Paragraph 4 REAGENTS
Hydrochloric acid solution, about 6M
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).
Cobalt calibration solutions
4.4
Cobalt stock solution (1000 μg/ml)
4.4.1
In a 250 ml beaker, weigh to the nearest 0.1 mg, 1 g of cobalt, add 25 ml of 6 M hydrochloric acid (4.1) and heat on a hot plate until the cobalt is completely dissolved. When cool, transfer quantitatively to a 1000 ml volumetric flask. Make up to volume with water and mix thoroughly.
Cobalt working solution (100 μg/ml)
4.4.2
Place 10 ml of the stock solution (4.4.1) in a 100 ml volumetric flask. Make up to volume with 0.5 M hydrochloric acid solution (4.2) and mix thoroughly.