Method for the separation of niobium and tantalum

Claim 1

IN A PROCESS OF SEPARATING NIOBIUM FROM TANTALUM PRESENT IN A STARTING MATERIAL CONTAINING THE PENTOXIDES OF SAID METALS, BY REDUCING THE STARTING MATERIAL BY MEANS OF A REDUCING AGENT SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND CARBON MONOXIDE IN AN AMOUNT INSUFFICIENT TO CAUSE REDUCTION TO THE METALLIC STATE BUT SUFFICIENT TO REDUCE THE MAJOR PART OF THE NIOBIUM PENTOXIDE PRESENT IN THE STARTING MATERIAL TO NIOBIUM DIOXIDE WHILE THE MAJOR PART OF THE TANTALUM PENTOXIDE REMAINS IN THE UNREDUCED, STATE AS TANTALUM PENTOXIDE, THE STEP OF EXTRACTING THE RESULTING PARTLY REDUCED STARTING MATERIAL WITH CONCENTRATED SULFURIC ACID AT ABOUT 200* C. UNTIL SUBSTANTIALLY ALL THE DIOXIDE CONTENT PRESENT IN SAID PARTLY REDUCED STARTING MATERIAL IS DISSOLVED, SEPARATING, BY FILTRATION, THE RESULTING SOLUTION FROM THE UNDISSOLVED RESIDE CONTAINING THE MAJOR PART OF THE TANTALUM PENTOXIDE PRESENT IN THE STARTING MATERIAL, AND PRECIPITATING A PRODUCT OF A HIGH NIOBIUM CONTENT FROM THE RESULTING ACID SOLUTION.