Chemistry of water -Part 24-

Nitrite titration:

• 2- The sulfanilamide method:
  This process is based on the diazotization of sulfanilamide with nitrite that has been dissolved in water, then the resulting compound is joined to "C10H7NHCH2NH2, 2HCl" to give a coloured complex that can be measured by a spectrophotometer at a wavelength of 537 nm.

3D model of a sulfanilamide molecule

Diazotization reagent:
To 800 ml of distilled water, 100 ml of concentrated phosphoric acid, 40 g of sulfanilamide (C6H8N2O2S) and 2 g of "C10H7NHCH2NH2, 2HCl" are added. The mixture is stirred well until complete dissolution occurs, then we complete with distilled water, the volume to a liter. The reagent is stored and can be used for several months.

In 50 ml of the water to be analysed, 1 ml of diazotization reagent is added, the solution is mixed well, then left for ten minutes, after that the absorbance is measured at the wavelength of 537 nm. The result is compared with the standard curve of solutions of known concentration and performed under the same previous conditions.

References:

• [AQUAPROX- Livre: Traitement des eaux de refroidissement. Imprimé en France par EMD S.A.S- 53110 Lassay-les-Chateaux. N° d'imprimeur: 15566- Dépot légal: juin 2006. N° 842- Cyclus print 90°]

• [Introduction to Water Chemistry (Pollution- Treatment- Analysis). Dr. Nasser Al-Hayek. Publication of the Higher Institute for Applied Sciences and Technology (HIAST). Syrian Arab Republic, 2017.]

• "Chapter A2. Selection of Equipment for Water Sampling" (PDF). National Field Manual for the Collection of Water-Quality Data (Report). Techniques of Water-Resources Investigations, Book 9. Reston, VA: U.S. Geological Survey. March 2003.

• Folco Laverdière, Anja Holstein, Laurent Thiebaut, Robert Mallee, Guillaume Gravejat, Benjamin Des clozeaux: Les principales methodes d’analyse,1999, p5.