Die flammenphotometrische Analyse (Atomabsorption) der Elemente Na, K, Mg, Mn und Ca im Zement

Ohne Zusammenfassung     

Condensation of gases on metals: The one-dimensional square well model

Trapping probabilities of gas atoms at surfaces are calculated assuming a classical onedimensional square well potential as a function of gas and surface temperatures. It is shown that initial sticking coefficients of chemisorbed gases on transition metal surfaces can in most cases be fit fairly well by this model using reasonable values of the interaction energy, although the model does not predict observed behavior for surface temperatures>600°K. For some systems the initial sticking coefficients are higher than predicted by this model, indicating that other mechanisms of energy transfer are probably operative. The angular dependent sticking coefficient which would be measured in a molecular beam experiment is also computed.     

Beiträge zum chemischen Transport oxidischer Metallverbindungen. VI. Über die Keimbildung im System NiFe2O4/HCl/Quarz

Contributions to the Chemical Transport of Metal Oxides. VI. On the Nucleus Formation in the System NiFe₂O₄/HCl/Quartz The validity of the reaction equation of the chemical transport reaction was proved and confirmed experimentally in connection with thermodynamical data by segregation of NiCl₂ from the gaseous phase within the temperature range of 750 to 900°C and the pressure range of 0,9 to 5,5 atm. After that the times t from the beginning of the temperature difference to the formation of the first nucleus in dependence on the temperature difference ΔT were measured in the system NiFe₂O₄/HCl/quartz for the temperature range 900 to 1100°C and the pressure range of 0,07 to 6,3 atm. The measured values obey a linear relation lg t/1/ΔT, which was explained by derivation of an analogous relation from the Volmer equation accepting two-dimensional nucleus formation. The slopes of the straight lines decrease with increasing temperature. The proportionality of the slope and of the free energy of nucleus formation permits to explain this observation with the Pound model, after which the surface diffusion plays an important role in the formation of heterogenous nucleus. From the slope of the straight lines the free energies of the nucleus formation for a supersaturation of 50 percent were estimated to (5 to 15) · 10^?13 erg/nucleus in the temperature range 900 to 1100°C. From this follow diameters of nucleus of 15 to 7 Å.     

Mass spectroscopy of natural products. V—Mass spectroscopic studies of ring a substituted allobetulane derivatives

The mass spectrometric behaviour of ring A substituted allobetulane derivatives is discussed. The position and nature of a substituent both influence the mass spectral decomposition remarkably. In the case of the epimeric 1-hydroxy- and acetoxy allobetulanes, the mass spectral differences are great enough to distinguish these from each other. The results should yield a general rationalization for other saturated triterpenes having the same A, B, C ring system.     

Coulomb excitation studies of 160Dy, 162Dy and 164Dy

Coulomb excitation measurements with ¹⁶O and ⁴He projectiles have been performed on ¹⁶⁰Dy, ¹⁶²Dy, and ¹⁶⁴Dy. The ground-state rotational bands up through the 8⁺ member were observed in the ¹⁶O experiments. The measured excitation probabilities yield B(E2; I → I ?2) values which are generally in agreement with the rotational predictions except for the 6⁺ → 4⁺ values. In each nucleus, probabilities for exciting the 2⁺, 4⁺, and 6⁺ members of the γ-vibrational band were measured and compared with calculated results. The B (E2; 0⁺ → 2⁺γ) values were measured in experiments involving ⁴He ions. The K^π = 2^? octupole band was observed in each nucleus in addition to 1^? bands in ¹⁶⁰Dy and ¹⁶²Dy. Excitation probabilities were analyzed in an attempt to extract B(E3) values.