Composition and preparation of Nessler’s reagent for detection of ammonia and ammonia salts

Composition and preparation of Nessler’s reagent for detection of ammonia and ammonia salts

Nessler’s reagent is a alkalic solution of potassium iodide, mercuric chloride, and potassium hydroxide. Nessler’s reagent detects production of ammonia and ammonia salts. The solution turns yellow if ammonia is present, and it may precipitate at higher concentration.

Constituent                Amount
Potassium iodide50.0 g
Distilled water (ammonia free)25.0 ml
Mercuric chloride (saturated)35.0 ml
Potassium hydroxide (50% aqueous) 400.0 ml

Procedure:

  • Dissolve Potassium iodide in 35 ml of Distilled water and add saturated solution of mercuric solution until a slight precipitate persists.
  • Then add Potassium hydroxide.
  • Dilute the solution to 1000 ml by addition of distilled water.
  • Allow to settle for one week, decant supernatant liquid, and store in tightly stoppered brown bottles.

Principle and Interpretation:

Bacteria growing in natural environment decompose urea by the means of an enzyme urease. Ammonia produced from urea decomposition is measured with either pH indicator or Nessler’s reagent.

  1. By growing the organism in the presence of urea and measuring for alkali (NH3) production. Suitable pH indicator detects the ammonia production.
  2. test for the production of ammonia from urea by means of Nessler’s reagent and/or to detect NH3 production due to L-arginine breakdown

 

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