How can a flame test detect very small amounts of sodium?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A strip of pH paper rests on the rim of a container holding a yellow liquid, with a color comparison chart and several unused pH strips nearby. — chemical analysis Strip of pH paper resting on specimen, with a comparison chart.

A flame test detects sodium by observing the characteristic yellow color produced when the element is excited in a flame. This color is associated with two prominent lines in the yellow portion of the light spectrum.1

To detect very small amounts of sodium, modern analytical methods utilize the intensity of these characteristic spectral lines after excitation by a flame or inductively coupled plasma (ICP). By measuring the intensity of the light emitted at these specific wavelengths, scientists can obtain quantitative measures of sodium concentration, often reaching the parts per million range or lower. While a simple flame test serves as a qualitative indicator, these more advanced photometric techniques allow for the precise determination of trace amounts of the metal in aqueous solutions.2