Paragraph 4 REAGENTS

Hydrochloric acid solution, about 6 M

4.1

See Method 25d (4.1).

Hydrochloric acid solution, about 0.5 M

4.2

See Method 25d (4.2).

Lanthanum salt solutions (10 g of La per litre)

4.3

See Method 25d (4.3).

Zinc calibration solutions

4.4

Zinc stock solution (1000 mg/ml)

4.4.1

In a 1 litre volumetric flask dissolve 1 g of zinc powder or flakes weighed to within 0.1 mg in 25 ml of 6 M hydrochloric acid (4.1). When completely dissolved, make up to volume with water and mix thoroughly.

Zinc working solution (100 mg/ml)

4.4.2

Place 20 ml of the stock solution (4.4.1) in a 200 ml volumetric flask. Make up to volume with 0.5 M hydrochloric acid solution (4.2) and mix thoroughly.