What is colorimetric analysis and how is it used in process measurement?

Colorimetric analysis determines concentration by measuring color intensity produced when sample reacts with specific reagents. Based on Beer-Lambert law: absorbance is proportional to concentration and path length. Online colorimeters automate reagent addition, color development, and measurement at specific wavelength. Applications: chlorine, ammonia, phosphate, silica, and heavy metals in water. Advantages: specific to target analyte, high sensitivity. Considerations: reagent consumption, waste generation, and maintenance requirements for reagent preparation and delivery.