Action of diatoms on clay

With the recent trend toward the use of higher temperatures and more severe service conditions in the metallurgical and refractories industries there has developed a constantly greater demand for high-alumina clays, that is, clays in which the alumina content is considerably above that of pure kaolinite, Al₂O₃2SiO₂·H₂O. However, the known reserves of good diaspors are so small that ceramic engineers are already turning to basic refractories in order to have sufficient materials for work at high temperatures. Even the slightest reflection on the needs of the refractories industry will show that such substitutions are strictly limited, and possible only where the new material does not introduce further complications and difficulties. Since 1891 it has been known that diatoms can decompose clay to obtain the silica for their frustules. Recent research in the Academy of Science of the USSR has elucidated some of the finer points of this action of diatoms, but as the work was done in pure culture, and in minute quantities, there remains the question, can diatoms be induced to grow on a large enough scale so that man can use them to raise the alumina content of clays? In the conviction that in the near future there will be a demand for high-alumina clays greater than the supply, this study was undertaken in order to learn whether an industrially practical process could be worked out, and if not, at least some further addition to knowledge could be made --Introduction, page 1