Nessler cylinders are used for colorimetric analysis, such as APHA color.
The color of the substance contained in a Nessler cylinder is visually compared with the model.
The tubes often carry out a series of calibrations of solutions of increasing concentrations, which functions as a comparative scale.
To minimize differences in the subjective impression of the color of the solution of the substance to be analyzed, cylinders of a series should have the same characteristics - height, diameter, and thickness of glass.
Due to the spread of automated spectrophotometers, colorimetric assay methods using Nessler cylinders and visual assessment are used very rarely.