Determination of total carbon and total organic carbon from volatile air pollutants

Summary The method developed based on the determination of TC and TOC in the form of the total amount of CO₂ requires application of the proper techniques for the final determination of CO₂. The possibility of using a stream of carrier gas at a convenient flow-rate for desorbing quantitatively CO₂ concentrated on a molecular sieve permits use of a wide variety of known analytical techniques for the final determination of CO₂. Various methods were compared on the basis of both absolute and calibration measurements. The absolute methods chosen were gravimetric (classical or an automated version based on application of a gravimetric automat and automatic recording balance), thermogravimetric analysis and coulometry. The calibration methods included thermal conductivity, the flame-ionization detector (after conversion of CO₂ into methane) and infrared absorption. Usefulness of the methods was evaluated on the basis of comparative statistical analysis of experimental data with respect to precision (Snedecor'sF-test and Bartlett'sU ²-test) and accuracy (Student'st-test).

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Zusammenfassung Das entwickelte Verfahren zur Bestimmung des TC- und TOC-Gehaltes in Form der gesamten Menge CO₂ erfordert die Anwendung geeigneter Analysentechniken zur Endbestimmung dieser Verbindung. Die Möglichkeit einer Desorption des am Molekularsieb angereicherten CO₂ in einem Gasstrom mit geeignetem Durchfluß erlaubt zur Endbestimmung von CO₂ die Anwendung einer Reihe verschiedener Analysenverfahren. Die Anwendbarkeit verschiedener, auf Absolutverfahren und auch auf relativen Messungen beruhender Methoden wurde vergleichend untersucht. Die folgenden Methoden zur CO₂-Bestimmung wurden gewählt: die Gravimetrie (klassische oder automatisierte unter Einsatz eines Wägeautomaten und einer registrierenden Waage), die Thermogravimetrie und die Coulometrie. Von den relativen Methoden wurden die Thermokonduktometrie, der Flammenionisationsdetektor (nach Umsetzung von CO₂ zu Methan) und das IR-Absorptionsmeßverfahren geprüft. Die Anwendbarkeit der Methoden wurde mit Hilfe statistischer Prüfverfahren beurteilt, wobei die Präzision (SnedecorsF-Test und BartlettsU ²-Test) und die Genauigkeit (Studentst-Test) der erhaltenen Analysenwerte verglichen wurden.

     

Bond energy, aromatic stabilization energy and strain in IPR fullerenes

Various models applied to DFT structures and energies of 2-D and 3-D aromatic molecules shed new light on the effects of strain and aromaticity in these systems. The cyclic pi electron delocalisation does not stabilize the fullerene C60 formation; and 5-6 and 6-6 CC bonds have near-identical bond stretch potentials.     

Intake of 210Po, 234U and 238U radionuclides with beer in Poland

²³⁸U, ²³⁴U and ²¹⁰Po activity concentrations were determined in beer in Poland by alpha-spectrometry with low-level activity silicon detectors. The results revealed that the mean concentrations of ²³⁸U, ²³⁴U and ²¹⁰Po in the analyzed beer samples were 4.63, 4.11 and 4.94 mBq·dm⁻³, respectively, the highest in Tyskie (5.71 for ²¹⁰Po, 5.06 for ²³⁴U and 6.11 for ²³⁸U) and the lowest in Lech (2.49 for ²¹⁰Po). The effective radiation dose due to uranium and polonium ingestions by beer was calculated and were compared to the effective radiation dose from drinking water. This revised version was published online in July 2006 with corrections to the Cover Date.     

Formation and thermal decomposition of aluminium nitroxy compounds

During the reactions of lithium oxide with aluminium nitride, and of lithium nitride with aluminium oxide, the formation has been observed of a previously unknown compound, of composition Li₂AlNO. The course of its thermal decomposition has also been determined.

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Zusammenfassung Es wurde das Auftreten einer bisher unbekannten Verbindung der Zusammensetzung LiAlNO bei den Reaktionen von Lithiumoxid mit Aluminiumnitrid und Lithiumnitrid mit Aluminiumoxid beobachtet. Der Verlauf der thermischen Zersetzung dieser Verbindung wurde bestimmt.

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Li₂AlNO. .

     

Kinetics and mechanism of base hydrolysis of Reinecke's salt revisited – specific salt effects

The kinetics of base hydrolysis of the trans-[Cr(NH₃)₂(NCS)₄]^– anion follows the rate law: -d[complex]/dt = k ₀ + k ₁[OH^–] (50–70 °C, [OH^–] = 0.1–1.9 M and = 2.0 M). The specific salt effect has been investigated for eight aqueous media: NaCl, NaBr, NaI, NaClO₄, KCl, KBr, CsCl and CsBr. The alkali-independent path (k ₀) does not show any specific effect of inert electrolyte ions, the activation parameters: H = 113.5 ± 0.4 kJ mol^–1 and S = 24.1 ± 1.3 J mol^–1 K^–1 are interpreted in the frame of a dissociative interchange mechanism (I _d). For the alkali-dependent path (k ₁) the specific salt effect is observed for cations of the inert electrolyte, showing an important role for ion-pair formation between the cations and reagent complex anion in the activation process. A linear correlation between lnk ₁ and lnK ₀ (K ₀ – ion-pair formation constant) has been found for the cations studied. The dissociative, via conjugate base, mechanism (D _CB) has been proposed for the alkali-dependent path.     

