What Are Some Uses for Flame Tests?

Flame tests help miners, geologists, chemists and other related professionals identify the presence of chemical elements in a sample using the element’s emission spectrum. Metal ions emit a specific color when heated, which identifies them in the sample. Flame tests cannot detect all elements, and the test only indicates the presence of an element, not its concentration.

Flame tests use simple equipment, making them ideal for fieldwork. Geologists use the flame test to identify the presence of metals. Forensic scientists can use flame tests at crime scenes for quick analysis of elements present. Miners use the test for analysis of samples, particularly when prospecting. Flame tests provide a good teaching tool for chemistry students learning about emission spectra.

Unlike more sophisticated spectrographic equipment, a flame test requires only a gas burner, a hydrochloric acid solution and nichrome wire to hold the sample. The process is simple: dip the nichrome wire in the acid solution and hold it in the flame to remove any impurities, then affix the sample and hold it in the flame. The emitted colors show what metal ions the sample contains. For example, Copper emits a deep blue, Sodium bright orange and Lead a grey-white color. A table of elements and their characteristic colors helps with identification.

The flame test has limits, though. The flame emits its own color, and that can interfere with some spectrum colors, notably orange. Sometimes a filter of cobalt blue glass helps testers identify the various shades of orange. Concentrations cannot be identified, and the test results depend on sample size and repeated testing to improve accuracy.