist, derjenige nach derLangmuirschen Funktion, wennE ₃ sehr klein (Null) ist.     

Reaktionen an komplexgebundenen liganden: XXXVI. Synthese und oxidationsverhalten von M(CO)5-komplexen (M = Cr,Mo, W) mit amin- und benzochinondiimin-liganden

The oxidation of yellow Cr(CO)₅NH₂R complexes (NH₂R = aniline, m-toluidine, 3,5-xylidine, m-anisidine) with Pbac₄ gives deep blue to deep purple coloured compounds, which have been identified as the respective [Cr(CO)₅(N-phenyl-1,4-benzochinon-diimine)] complexes. Oxidation of the p-phenylenediamine complex yields [(OC)₅CrHNC₆H₄NHCr(CO)₅], which is also deep blue. The binuclear blue complex [{Cr(CO)₅}₂HNC₆H₄NC₆H₅] is obtained by treating Cr(CO)₅THF with the free ligand in THF/hexane; it dissociates rapidly in acetone to form [Cr(CO)₅HNC₆H₄NC₆H₅] and Cr(CO)₅. Analogous Mo(CO)₅ and W(CO)₅ complexes could not be obtained. The oxidation of [W(CO)₅(m-anisidine)] by I₂ yields [W(CO)₄I]₂. All the compounds were characterized by spectroscopic methods as well as by elemental analysis.     

ESR.-Spektrum von Diphenylpicrylhydrazyl (DPPH)

The ESR. sprectra of DPPH in mixed organic solvents have been measured with a K-band superheterodyne spectrometer and self-locking magnetometer with high precision. Approximately 150 lines have been resolved in the spectra. Both the zero and first order derivative spectra were analyzed by a line shape analysis program for determination of the coupling constants. The smallest coupling constant was found to be 377 ± 5 mG, all other coupling parameter are multiples of this constant. A set of most probable coupling constants is given. The two nitrogen coupling constants are found to be equal within experimental error, and there exist several rotational relations and several possible assignments.     

Electronic detection of the enzymatic degradation of starch

[reaction: see text] The enzymatic degradation of starch can be monitored electronically using single-walled carbon nanotubes (SWNTs) as semiconducting probes in field-effect transistors (FETs). Incubation of these devices in aqueous buffer solutions of amyloglucosidase (AMG) results in the removal of the starch from both the silicon surfaces and the side walls of the SWNTs in the FETs, as evidenced by direct imaging and electronic measurements.     

Study on labeling conditions of125I-synkavit by the iodogen method

Labeling conditions of synkavit (2-methyl-1,4-naphthoquinol disodium phosphate) with iodine-125 have been studied. In this study, labeling temperature, reaction time, successive using of iodogen coated tubes, iodogen amount and synkavit concentrations have been determined to get optimum conditions for maximum labeling. Final results showed that when the labeling temperature, reaction time, synkavit concentration, and iodogen amount were, at room temperature, 15 min (in the case of successive using of three iodogen coated tubes), 2 mg ml^–1 and 5 mg, respectively; labeling yield was 90% and specific activities of the order of 555 GBq mmol^–1 (15 Ci mmol^–1) have been obtained.     

Influence of structural changes on the ion selectivities of magnesium ionophores based on malonic acid diamides

In an investigation of octamethylene bis(malonic acid diamides) and their selectivities for magnesium, it was found that presence of secondary amides within the particular ionophore played a considerable role in the enhancement of magnesium selectivity. Similar effects in other ionophores, i.e. tris(malonic acid diamides), were thus systematically looked at with the help of selectivity measurements with the hope of optimizing the number of secondary and tertiary amides so as to improve the magnesium selectivity. The syntheses of several investigated tris(malonic acid diamide) isologues are equally reported.Deceased in November 1992     

A vibrational spectroscopic study of the adsorption of 4,4′-bipyridyl by sepiolite and smectite group clay minerals from Anatolia (Turkey)

The adsorption of 4,4-bipyridyl by natural sepiolite and smectite group clay minerals (bentonite, hectorite and saponite) from Anatolia (Turkey) has been studied using vibrational spectroscopy. Investigation of Fourier-transform infrared and Fourier-transform Raman spectra of adsorbed 4,4-bipyridyl indicate the presence of chemisorbed species. However, any evidence for the generation of anionic species on the surface of the phyllosilicates has not been detected. It is proposed that the adsorbed bipyridyl molecules on sepiolite are centrosymmetric and H-bonded to the surface hydroxyls through both the nitrogen lone pairs as bidentate ligands. The adsorbed bipyridyl molecules on the smectite group clays are coordinated to exchangeable cations both directly and also indirectly through water as monodentate ligands. XRD patterns of the clays studied are also recorded.     

Radiometric titration based on colloidal and slow precipitate formation

Fluoride ions and, in about 0.005M concentration, tungstate ions form gelatinous precipitates, poorly soluble in water, with calcium ions. The radiometric determinations of the above ions are based on these reactions. Accurate radiometric determination can be carried out only if the gelatinous precipitate formed during titration can be properly separated from the solution. It has been found that in the case of fluoride ions the application of crystalline, easily filtrable Ca(COO)₂·H₂O or CaCO₃, and in the case of tungstate ions the application of CaWO₄ precipitate improves the filtration properties of⁴⁵CaF₂ and⁴⁵CaWO₄, respectively, formed during titration, whereby the radiometric determinations of the above ions become possible. Titrations were carried out with 0.05M and 0.005M CaCl₂ solutions, labelled with⁴⁵Ca.     

Sparteine-mediated asymmetric nucleophilic substitution at prochiral, sp(3)-hybridized carbon

[reaction: see text] ++-Phenyl-1,3-dioxolanes (1) react with organolithium reagents (2), associated with (-)-sparteine, in the presence of BF(3).OEt(2) to afford chiral monosubstitution products 3. Enantioselectivity is highest if both 1 and 2 carry alkyl substituents in the ortho position. However, the enantioselectivity decreases in the case of very bulky substituents such as tert-butyl or phenyl.