Stereochemistry of organophosphorus cyclic compounds—II : Stereospecific synthesis of cis- and trans 2-halogeno-2-oxo-4-methyl-1,3,2-dioxaphosphorinans and their chemical transformations

cis- and trans-2-Chloro-2-oxo-4-methyl-1,3,2-dioxaphosphorinans have been obtained by stereospecific reactions of diastereomerically pure 2-methoxy-4-methyl-1,3,2-dioxaphosphorinans or 2-hydrogen-2-oxo-4-methyl-1,3,2-dioxaphosphorinans with chlorine and sulphuryl chloride, respectively. Similarly, the action of the corresponding brominating agents on isomeric phosphites and phosphonates afforded pure cis- and trans-2-bromo-2-oxo-4-methyl-1,3,2-dioxaphosphorinans. It has been shown that halogenolysis proceeds with retention of configuration at the P atom. On the basis of the ¹H- and ³¹P-NMR spectra conformation of the halogenoanhydrides obtained has been discussed briefly.It has been also found that model nucleophilic substitution reactions occur with inversion of configuration at the P atom in the cyclic halogenoanhydrides.     

Novel rhenium(III) complexes with 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine: X-ray structures and DFT calculations for [ReCl3(OPPh3)(dppt)] and [ReCl3(PPh3)(dppt)] complexes

The reaction of [ReOCl₃(PPh₃)₂] with 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine (dppt) has been examined and [ReCl₃(OPPh₃)(dppt)] has been obtained. The triphenylphosphine oxide can be easily replaced by PPh₃ in the reaction of [ReCl₃(OPPh₃)(dppt)] with an excess of triphenylphosphine. The [ReCl₃(OPPh₃)(dppt)] and [ReCl₃(PPh₃)(dppt)] complexes have been structurally and spectroscopically characterized. Their molecular orbital diagrams have been calculated with the density functional theory (DFT) method, and their electronic spectra have been discussed on the basis of time-dependent DFT calculations. The compound [ReCl₃(OPPh₃)(dppt)] has been studied additionally by magnetic measurement. The magnetic behavior is characteristic of mononuclear complexes with d⁴ low-spin octahedral Re(III) complexes (³T_1g ground state) and arise because of the large spin–orbit coupling (ζ = 2500 cm⁻¹), which gives diamagnetic ground state.     

Diffractive proteon fragmentation in 16, 32, and 110 GeV/cK − p interactions and the diffractive production of heavy quarks(s\bar s,c\bar c)

The inclusive proton diffraction dissociation cross sections in 16, 32, and 110 GeV/cK ^? p interactions are determined from the spike nearx=1 in the inclusive negative particle spectra and are compared to those obtained inK?p interactions using other selection methods at various energies. The same procedure is applied to events containing aV ⁰ in order to obtain the cross section for diffractive \(s\bar s\) production. While the total cross section for proton diffraction is found to be approximately constant in the energy range studied here, proton diffraction yielding an \(s\bar s - pair\) is found to increase significantly. In particular it is almost constant at 85 μb forΛ ⁰ and Σ production but for \(NK\bar K\) it rises from zero at 16 GeV.c to about 200 μb at 110 GeV/c. From the result for \(s\bar s\) diffractive production an estimate for the \(c\bar c\) diffractive production cross section of approximately 1–10 μb at 110 GeV/c is obtained.     

Infrared study of adsorption of methanol,deuterated methanol and ethylene on the surface of ZSM-5 type zeolite

The surface species resulting in exposing of the ZSM-5 zeolite at elevated temperatures to methanol, deuterated methanol or ethylene have been studied by IR method.The three-step adsorption at 150°, 300°, 420° C or one-step adsorption at 420° C have been carried out in order to prepare the samples for IR. In all cases the most prominent band appeared in the range 1495–1515 cm^?1; besides two bands at about 1470 and 1370 cm^?1 have been observed. On the basis of Greenler's results and of the shift values of the bands in our spectrum of adsorbed deuterated methanol it was supposed that the band 1495–1515 cm^?1 is due to the OCO group from the surface species. Moreover these species would involve both oxygen atoms from the surface of zeolite but not from OH groups of methanol.     

Influence of MgO (CaO) on the structure of silicate-phosphate glasses

Thermal and structural properties of model silicate-phosphate glasses containing the different amounts of the glass network modifiers, i.e. Mg²⁺ and Ca²⁺ were studied. To explain the changes of the parameters characterizing the glass transition effect (T_g, Δc_p) and the crystallization process (T_c, ΔH) depending on the cations modifiers additions, analysis of the bonds and chemical interactions of atoms in the structure of glasses was used. ³¹P MAS-NMR spectra of SiO₂–P₂O₅–MgO(CaO)–K₂O glasses show that the phosphate complexes are mono- and diphosphate. It has been found that increasing amounts of Mg²⁺ or Ca²⁺ cations in the structure of glasses causes the reduction of the degree of polymerization of the phosphate framework (Q¹→Q⁰). The influence of increasing of modifiers in the structure of silicate- phosphate glasses on the number of non-bridging oxygens per SiO₄ tetrahedron and density of glasses was presented.