Nessler cylinder
Nessler cylinders are laboratory tubes with a fixed volume, made of glass with optically plane bottom. On the walls, there are marks of the nominal stroke volume and possibly one halfway mark.
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. Basically, there are four types of used cylinders:
- high with a capacity of 50 ml
- low with a capacity of 50 ml
- high with a capacity of 100 ml
- low capacity of 100 ml
Hehner cylinders differ in that they are scaled to full height.
Due to the spread of automated spectrophotometers, colorimetric assay methods using Nessler cylinders and visual assessment are used very rarely. However, Nessler cylinders are still used as reaction vessels, in the same way as test tubes.