Methods Manual
 
Controlled Document - MTH 92
- Ver 2
- 17/9/82
SOP: Determination of Ammonia by Titration with Sulfuric Acid

Background
Ammonia is found as ammonium hydroxide in solution and reacts with sulfuric acid according to the following equation.

Sulfuric acid + ammonium hydroxide water + ammonium sulphate

H2SO4 + 2NH4OH 2H2O+ (NH4)2SO4

Use previously standardised 0.05M sulfuric acid.

All volumetric glassware used in this procedure is Class A.
Standard PPE should be worn when performing this work.

Method
  1. Using a bulb pipette, quantitatively transfer a 10 mL aliquot of the cleaning solution sample to a 100 mL volumetric flask. Dilute to the mark with distilled water, replace the stopper and mix the contents by inverting and swirling the flask a number of times.

  2. Using a bulb pipette, quantitatively transfer a 25 mL aliquot of the diluted cleaning solution sample to a 250 mL Erlenmeyer flask. Wash down the inside of the flask with about 50 mL of distilled water delivered from a wash bottle.

  3. Add 2 drops of methyl red indicator and mix well.

  4. Carefully fill a 50 mL burette with standard 0.05 M sulfuric acid solution, M (sulfuric). Note that this solution must be freshly standardised before use.

  5. Titrate the diluted cleaning solution to the first sign of a permanent pink end point (use a white tile beneath the Erlenmeyer flask during the titration). Record the titre to the nearest 0.01 mL.

  6. Repeat the titration (steps 2 to 5) until three titres are obtained that agree within 0.10 mL. Average these readings T (sulfuric).

  7. Calculate the concentration of ammonia hydroxide available in the undiluted cleaner sample C (ammonia), % w/v to 2 decimal places:

C (ammonia) =  2 x M (sulfuric) x T (sulfuric) x Mr (ammonia)

25

Where Mr (ammonia) is the formula mass of ammonium hydroxide


Senior Technician's office >> Methods Manual >>SOP: Determination of Ammonia by Titration with Sulfuric Acid Close