REAGENTS
3.—3.1 Hydrochloric acid (density at 20°C ρ = 1.18 g/ml).
3.2 Hydrochloric acid, 6 M solution.
3.3 Hydrochloric acid, 0.5 M solution.
3.4 Ammonium nitrate.
3.5 Hydrogen peroxide, 30%.
3.6 Copper solution(1) (stock): weigh, to the nearest 0.001 gram, 1 gram of pure copper, dissolve in 25 ml of 6 M hydrochloric acid solution (3.2), add 5 ml of hydrogen peroxide (3.5) in portions and dilute to 1 litre with water. 1 ml of this solution contains 1,000 μg of copper (Cu).
3.6.1Copper solution (dilute): dilute 10 ml of stock solution (3.6) to 100 ml with water and then dilute 10 ml of the resulting solution to 100 ml with water. 1 ml of the final dilution contains 10 μg of copper (Cu).
Prepare this solution at the time of use.
Commercially available standard copper solution may be used.