Die elektroanalytischen Schnellmethoden

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Zur Titerstellung des Kaliumpermanganats

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Ueber die F?llung und Bestimmung des Mangans durch Anwendung von Schwefelammonium

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Bestimmung des Jod's in organischen Verbindungen

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Neue Literatur

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Low frequency acoustic and dielectric measurements on glasses

The acoustic and dielectric properties of different glasses at audio frequencies and temperatures below 1 K have been investigated with the vibrating reed and a capacitance bridge technique. We found the temperature dependence of the absorption of vitreous silica (Suprasil W) to agree with the predictions of the tunneling model which is commonly used to explain the low temperature behaviour of amorphous materials. The variation of the sound velocity and of the dielectric constant, however, shows significant deviations from the expected behaviour which cannot be accounted for by a simple modification of the model. Instead, it seems to be necessary to introduce a temperature dependence of some relevant model parameters. Moreover, at very low temperatures (T < 0.1 K) the sound velocity strongly depends on the excitation levels. The absence of this effect at higher temperatures proves that it can be ascribed to a nonlinear response of tunneling systems. Similar results were found in sound velocity measurements on a cover glass and on a superconducting metallic glass (Pd₃₀Zr₇₀, T_c = 2.6 K), which indicates that these features are a general aspect of the dynamics of tunneling states in glasses. In contrast to the insulating glasses we found that in Pd₃₀Zr₇₀ also the internal friction is strain dependent.     

Elektrolytische Bestimmungen und Trennungen

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Surface self-diffusion of quench condensed hydrogen films

The annealing behaviour of quench condensed H₂-, HD- and D₂-films has been investigated using acoustic surface waves. Upon annealing at temperatures far below the triple point we observe drastic changes of sound velocity and attenuation which can be attributed to a considerable rearrangement of the film structure via surface diffusion. These findings are in good agreement with recent experiments using surface plasmons. From the temperature dependence of the speed of the structural changes we deduce the activation energies for surface self-diffusion as 23 K, 35 K, and 47 K for H₂, HD, and D₂, respectively.     

Bestimmung von 2,8-Dihydroxyadenin im Harn mit der HPLC

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Determination of urinary 2,8-dihydroxyadenine by HPLC