Chloride content in Thermal insulation Material
The chloride present in the sample is extracted by titration method with silver nitrate.
- Burette – 50 ml
- Conical flask – 250
- Whatman Filter Paper No. 42
- Beaker – 500 ml
- Water bath
- Silver nitrate (0.0141 N) – Dissolving 2.396 g of silver nitrate in distilled water and dilute to 1 liter.
- Potassium Chromate – Dissolving 50 g of potassium chromate in distilled water. Add silver nitrate solution till a definite red precipitate is formed. Allow to stand overnight and filter. Dilute the filtrate to 1 liter with distilled water.
- Sodium Chloride (0.0141 N) – Dissolving 0.8241 g of NaCl in distilled water and dilute to 1 liter.
- 0.1 N Sulphuric Acid
- 0.1 N Sodium Hydroxide
- Distilled water.
- Take 30 g of mineral fibre in a 500 ml beaker and 300 ml chloride-free distilled water.
- Cover the beaker and place it in a steam bath overnight and add fresh water for evaporation losses.
- Filter through Whatman No. 42 or equivalent filter paper.
- Take 100 ml of the above extract and adjust the pH in the range 7 to 10 by adding 0.1 N sulphuric acid or 0.1 N sodium hydroxide solution.
- Add 1 ml of potassium chromate indicator solution.
- Titrate with standard silver nitrate solution to a pink-yellow end point. Run a blank also.
NOTE — Chloride contamination should be avoided at all stages during test.
Chlorides (as Cl), % = (V1-V2) × 0.05 / M
V1 = volume, in ml, of standard silver nitrate solution used in the titration with test sample;
V2 = Volume in ml of standard silver nitrate solution used in the blank;
Reference Standard: IS 3144 (Cl. 26) :1992