Styrene emulsion polymerization: Particle-size distributions

Data are presented on the time evolution of particle-size distributions (PSDs) in seeded and ab initio styrene emulsion polymerization systems. Initiation was by chemical reagent (potassium persulfate) or γ-radiation. The unswollen PSDs at various times during interval II of the polymerization were obtained by direct measurement of calibrated electron micrographs. Experimental results were fitted with the equations that describe the time evolution of an initial PSD. Analytic solutions to these equations that allow for entry, exit, and propagation of free radicals were obtained. The values of the rate coefficients for these processes used to fit the experimental data were in excellent agreement with those obtained from dilatometric kinetics experiments.     

Caracterisation physico-chimique de couches minces de polymere obtenues par decharge electrique dans des vapeurs de styrene

Thin polymer layers, obtained by polymerization of styrene vapour in an electrical discharge, are insoluble in solvents for usual polystyrene. However, characterization of the gas discharge polymer, by i.r. spectroscopy, by visible and near u.v. spectroscopy and by chemical microanalyses, show that this material is very near to ordinary polystyrene; this conclusion is further indicated by similarity of the glass transition temperatures of the polymers. However, there are some spectral differences, and an evident reactivity to oxygen and to atmospheric moisture.     

Benzothiazolium derivatives. III. Nucleophilic substitution reactions of benzothiazolium salts

The reactions of 2,3-dihydrothiazolo[2,3-b]benzothiazolium bromide 1 (A^? ?Br^?) with certain nucleophilic reagents have been performed for the purpose of ascertaining the reaction pathways and identifying the group that is displaced from the central carbon atom of the dithiocarbamate system. The nature of complex salt-like intermediates formed initially from 1 (A^? ?Br^?) has been studied and confirmed. For comparison, a number of nucleophilic substitution reactions of 2-methylthio-3-methylbenzothiazolium iodide 17 and 2-dimethylamino-3-methylbenzothiazolium perchlorate 18 have been examined.     

Untersuchung der M?glichkeiten zur indirekten inversvoltammetrischen Bestimmung von Edelmetallspuren

Zusammenfassung Mit Hilfe der indirekten inversvoltammetrischen Methode wurden analytische Bestimmungsmöglichkeiten für die Edelmetalle Hg, Pt, Au und Ag in Verbindung mit Thioharnstoff, Thionalid, 2-Mercaptobenzthiazol und Rubeanwasserstoff untersucht. Während sich für Hg und Ag in jedem Fall gute Bestimmungsmöglichkeiten ergaben, traten für Pt und Au immer dann Schwierigkeiten auf, wenn in alkalischer Lösung gearbeitet werden mußte. Weiterhin werden Möglichkeiten zur einfachen Siliconisierung und luftblasenfreien Füllung der Kemulaelektrode vorgeschlagen.

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Summary Investigations were made in order to find out the analytical possibilities for the determination of the noble metals Hg, Pt, Au and Ag by means of inverse voltammetry of thiourea, thionalide, 2-mercaptobenzothiazole and dithio-oxamide. In each case Hg and Ag can be determined exactly, whereas the determination of Pt and Au in alkaline solutions is difficult. Simple devices for siliconising and air-free filling of the Kemula electrode are proposed.

     

Zur Verwendung von Quecksilber(I)-nitrat als reduktometrisches Reagens

Ohne ZusammenfassungVgl. diese Z. 137, 129 (1952/53); 138, 118 (1953)     

Fragmentierung von α,β-Epoxy-ketoximen zu Acetylenketonen. Vorläufige Mitteilung

A new version of the oxidoketone-alkynone fragmentation is described. Two steroidal α,β-oxido-oximes are shown to fragment to the corresponding alkynones when treated with hydroxylamine-O-sulfonic acid in alcaline solution at room temperature.     

Consequence of boar edible tissue consumption on urinary profiles of nandrolone metabolites. II. Identification and quantification of 19-norsteroids responsible for 19-norandrosterone and 19-noretiocholanolone excretion in human urine

In previous work (Le Bizec et al., Rapid Commun. Mass Spectrom. 2000; 14: 1058), it was demonstrated that a boar meal intake could lead to possible false accusations of abuse of 17beta-nortestosterone in antidoping control. The aim of the present study was to identify and quantify endogenous 19-norsteroids in boar edible tissue at concentrations that can alter the steroid urinary profile in humans, and lead to excretion of 19-norandrosterone (19-NA) and 19-noretiocholanolone (19-NE). The samples were analysed in two laboratories. The methodologies used for extraction and detection (GC/MS(EI) and LC/MS/MS(APCI+)) are compared and discussed. 19-Norandrostenedione (NAED), 17beta- and 17alpha-nortestosterone (bNT, aNT), and 17beta- and 17alpha-testosterone (bT, aT) were quantified. The largest concentrations of NAED and bNT were observed in testicles (83 and 172 microg/kg), liver (17 and 63 microg/kg) and kidney (45 and 38 microg/kg). A correlation between the bNT and NAED content of a typical meal prepared with boar parts and the excreted concentrations of 19-NA and 19-NE in human urine was demonstrated.     

[(C6H5)3P]2Ni(Me3Si?CC?SiMe3). Darstellung,Eigenschaften und Struktur des ersten stabilen Nickel(0)-Komplexes von Bis-trimethylsilylacetylen

[(C₆H₅)₃P]₂Ni(Me₃Si? C?C? SiMe₃). Preparation, Properties, and Structure of the First Stable Nickel(0) Complex with Bis(trimethylsilyl)acetylene The title compound is the first example of a nickel(0) complex with bis(trimethylsilyl)acetylene and obtained from (ph₃P)₂Ni(C₂H₄) and bis(trimethylsilyl)acetylene in tetrahydrofuran. The complex is characterized by some reactions, the i.r. spectrum and by a structural analysis with the aid of X-ray diffraction data. (ph₃P)₂Ni(Me₃Si? C?C? SiMe₃) crystallizes monoclinic in the space group C2/c with four formula units per unit cell (2468 observed, independent reflexions, R = 0.038). The cell dimensions are a = 20.927, b = 13.812, c = 14.238 Å, α = γ = 90°, β = 91.02°. The molecules are monomer in crystalls. The molecule is planar with ligands arranged trigonally about the central atome but distorted to the tetrahedral complex.     

Determination of strontium in human serum by inductively coupled plasma mass spectrometry and neutron activation analysis: A comparison

Strontium has been determined in a human serum reference material by ICP-MS and by NAA. By ICP-MS, results for (88)Sr and (86)Sr in both 10- and 5-fold diluted serum were in good agreement. For (88)Sr the precision was better than 3% and the detection limit was 0.05 mug/l. under the conditions used. The results were 25.5 mug/l. in the liquid serum or 0.281 mug/g in the lyophilized reference material. In the NAA the (87m)Sr produced was radiochemically separated by extraction with oxine in chloroform. The precision was about 10% and the detection limit 0.02-0.05 mug/g.