Vapor Pressures of Simple Silicate Glass Melts

Partial and total vapor pressures over Na2O.3SiO2 anhd Rb2O.3SiOz melts were determined at 1150° to 1300°C with the Knudsen-effusion method. A Pt Knudsen cell was placed on a microbalance so that the weight loss due to effusion from the Knudsen hole could be recorded continuously. The specific vaporization rates are between ∼3.10−6 and 3.10−4 gcm−2 s−1; the corresponding vapor pressures are between ∼3.10−2 and 3 Pa.