The determination of the origin of a bubble from its gaseous content is complicated by the interaction between the bubble and the melt. In order to study the interaction between bubbles and melt, a molten soda-lime silica glass has been bubbled with air, nitrogen, oxygen, carbon dioxide, argon and sulfur dioxide at 1470°C. The residual bubbles are characterized by a low pressure, heavy -sulfur/sulfate deposits and very similar compositions (N_2 + CO_2). In particular, bubbling with oxygen produces bubbles with constant P_(N_2) and P_(CO_2) indicating that an equilibrium is reached.The presence of deposits of sulfate and/or sulfur, often observed on the bubble wall, may be related to the near saturation of the glass with SO_2 when melted with sulfate and carbon. By analogy the whole bubble evolution may be attributed to the same phenomenon : the tendancy towards equilibrium between the bubbles and the gas partial pressure of the glass melt which leads to a considerable modification of the gas content.It seems probable that the partial pressures in the melt are related to the melting conditions and the degree of fining of the glass, information which could be obtained through oxygen bubbling in a reduced glass containing sulfate.Information about the origin or history of bubbles is probably contained in the difference between the equilibrium gaseous composition and their actual content : time and temperature of residence in the glass melt have certainly a great influence the degree of evolution toward equilibrium.
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