Regulation (EC) No 648/2004 of the European Parliament and of the CouncilShow full title

3.2. Reagents and Equipment U.K.

Reagents are to be made up in deionised water.

3.2.1. Pure ethyl acetate, freshly distilled. U.K.

3.2.2. Sodium bicarbonate, NaHCO₃ AR. U.K.

3.2.3. Dilute hydrochloric acid [20 ml concentrated acid (HCl) diluted to 1 000 ml with water] U.K.

3.2.4. Methanol AR, freshly distilled, stored in a glass bottle. U.K.

3.2.5. Bromocresol purple, 0,1 g in 100 ml methanol. U.K.

3.2.6. Precipitating agent: the precipitating agent is a mixture of two volumes of solution A and one volume of solution B. The mixture is stored in a brown bottle and can be used for up to one week after mixing. U.K.

3.2.6.1. Solution A U.K.

Dissolve 1,7 g bismuth nitrate, BiONO₃.H₂O AR, in 20 ml glacial acetic acid, and make up to 100 ml with water. Then dissolve 65 g potassium iodide AR in 200 ml water. Mix these two solutions in a 1 000 ml measuring flask, add 200 ml glacial acetic acid (3.2.7) and make up to 1 000 ml with water.

3.2.6.2. Solution B U.K.

Dissolve 290 g barium chloride, BaCl₂.2H₂O AR, in 1 000 ml of water.

3.2.7. Glacial acetic acid 99-100 % (lower concentrations are unsuitable). U.K.

3.2.8. Ammonium tartrate solution: mix 12,4 g tartaric acid AR and 12,4 ml of ammonia solution AR (d = 0,910 g/ml) and make up to 1 000 ml with water (or use the equivalent amount of ammonium tartrate AR). U.K.

3.2.9. Dilute ammonia solution: 40 ml ammonia solution AR (d = 0,910 g/ml) diluted to 1 000 ml with water. U.K.

3.2.10. Standard acetate buffer: dissolve 40 g solid sodium hydroxide AR, in 500 ml water in a beaker and allow to cool. Add 120 ml glacial acetic acid (3.2.7). Mix thoroughly, cool and transfer to a 1 000 ml volumetric flask. Make up to the mark with water. U.K.

3.2.11. Pyrrolidinedithiocarbamate solution (known as ‘carbate solution’): dissolve 103 mg sodium pyrrolidinedithiocarbamate, C₅H₈NNaS₂.2H₂O, in about 500 ml water, add 10 ml of n-amyl alcohol AR and 0,5 g NaHCO₃ AR, and make up to 1 000 ml with water. U.K.

3.2.12. Copper sulphate solution (for standardisation of 3.2.11). U.K.

STOCK SOLUTION U.K.

Mix 1,249 g copper sulphate, CuSO₄.5H₂O AR, with 50 ml 0,5 M sulphuric acid and make up to 1 000 ml with water.

STANDARDSOLUTION U.K.

Mix 50 ml stock solution with 10 ml 0,5 M H₂SO₄ and make up to 1 000 ml with water.

3.2.13. Sodium chloride AR. U.K.

3.2.14. Gas-stripping apparatus (see Figure 5). U.K.

The diameter of the sintered disc must be the same as the internal diameter of the cylinder.

3.2.15. Separating funnel, 250 ml. U.K.

3.2.16. Magnetic stirrer with magnet 25-30 mm. U.K.

3.2.17. Gooch crucible, diameter of the perforated base = 25 mm, Type G4. U.K.

3.2.18. Circular glass-fibre filter papers, 27 mm diameter with fibre diameter 0,3-1,5 m. U.K.

3.2.19. Two filter flasks with adapters and rubber collars, 500 and 250 ml respectively. U.K.

3.2.20. Recording potentiometer fitted with a bright platinum indicator electrode and a calomel or silver/silver chloride reference electrode with a 250 mV range, with automatic burette of 20-25 ml capacity, or alternative manual equipment. U.K.