Nessler method
The Nessler's method (according to the namesake actually Nessler method ) is a method for the detection of ammonia in the ambient air. It is a manual process.
Structure, procedure and use
When sampling, the air to be examined is passed through an absorption vessel containing dilute sulfuric acid . The ammonia contained reacts with the sulfuric acid to form ammonium sulphate . This is followed by a chemical reaction with Neßler's reagent , so that a yellow-brown colloid is formed, the color intensity of which can be measured photometrically .
The relative detection limit is between 2.5 µg / m 3 and 50 µg / m 3, depending on the absorption vessel . The process is not selective for ammonia and has cross-sensitivities to amines .
A VDI guideline from 1976 on immission measurement of ammonia concentration using the Nessler method was withdrawn in January 2009.
literature
- VDI 2461 sheet 2: 1976-05 measurement of gaseous immissions; Measuring ammonia concentration; NESSLER method. VDI publishing house, Düsseldorf.
Individual evidence
- ^ A b Franz Joseph Dreyhaupt (Ed.): VDI-Lexikon Umwelttechnik. VDI-Verlag Düsseldorf 1994, ISBN 3-18-400891-6 , pp. 849-850.
- ^ Association of German Engineers : VDI guideline: Measurement of gaseous immissions; Measuring ammonia concentration; NESSLER procedure , accessed on January 10, 2018