Misconceptions and Insights about Flame Tests

Flame tests, in which aqueous metal salt solutions on a wire inserted into a flame produce colored emissions, are one of the simplest demonstrations used in chemistry. Unfortunately, the phenomena giving rise to the colored emissions is poorly understood by many and often described incorrectly in textbooks and published articles. In the present commentary, the details of flame tests are discussed in the context of well-established atomic spectroscopy. It is shown that the emission does not come from the ions which are present in solution but rather usually comes from the excited states of the corresponding neutral atoms. Details of the mechanism, involving ion desolvation and gas-phase electron transfer, are discussed.