A typical analysis program in the Model CA-6 Colorimetric Chlorine Analyzer would have the following structure: Rinse the colorimetric reaction cell with the sample solution and take a sample, add one or more reagents (buffer or masking agent), and then make the first measurement, called the Reference measurement. The Reference measurement eliminates interfering factors such as sample color and turbidity, as well as miscellaneous color from the reagents and refractive index variations.
After the Reference reading, the color producing reagent(s) are added. The sample is mixed and allowed time to complete the color forming reactions before taking the second measurement, the Reading measurement. The Reference and Reading values are used to calculate the end result. The reaction cell is then drained and rinsed several times before starting the next measurement.