Estudos sobre as propriedades químicas dos Minerais de Zirconio da Região de Poços de Caldas — Minas Gerais

Abstract

Zircon and baddeleyite from the region of Poços de Caldas were reexamined as to their chemical properties, special attention being dedicated to the hafnium content. This was found to be low, of the order of 1,8% of the total zirconia and hafnia present. The differences in hafnium content of diverse samples are larger than the probable experimental error. Fractionation of zirconium and hafnium is easily accomplished by precipitation of phosphates in presence of large excess of sodium sulfate or bisulfate. Precipitates thus obtained are well flocculated, easily filtered, free from iron and titanium, and contain the larger fraction of the hafnia, while zirconia nearly free from hafnia remains in solution. With only a few fractional precipitations, a solution of zirconia completely free from hafnia can be obtained. By analysis of the pyrophosphates prepared from the fraction richer in hafnium by precipitation with sodium pyrophosphate in hydrochloric acid solution, a good approximation to the total hafnia content of the samples can be found