Copper metal flame test: a clean nichrome wire is dipped into a copper salt solution (eg copper sulphate) and the wire introduced into the bunsen flame, which glows with a characteristic green flame. The flame is coloured due to the fact that the salt is vapourised by the flame and excited to emit radiations that are characteristic for that particular metal. The same phenomenon provides the basis for flame photometry, where intensity of emission indicates concentration of a particular metal in solution.