THE low-temperature chemical alteration of natural glass occurs in two stages: an initial stage in which it remains glassy but absorbs as much as 6 per cent water1, and a final stage in which devitrification to clay minerals, with release of silica, occurs2,3. During the first stage the composition of the glass may change, with gain of K2O and water and loss of Na2O (Smith, R. L., personal communication). This change is due to ion exchange. ?? 1962 Nature Publishing Group.
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Study of natural glasses through their behaviour as membrane electrodes