Paragraph 4 REAGENTS

Diluted hydrochloric acid solution (HCl), about 6 M

4.1

Mix one volume of hydrochloric acid (ρ = 1.18 g/ml) with 1 volume of water.

Diluted hydrochloric acid solution (HCl), about 0.5 M

4.2

Mix one volume of hydrochloric acid (ρ = 1.18 g/ml) with 20 volumes of water.

Lanthanum salt solutions (10 g of La per litre).

4.3

This reagent is used for determinations of iron and zinc. Lanthanum is added to the extract to eliminate chemical interferences in the air-acetylene flame. It can be prepared either:

(a)

with lanthanum oxide dissolved in hydrochloric acid (4.1). Place 11.73 g of lanthanum oxide (La₂O₃) in 150 ml of water in a 1 litre volumetric flask and add 120 ml of 6 M hydrochloric acid (4.1). Allow to dissolve and then make up to 1 litre with water and mix thoroughly. This solution is approximately 0.5 M in hydrochloric acid; or

(b)

with solutions of lanthanum chloride, sulfate or nitrate.

Place 26.7 g of lanthanum chloride heptahydrate (LaCl₃7H₂O) or 31.2 g of lanthanum nitrate hexahydrate (La(NO₃)₃6H₂O) or 26.2 g of lanthanum sulfate nonahydrate (La₂(SO₄)₃9H₂O) in 150 ml of water in a 1 litre volumetric flask, then add 85 ml of 6 M hydrochloric acid (4.1). Allow to dissolve and then make up to 1 litre with water. Mix thoroughly. This solution is approximately 0.5 M in hydrochloric acid.

Calibration solutions

4.4

For the preparation of these, see the individual methods of determination for each trace element.