ABSTRACT
This chapter concerned with impurities in the metal that are harmful and need to be removed. The impurities in a metal can be nonmetallics as well as metallics. In a refining process we are generally concerned with removal of one or more constituents from a metal that contains a number of impurities. After the extraction of metals from their primary or secondary sources, purification and consolidation are the final steps required before the metal can be used in various industrial applications. Reduced metal is generally not pure enough for use in most applications. The nonmetallic impurities are mainly picked up from the reaction environment. Reduced niobium metal can be refined to commercial-grade metal or to a state of high purity by using one or a combination of refining techniques. Niobium metal can be readily refined by heating it under high vacuum conditions up to or above its melting temperature.
