Carl Wagner

The Mechanism of the Decomposition of Nitrous Oxide on Zinc Oxide as Catalyst

For the decomposition of nitrous oxide on metals and oxides, a tentative mechanism is indicated which involves quasi‐free electrons as reactants and adsorbed oxygen ions as intermediate product. This mechanism is in accordance with experimental facts such as retardation by oxygen, a fractional order of the reaction with respect to nitrous oxide in the case of indium oxide as catalyst, and the decrease of the electrical conductivity of zinc oxide due to the presence of nitrous oxide. A mixture of zinc oxide and gallium oxide, however, has about the same catalytic activity as pure zinc oxide, although the electrical conductivity of the mixed catalyst is about fifty times greater than that of pure zinc oxide. This finding can be accounted for by the assumption that the reaction between nitrous oxide and electrons of the catalyst takes place in the vicinity of an adsorbed zinc ion or an anion vacancy.

Solubility Relations in Ternary Solid Solutions of Ionic Compounds

The variation of the solubility of a solute due to the presence of a second solute in a solid ionic compound as solvent is investigated theoretically with the aid of the ideal law of mass action. Ions of the solvent in interstitial positions, cation and anion vacancies, quasi‐free electrons, and electron holes are to be taken into account in the same manner as the constituents of conventional chemical systems. The theoretical conclusions are illustrated by experimental data, however, qualitatively rather than quantitatively. The solubility of lead chloride in solidsilver chloride is decreased by presence of cadmium chloride. The solubility of iodine (or cupric iodide) in cuprous iodide is likewise decreased by presence of cadmium iodide. The behavior of the corresponding bromide system is analogous. Conversely, gallium oxide increases the solubility of zinc in zinc oxide. The phenomena to be expected in lead sulfide as solvent are more complicated, since this substance can dissolve both excessive lead and excessive sulfur. The oxidation rate of nickel is increased by presence of chromium and manganese, whereas the chlorination rate of silver is decreased by presence of lead and cadmium chloride.

Diffusion of Lead Chloride Dissolved in Solid Silver Chloride

A particular solution of the differential equation of diffusion involving a diffusion coefficient proportional to concentration is presented.From previous experiments by Wagner and Zimens the diffusion coefficient for the exchange of lead and silver ions, extrapolated to the concentration of a saturated solution of lead chloride in solid silver chloride, is calculated to be 2.4·10−9 cm2/sec. at 270°C. Therefrom it follows that the self‐diffusion coefficient of lead ions equals 0.8·10−9 cm2/sec. In contrast, the self‐diffusion coefficient of silver ions, derived from conductivity measurements of Koch and Wagner, amounts to 9.2·10−8 cm2/sec.

Determination of the Concentrations of Cation and Anion Vacancies in Solid Potassium Chloride

The mobility of cation vacancies and the equilibrium concentration of cation and anion vacancies in solid potassium chloride are calculated from measurements of the electrical conductivity of pure potassium chloride and solid solutions of strontium chloride in potassium chloride.

Transference Numbers of Solid Potassium Chloride with Strontium Chloride, Potassium Oxide, and Sodium Sulfide as Additives

The transference number of cations in solid potassium chloride at 600°C has been found to be 0.88 in accordance with previous experiments of Tubandt, Reinhold, and Liebold. Addition of strontium chloride causes increase of the transference number approaching unity. Addition of potassium oxide and sodium sulfide, respectively, lowers somewhat the transference number of cations and accordingly increases the transference number of anions. These results are in accordance with the Schottky disorder model, but the presence of interstitial cations apart from cation and anion vacancies cannot be ruled out.

Über einen einfachen Sonderfall zur Berechnung der Temperaturverteilung in Wärmespeichern beim Wärmeaustausch mit strömenden Gasen

ZusammenfassungFür die Temperaturverteilung in einem festen Körper (Wärmespeicher) bei Aufheizung durch einen erhitzten Gasstrom wird eine geschlossene Lösung unter folgenden Voraussetzungen mitgeteilt: Vernachlässigung der Wärmeleitung parallel zur Gasströmungsrichtung im Gas und im festen Körper; Wärmeleitung senkrecht zur Gasströmungsrichtung im festen Körper endlich und damit wesentlich bestimmend, im Gas unendlich groß (also auch Wärmeübergangszahl unendlich groß); unendliche Ausdehnung des festen Körpers senkrecht zur Gasströmungsrichtung.

Wärmeleitungsprobleme für Systeme mit beheizten Rohren und Hohlkugeln in einer unendlich ausgedehnten Umgebung

ZusammenfassungEs werden Gleichungen für die Temperaturverteilungen in einem unendlich ausgedehnten Medium mit beheiztem Hohlzylinder sowie mit beheizter Hohlkugel mitgeteilt. Im besonderen wird der Wärmefluü je Flächeneinheit berechnet, wenn eine bestimmte übertemperatur gegenüber dem gleichförmig vorausgesetzten Anfangszustand an der Wand des Hohlzylinders bzw. der Hohlkugel vorgegeben wird. Ferner wird die übertemperatur berechnet, wenn der Wärmefluü je Flächeneinheit an der Wand des Hohlzylinders bzw. der Hohlkugel vorgegeben wird. Für die beim Hohlzylinder auftretenden Integrale von Besselfunktionen werden Interpolationsformeln und graphische Darstellungen gegeben. Die Lösungen für die Hohlkugel werden in geschlossener Form erhalten.