Occurrence of Vanadium and Molybdenum in Clays

Abstract

THE occurrence of vanadium in clays has been known for some time, the amounts varying from a chemical trace to about 14 per cent^1,2,4. Mellor devised a method for determining vanadium in the presence of titanium, but the surest test is a spectrographic one. Generally the percentage is less than 1 per cent and it is not known in what form it occurs. Callister¹ in Australia noted that vanadium compounds in kaolins are not water-soluble until the clay has been heated to temperatures of above a 1,000° C. I have found similar properties in South African clays. Many fire and building bricks made from clays of Karroo age exhibit a greenish-yellow or canary-yellow efflorescence, after weathering. The efflorescence is readily soluble in hot water. This efflorescence contains vanadium and molybdenum. Molybdenum is a much rarer constituent and is not easily detected in clays, by ordinary methods. In fact the only method appears to be, to heat large lumps of the material to temperatures of about 1,000° C. and then to extract with hot water and crystallize the salts in solution.