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Thermodynamic calculations are provided for equilibrium in the system Ag − O 2 . Kinetics of hightemperature (up to 900°C) oxidation in air of plates made from pure silver (99.99 mass% Ag) and jewellery alloy 84 at.% Ag − 16 at.% Cu are studied by nonisothermal thermogravimetry, and differential and petrographic analyses of the reaction products. Mechanisms are established for the corresponding oxidation reactions confirming the absence of chemical reaction for pure silver with oxygen at T > 422 K. The Wagner theory for oxidation of alloys containing precious metals is confirmed by the results. The temperature ranges are determined for van de Waals adsorption and chemisorption of oxygen at the surface of very pure silver powder with a specific surface area S = 0.4 m 2 /g.The properties of silver, including some data relating to its oxidation, in particular at high pressure, have been aired in a review [1], and in a monograph [2]. In dry air at room temperature silver is coated with a layer of oxide whose thickness does not exceed 100 nm. At 200°C the layer of oxide is somewhat thicker, at 300°C and a pressure of 2 MPa oxidation may be complete [2]. In order to measure the small thickness of the Ag 2 O layer Davies [3] used an electrometric method. Benton and Drake [4] studied silver oxidation kinetics at 168°C and different oxygen pressures. They established that the rate of oxide formation is directly proportional to oxygen pressure, and the activation energy in the range 100-170°C is 92.2 kJ/mole. Menzel and Menzel-Kopp [5] carried out a crystallographic study of the Ag 2 O layer obtained on a silver single crystal at 900°C and a pressure of 10 MPa; in these case oxidation occurs through a process of nucleus formation. Watanabe [2] studied single-crystal silver, heated in oxygen, by an electron diffraction method; in ozone oxidation is only possible in the presence of moisture. Dankov and co-authors [6] showed that the Ag 2 O oxide lattice obtained at a silver anode is deformed.The aim of this work is to study oxidation features in air for a plates of pure silver (99.99 mass% Ag) and jewellery alloy 84 at.% Ag − 16 at.% Cu up to 900°C, and also the mechanism of desoprtion-adsorption of oxygen at the surface of Ag (99.99 mass%) powder on heating it in an air up to 900°C. High-temperature oxidation of both compacted specimens was studied by thermogravimetry (TG) and differential thermal analysis (DTA) in a Q-1500 derivatograph in a nonisothermal regime with a rate of change in temperature of 10 deg/min. In order to determine the composition of oxidation products for Ag − Cu jewellery alloy at different stages of oxidation (at 650, 750 and 900°C) more prolonged (180 min) isothermal oxidation was performed in the same device. Oxide layers that formed on the plates were removed in the form of powder particles with a scalpel and analyzed in a mineralogical microscope MIN-8 using standard liquids with a known refractive index (petrographic analysis).The specific surface area of high purity silver powder was determined...