NesslerVerfahren

The NesslerVerfahren, often referred to as Nessler's reagent, is a chemical test used for the detection and quantification of ammonia or ammonium ions. Developed by Julius Nessler in the late 19th century, it is a colorimetric method. The reagent itself is an alkaline solution of potassium tetraiodomercurate(II), with the chemical formula K2[HgI4].

When ammonia is present, Nessler's reagent reacts with it to form a distinct yellow to brown colloidal suspension or solution. The intensity of the color produced is directly proportional to the concentration of ammonia. This color change allows for both qualitative detection (presence or absence of ammonia) and quantitative analysis through comparison with standards or using a spectrophotometer.

The NesslerVerfahren is commonly employed in various fields, including environmental monitoring for water quality analysis, in agricultural laboratories to measure ammonia content in soil and fertilizers, and in biochemical research. While a sensitive test, it can be subject to interference from other substances, such as amines and certain sulfur compounds, which can also produce coloration or turbidity. Careful sample preparation and controlled conditions are therefore important for accurate results. Despite the development of newer analytical techniques, Nessler's reagent remains a useful and accessible method for ammonia determination in many applications.