- Julius Neßler
Julius Neßler Born June 6, 1827
Kehl, Grand Duchy of Baden
Died March 19, 1905(aged 77)
Nationality German Alma mater University of Freiburg
Neßler studied at the University of Freiburg from 1853 to 1856, when he attained his PhD. After his Ph.D. Neßler worked for some months with Lambert Heinrich von Babo and Robert Wilhelm Bunsen and then joined a chemical company in Karlsruhe.
A Nessler cylinder  is a simple type of colorimeter. It is best-known for use with Nessler's reagent but can be used for any colorimetric chemical test. In practice, a pair of tubes is used, set on a white background. One tube is filled with color reagent and a known quantity of sample to act as a reference. The sample to be tested is mixed with color reagent in a beaker and the color is allowed to develop. The mixture is then poured, a little at a time, into the second tube until the depth of color in the two tubes is identical. The heights of the liquid columns in the two tubes are measured and the concentration of the sample solution can be calculated using the Beer–Lambert law.
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