Fraction

Reagents chemical

Volume (mL)

Time (h)

Exchangeable

1M MgCl₂, pH = 7, 20˚C, continuous agitation

8

1

Acid-soluble ( ${\text{CO}}_3^{2-}$ )

1M CH₃COONa/CH₃COOH, pH5, 20˚C, continuous agitation

8

5

Reducible

(Fe; Mn)

0.04M NH₂OH, HCl + 25%CH₃COOH, 95˚C intermittent agitation

20

6

Oxidizable (M.O.)

30% H₂O₂, 0.02M HNO₃, pH = 2, 85˚C, Intermittent agitation, 3.2M CH₃COONH₄, +20% HNO₃

5

3

5

2

0.5

Residual

40% HF + 60% HClO₄ (Total mineralization)

5

à sec

Total content in Metal

40% HF + 60% HClO₄ (Total mineralization)

10

à sec