Variations Caused in Heating Curves of Glass by Heat Treatment (Classic Reprint)

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Excerpt from Variations Caused in Heating Curves of Glass by Heat TreatmentThe exothermic eflect occurs when a chil led glass is heated because this glass while being heated through the lower part of the temperature range of this effect is, from a physicochemical standpoint, in a series of very unstable conditions which correspond more nearly to the equilibria which are attainable at temper atu1 es above the point where the curve maximum occurs than they do to those equilibrium condi tions which the glass 1s Oapp1oaching so long as it is in the tempera ture rang e belowo the point of this curve maximum.In theg consideration or these unstable conditions it is desirable to select some characteristic of a glass in a given condition that will differentiate that condition more or less definitely from all other conditions in which the glass may exist at the same actual tempera ture. A theoretical temperature corresponding to that equilibrium condition which most closely resembles the given condition 1s suitable for this purpose, since the glass assumes these unstable conditions because the chilling treatment produced an under cooling, the excep tional magnitude of which may be visualized in this way, that is, this equilibrium temperature in falling during the chilling treatment (see curves A' and B', fig. 1 (b) lagged farther and farther behind the acutal temperature of the glass as the cooling progressed and became practically stationary much sooner (relatively speaking) than the latter and at a point which was well above the usual annealing range where equilib1ium conditions are normally approximated as a result of ordinai y annealing treatments.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.