Oceanography

3. Reagents

1. Ammonia –free water

Deionised water is usually recommended for the preparation of reagents for NH₃ estimation. The NH₃ free water may also be prepared by boiling distilled water containing 2-3 drops of bromine liquid. Ordinary distilled water can also be distilled again with 2 ml of conc. H₂SO₄ and 1 g of K₂S₂O₈ (Potassium persulphate) to get ammonia free water.

2. Phenol-nitroprusside solution

27 g phenol and 0.30g of sodium nitroprusside dehydrate are dissolved in NH₃ free distilled water and the solution is made up to 1 litre. This reagent is stable for many months if stored in a refrigerator in a dark glass bottle.

3. NaOH solution (0.84M)

33.6 g of NaOH is dissolved in NH₃ free water and is made up to 1 litre.

4. Sodium hypochlorite solution

Commercial grade NaOCL or bleaching powder (6.25% solution) is used.

4. Trisodium citrate solution (1.19 M)

350 g of C6H5Na3O2. 2H2O is dissolved in distilled water and is made up to 1 litre.