The term 'RID OF IMPURITIES' can be broken down into three crossword solutions: PURGE (5 letters), SMELT (5 letters), and FILTERED (8 letters). Purging is a process of removing unwanted or unnecessary items, such as impurities. Smelting is the process of melting ore to separate out the impurities. Finally, filtering is the process of passing a liquid or gas through a filter to remove any impurities. All three processes are used to rid of impurities in various materials.