Die Synthese von Calciummetatitanat bei niedriger Temperatur. II Zur Kenntnis der Reaktion zwischen CaC03 und Ti02 in der C02-Atmosphare oder an der Luft

Die Re aktion wurde zwis che n 800 und 1000°C unter sucht. Im Gegen satz zu d en in de r Lite r atur gefund e n e n A n gab en ist es nicht gelunge n die q u a n titative Synthese zu erzielen . F estges t ellt wurde d e r positive Ein fl u s s d er Ca CO a-Dberschusses. Di e C02- -Atmospha re begi.in s tigt b ei a lle n Be ding u ngen e ine besser e Umsetzung des Ti02

Die Synthese von Calciummetatitanat bei niedriger Temperatur. I.

Die Reaktionsfanigkeit des Gemenges Ca(OH)2 und Ca(N03h mit Ti02 wurde eingehend studiert. Fiir ein standardes Ti02 wurde die Abhangigkeit der Ausbeute von der Reaktionsdauer, Temperatur, Dispersitat der Agglomerate, Zusammensetzung und Uberschuss des Ca(OH)2 und Ca(N03)2 Gemenges untersucht. Verglichen wurde die Ausbeute wenn Ca(OH)2 im Gemenge mit Cao ersetzt wird, sowie die Ausbeute bei Reaktionen mit anderen Calciumverbindungen. Auf Grund dieser Untersuchungen kann auf den Einfluss der Schmelze, Atmosphare und Cao in statu nascendi auf den Verlauf dieser Synthese geschlossen werden. Mit geeignetem Ti02 Gel kann man bei 575oc mit einem Gemenge von 1,0 Ti02 + 0,7 Ca(OH)2 + 0,3 Ca(N03)2 bei 1-2 stiindiger Reaktionsdauer praktisch eine 100°/e Ausbeute von Cao . Ti02 erzielen

Uber die Synthese von XeF6

Claassen und Mitarb.1 berlichten iiber die Syinthese von XeF4 , R. Hoppe und Mifarb.2 iiber die Synthese von XeF2 • Wir haiben die Synthese VO!!l XeF43 reproduzii.ert und koomten bei der massenspektrometrischen Analyse des Produktes schwache Andeutungen fiir die .Ainwesenheit hoherer Fluoride feststellen

On the Synthesis of and Magnetic Measurements on Xenon Tetrafluoride

Recently the synthesis of XeF4 was reported from the Argonne Nationlll Laborato·ry, and some of its physical properties were given1• In order to obtalin further information on this extraordinarily interesting compound XeF4 was prepared in our laboratory. Siince the details of the synthesis were not available the direct fluorination was performed under pressure at 400°C. The basic .idea was to obtain the maximum possible amount of the product in a small v.ol\u27l.lllle. The p.roduct was identified by mass spectroscopic analysis2 • The X-ray pattern was taken and the magnetic susceptibility was also measured. At present the NMR spectra are al!so under investigatioiil

Usporedba dinamičke analize para iznad otopine i mikroekstrakcije analita na čvrstoj fazi za plinskokromatografsko određivanje BTEX-a u urinu

The aim of this study was to compare two extraction procedures: dynamic headspace-purge and trap (PT) and headspace solid-phase microextraction (HS-SPME) for gas chromatographic determination of benzene, toluene, ethylbenzene, and isomeric xylenes (BTEX) in urine with photoionization (PID) and mass spectrometric (MS) detection, respectively. Both methods showed linearity in the range of interest [(50-2000) ng L-1], good accuracy (80% to 100 %), and repeatability (RSD≤11 %). Detection limits were in the low ng L-1 level for both methods, although slightly greater sensitivity was found for the PT method. In comparison with PT, HS-SPME was simpler and required less time for analysis. Although the analytical features of both examined methods are appropriate for biomonitoring of environmental exposure to BTEX, only the HS-SPME-GC-MS method is recommended for routine analysis of BTEX in urine. The method was applied for the quantitative analysis of BTEX in urine samples collected from non-smokers (n=10) and smokers (n=10).Cilj ovog rada bio je usporediti dva postupka ekstrakcije za plinskokromatografsko određivanje benzena, toluena, etilbenzena i izomera ksilena u urinu. Uspoređene su dinamička analiza para iznad otopine (tzv. purge and trap) uz fotoionizacijski detektor i mikroekstrakcija analita na čvrstoj fazi uz detektor spektrometar masa. Rezultati upućuju na linearnost odziva detektora u ispitivanome koncentracijskom području [(50- 2000) ng L-1], zadovoljavajuću točnost (80 %-100 %) i ponovljivost (RSD ≤11 %). Postignute su niske granice detekcije za obje metode. Mikroekstrakcija analita na čvrstoj fazi uz detektor spektrometar masa pokazala se jednostavnijom i bržom za izvođenje pa se preporučuje za rutinsko određivanje BTEX-a u urinu. Metoda je primijenjena za analizu tih spojeva u uzorcima urina nepušača (n=10) i pušača (n=10)

10.34: Creep properties of grade S275JR steel at high temperature

The paper describes an ongoing research project which aims to determine the creep properties of European steel Grade 275JR. The purpose of the research is to develop a reliable temperature‐, stress‐ and time‐dependent creep model for this alloy, since there is very little information available in the scientific community regarding its creep properties. The research within the project is focused on a series of stationary creep tests, which will be used to obtain time‐dependent creep strains in the temperature range 400–600°C. The stress range for which the creep evolution is studied in this project is between 25% and 90% of the value of the stress at 0.2% strain at any particular temperature level. Comparisons between the creep output for the alloy analysed and existing creep data are presented in the paper