A technique analogous to emission spectrometry, but using a flame to excite electrons, rather than an arc or plasma. It is a simple and straightforward analytical technique that is basically a quantitative version of a ‘flame test’. A known weight of sample is dissolved in hydrofluoric acid and either perchloric or sulphuric acids, portions of the solution are added to a flame, and the strength of emission of light of a particular wavelength produced by the potassium in the flame is recorded. This is then compared with those produced by standard solutions. The final results may be affected by sodium concentrations as well as by the sulphuric acid. Perchloric acid, iron, magnesium, aluminium, and calcium also interfere with the potassium emission but their effects may be reduced by buffering and by the removal of interfering ions.