Paragraph 4 REAGENTS

Dilute hydrochloric acid (HCl) solution, about 6 M:

4.1

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

Dilute hydrochloric acid (HCl) solution, about 0.5 M:

4.2

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

4.3

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

This reagent is used for determinations of cobalt, iron, manganese 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 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 (LaCl₃.7H₂O) or 31.2 g of lanthanum nitrate hexahydrate [La(NO₃)₃.6H₂O] or 26.2 g of lanthanum sulfate nonahydrate [La₂(SO₄)₃.9H₂O] 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 method of determination for each trace element.