This document specifies a) a method for determining the hydrolytic resistance of glass grains at 98 �C. The resistance is measured and expressed by the volume of acid required for titration of the alkali extracted from the unit mass of glass, and can also be expressed by the amount of sodium oxide equivalent to this volume of acid, and b) a classification of glass according to the hydrolytic resistance determined by the method of this document. This document is intended for use on the less resistant types of glass, such as soda-lime glass.