This document discusses colorimetry and its application in trace mineral analysis. Colorimetry is a common analytical technique used in biochemical estimation that involves the quantitative estimation of color. The principle involves how colored substances absorb light in relation to their concentration. Colorimeters measure this using principles like Beer's law and Lambert's law. The document outlines the basic structure of a colorimeter, including its light source, filters, sample cuvette, and detector. It also discusses other analytical techniques like spectrophotometry, atomic absorption spectrophotometry, and flame emission photometry that are used in trace mineral analysis.