Flame tests identify the metal ions in a compound (the cations). They change colour when passed through the flame and different ions have specific colours.Li-Crimson ,Na-Yellow , K-Lilac , Ca-Red, Ba-Green
Some reactions form a precipicate when sodium hydroxide is added. The colour of the precipitate formed indicates the metal ion present. Ca, Mg and Al all form white precipiates but Al dissloves when an excess of Na(OH)2 is added. Cu-Blue, Fe(II)-Green, Fe (III)-Brown.