Alcance
The method is based on passing a solution of the sample in a hydrochloric-hydrofluoric acid mixture through an ion exchange column, removal of all elements other than niobium and tantalum by washing, separation of niobium and tantalum from the resin bed, gravimetric determination of the eluted niobium and tantalum as the pentoxides, if present at high levels. Otherwise coprecipitation with zirconium as cupferrates is used. The elements normally found in nickel alloys do not interfere.