The dependence of metal-insulator-metal conductance curves on the chemisorbed ion concentration in the barrier1

The conductance curves of metal-insulator-metal junctions have been found to change in a systematic way with the number of chemisorbed ions in the barrier. Inelastic Electron Tunneling Spectroscopy peak intensity measurements were made on the A1-Pb junctions studied here to determine the number of formate ions chemisorbed on the alumina.     

Bestimmung der Säurestärke der Pentafluoro-orthotellursäure,F5TeOH

The acidity of pentafluoro-orthotelluric acid, F₅TeOH, in glacial acetic acid was determined. Spectrophotometric determination of the over-all dissociation constantK _HX gave the value of pK _HX =9.2. Together with results obtained by other authors for the acidity of mineral acids inAcOH, the following acids can be arranged in order of increasing acidity: $$HNO_3< F_5 TeOH< HCl< TsOH< H_2 SO_4< HBr< HClO_4 .$$ The conductometric titrations allowed the determination, and the proof of the stability of F₅TeOH inAcOH at room temperature. Conductance measurements permitted the qualitative arrangement of F₅TeOH in terms of acidity between HCl and HNO₃. Quantitative evaluation of the conductivity, according toFuoss andKraus, gave erroneous results, since the limiting concentration, where this method is applicable, had to be exceeded for experimental reasons. Measurements with indicators yielded quantitative results. In these experiments, the basicity of the indicators used indicated the same acidity range as for HCl. Spectrophotometric measurements with p-naphtholbenzein as indicator gave the following values: Ionization constantK _i ^IHX =52; Dissociation constantK _d ^IHX =1.6·10^?6; Over-all dissociation constantK _HX =6.9·10^?10. Potentiometric determinations failed, clearly because F₅TeOH reacted with the tetrachloro-quinhydrone indicator electrode.     

Equivalence of topological Markov shifts

We show that any two topological Markov shifts both of whose topological entropy equals logn (for somen) are equivalent by a finitistic coding.