Julius Nessler (1827-1905) was a German agricultural chemist who developed a reagent that provides a colorimetric measure of ammonia concentration. A Nessler tube (or cylinder) has a fixed volume and an optically plane bottom, and is suitable for use in a Nessler test. This example is 12 inches long, and marked “EXAX.”
Ref: Arthur H. Thomas, <i>Scientific Apparatus and Reagents</i> (1914), p. 143.