VANADIUM AND MOLYBDENUM COMPOUNDS IN CLAYS1

Eight different light-firing clays and shales containing small amounts of insoluble vanadium and molybdenum compounds were studied. It was found that during firing, soluble salts of these elements were formed which later appeared as a green-yellow efflorescence on the fired clay. The color of the efflorescence was chiefly due to alkali vanadates. It was found that the use of either sodium fluosilicate or calcium fluoride is effective in eliminating the green-yellow efflorescence. The use of these chemicals is usually a more economical procedure than either hard firing or the use of lead compounds. The results of various trial firings made with clays to which were added varying amounts of several different chemicals are given.     

PROGRESS REPORT ON INVESTIGATION OF FIRECLAY BRICK AND THE CLAYS USED IN THEIR PREPARATION1

This is a progress report of an extensive study of fire clays and fireclay brick. It includes the results of a preliminary study of clays representative of those used in the manufacture of refractories throughout the United States. Chemical analyses and a summary of physical tests are given of both fire clays and the brick manufactured from them. The thermal expansion behavior of the fire clays fired at 1400°C and those of the fire brick “as received” from the manufacturer and also after firing at 1400°C, 1500°C, and 1600°C were studied and the materials classified into groups having characteristic thermal expansions. The moduli of elasticity and rupture were determined at 20°C, 550°C, and 1000°C. The resistance of the brick to spalling in a water-quenching test is expressed in an empirical relation correlating the elasticity, strength, coefficient of expansion, and percentage of grog used in compounding the brick batches. Data are presented on individual bricks made by the same manufacturer showing probable reasons for great differences in the number of quenchings required to cause spalling in the water-dip test.     

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