EFFECT OF ADDING ALUNITE TO REFRACTORY CLAYS

Four grades of alunite ore were mixed with four grades of fire clays, and the mixtures were formed into modulus of rupture test bars. These were fired to cone 13–14. Specimens were tested for bulk density and modulus of rupture after the initial firing and after reheating to 1400°C. and 1600°C. Softening temperatures of the mixtures were also determined. In general, small quantities (not exceeding 20%) of alunites improved fired characteristics, including decreasing the reheat shrinkage and increasing the P.C.E. The purity of both raw materials was the determining factor. Excessive additions of alunite, particularly to the low-grade clays, caused bloating as a result of the evolution of sulfur gases from the alunite.     

EFFECT OF TIME AND TEMPERATURE ON ACCELERATED CHEMICAL DURABILITY TESTS MADE ON COMMERCIAL GLASS BOTTLES*

Chemical durability results obtained by tests on crushed samples and bottle surfaces on a variety of commercial glass-bottle compositions show the difficulties encountered in attempting to correlate accelerated tests with the actual performance of the bottles toward various solutions under service conditions. The results obtained thus far indicate that the value of accelerated tests conducted with distilled water as a leaching medium is questionable as an aid in predicting resistance of various glass compositions to neutral solutions at room temperature.