Assay of Ammonium Chloride by Acid-Base Titration
Aim: To perform the assay of ammonium chloride by acid-base titration.
Requirements:
- Apparatus: Beaker, Funnel, Pipette, Burrette.
- Chemicals: Ammonium chloride, Potassium hydrogen phthalate, Phenolphthalein, Sodium hydroxide solution.
Monograph: Ammonium chloride.
NH4Cl Molecular weight 53.5.
Ammonium chloride contains not less than 99.0 per cent and not more than 100.5 per cent of Cl, calculated on a dried basis.
- Category: Expectorant; diuretic; systemic acidifier.
- Dose: 3 to 6 g daily, in divided doses.
- Description: Colourless crystals or a white crystalline powder.
Procedure:
(A) Standardisation of NaOH: Weigh accurately about 5 g of potassium hydrogen phthalate previously powdered and dried at 120°C for 2 hours, and dissolve in 75 ml carbon dioxide-free water. Add 0.1 ml phenolphthalein solution and titrate with the sodium hydroxide solution until a permanent pink colour is produced. 1 ml of 1 M sodium hydroxide is equivalent to 0.2042 g of potassium hydrogen phthalate.
(B) Assay: Weigh accurately about 0.1 g, dissolve in 20 ml of water and add a mixture of 5 ml of formaldehyde solution, previously neutralised to dilute phenolphthalein solution, and 20 ml of water. After 2 minutes, titrate slowly with 0.1 M sodium hydroxide using a further 0.2 ml of dilute phenolphthalein solution as an indicator.
1 ml of 0.1 M sodium hydroxide is equivalent to 0.005349 g of NH4Cl.
Observation Table: (Standardization)
| Sr. No. | Parameters | Reading |
| 1. | Burette solution | NaOH solution |
| 2. | Conical flask solution | Potassium hydrogen phthalate, water |
| 3. | Indicator | Phenolphthalein |
| 4. | Endpoint | Colourless to pink |
| Burette reading (B.R) (ml) | Trial 1 | Trial 2 | Trial 3 | Average (BR) |
Observation table: (Assay)
| Sr. No. | Parameters | Reading |
| 1. | Burette solution | NaOH solution |
| 2. | Conical flask solution | Ammonium chloride, Formaldehyde |
| 3. | Indicator | Phenolphthalein |
| 4. | Endpoint | Colourless to pink |
| Burette reading (B.R) (ml) | Trial 1 | Trial 2 | Trial 3 | Average (BR) |
Factor: 1 ml of 0.1 M sodium hydroxide is equivalent to 0.005349 g of NH4Cl.
Result: The % purity of ammonium chloride is …….
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