PROPERTIES OF NATURAL ALUNITIC CLAYS

The mineral and chemical compositions and some of the refractory and firing properties of eight alunite‐bearing clays were investigated. It was found that alunite raises the softening temperature of clays. Secondary expansion occurs in reheating the clays at temperatures higher than the original fir...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 1946-11, Vol.29 (11), p.308-313
Main Authors: Knfžek, Jan O., Fetter, Hans
Format: Article
Language:English
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Summary:The mineral and chemical compositions and some of the refractory and firing properties of eight alunite‐bearing clays were investigated. It was found that alunite raises the softening temperature of clays. Secondary expansion occurs in reheating the clays at temperatures higher than the original firing temperature and the degree of expansion seems to depend uot only on the alunite concentration in the clay but also on its characteristics. This expansion is believed to be due to SO2 or/and SO2 gases released by the body in refiring; these gases expand at high temperature causing bloating of the body. The usefulness of thermal analysis in detecting small amounts of alunite is pointed out.
ISSN:0002-7820
1551-2916
DOI:10.1111/j.1151-2916.1946.tb11603.x