Die Theorie der Alterung eines schwerlöslichen Niederschlags wie AgBr durch Umlösen entsprechend der höheren Löslichkeit von kleinen Teilchen gegenüber derjenigen von großen Teilchen wird quantitativ entwickelt. Es werden Gleichungen für die zeitliche Änderung der Größen‐Verteilungsfunktion, der mittleren Teilchengröße und der Teilchenzahl bei diffusionsbestimmtem und bei reaktionsbestimmtem Stoffübergang mitgeteilt.

The interplay of diffusion processes in metallic and oxide phases during the oxidation of alloys is analyzed theoretically for specified ideal conditions.The oxidation rate of alloys containing a noble metal (Au or Pt) and an oxidizable metal (Ni, Cu, or Zn) is calculated as a function of the alloy composition. The oxidation rate of Ni‐Pt alloys at 850° and 1100°C is essentially determined by the diffusion of nickel to the alloy‐ normalNiO interface if the mole fraction of nickel is less than 0.5. Observed oxidation rates are in accordance with values calculated from diffusion data.Alloys in which both constituents are oxidizable may form either a one‐phase or a two‐phase scale. A necessary but not sufficient condition for the formation of a scale consisting of only one oxide is stated. Results for Cu‐Ni and Cu‐Zn alloys are essentially in accordance with theoretical considerations.On the other hand, it is shown that two oxides may nucleate initially and continue to grow even under conditions under which exclusive formation of the oxide of the less noble metal is a possible process. This is illustrated by observations on Cu‐Al alloys.

Electromotive force measurements on galvanic cells involving solid electrolytes have been made in order to obtain the standard molar free energy of formation of CoO, NiO, Cu~O, AgeS, Ag~Se, PbS, and several phases of the system Ag-Te at elevated temperatures.Haber and Tolloczko (1), Katayama (2), Reinhold (3, 4), Treadwell, Ammann, and Zfirrer (5), Croatto and Bruno (6), Rose, Davis, and Ellingham (7), Sator (8), and others have shown that emf measurements on galvanic cells involving solid electrolytes may yield valuable thermodynamic data. The following investigations have been made in order to show new potentialities of emf measurements on galvanic cells involving solid electrolytes for the determination of the standard molar free energy of formation of oxides, sulfides, selenides, and tellurides at elevated temperatures.

The total electrical conductivity and the electron hole conductivity in solid CuCl, CuBr, and CuI between 250 and 450°C have been determined with help of ac measurements on samples between copper electrodes and dc polarization measurements on the cell Cu|cuprous halide|graphite.

The current distribution at plane electrodes of finite breadth is calculated under the assumption of a linear polarization curve. The current distribution at triangular‐wave profile electrodes is calculated for zero polarization, and an approximate solution is given for high polarization. Results of the theoretical analysis are compared to experimental data reported by Mantzell. It is shown how measurements with the Haring cell can be used to predict current density distributions for other geometrical conditions.

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