Spectrography

A very accurate method for quantitative analysis of small samples of various compounds. It depends on the fact that light emitted by any element shows a characteristic pattern when split by a prism into its spectrum, as sunlight is split in a rainbow. In a compound or mixture, the elements present can be identified by the lines in the resulting spectrum, and measured by the intensity of the lines in comparison with control spectra of known composition produced under the same conditions. The small sample needed, less than 10 milligrams, makes the method particularly suitable for unexpendable archaeological material. The resulting light refracted onto a viewing screen or photographic plate, where its information can be recorded. The method has been used especially for metal analysis, giving useful information on technology and sources of raw materials. Other applications are in the analysis of glass, faience, pottery and obsidian.