What is the name of the test used to determine chlorine residual?

The orthotolidine test is a specific method used to measure chlorine residual in water. This test is based on a colorimetric reaction, where orthotolidine reacts with free chlorine to produce a colored compound that can be quantified. By measuring the intensity of the color produced, you can determine the concentration of chlorine residual in the sample.

This method is favored because it provides a relatively quick and straightforward way to assess chlorine levels, which is crucial for ensuring water safety and compliance with regulations regarding disinfection. Monitoring chlorine residual helps ensure that the water remains safe from microbial contamination throughout the distribution system.

Other methods listed, like the colorimetric test, are broader and can refer to various tests that measure different substances, not just chlorine. The pH test specifically measures acidity or alkalinity and does not directly indicate chlorine levels. The chlorination test is not a standard term in this context, further clarifying why the orthotolidine test specifically fits the requirement of measuring chlorine residual.