A flame test identifies some metal ions in a solid by the colour they give a flame. Clean a nichrome wire loop by dipping it in dilute hydrochloric acid and holding it in a hot blue Bunsen flame until it gives no colour at all. Then dip the loop in the solid, put it back into the flame, and note the colour.
The colours are: lithium ions Li+ red, sodium ions Na+ yellow, potassium ions K+ lilac, calcium ions Ca2+ orange-red, and copper ions Cu2+ blue-green. The colour comes from the metal ion, not from the negative ion in the compound.
Take care with the results. A blue flame is used so the flame itself adds no colour. Sodium gives a strong yellow that can hide other colours in a mixture, and the red of lithium and the orange-red of calcium are quite similar. Flame tests only work for these metal ions; aluminium and iron ions give no useful colour.
