Colorimetric refers to a method used to determine the concentration of a substance by measuring the color change that occurs when a chemical reaction takes place. This technique is commonly employed in laboratories to analyze various solutions, where the intensity of the color produced is directly related to the amount of the target substance present. In colorimetric analysis, a sample is mixed with specific reagents that react to form a colored compound. The resulting color is then measured using a device called a spectrophotometer, which quantifies the light absorbed by the solution. This allows scientists to calculate the concentration of the substance based on established calibration curves.