Prüffmittel
Prüffmittel is a term used in German-speaking laboratories and industry to denote materials and substances employed to perform tests, verify results, or demonstrate properties of a sample. Prüffmittel encompass chemical reagents such as acids, bases, solvents, indicators and other substances of defined purity; calibration standards and reference materials used to calibrate instruments or validate methods; as well as control samples, test kits and measurement artefacts designed to check accuracy and precision. They are selected according to the analytical method and the required quality grade (for example Analytical Reagent AR or ACS grade in chemistry). They may be chemical reagents, physical standards (weights, gauges) or semi-physical tools such as test strips or pH papers, depending on the field.
In practice, Prüffmittel serve several purposes: to initiate a reaction or signaling response in qualitative tests;