Birnessite, Na,K Mn IV Mn III O 4 xH 2 O, is a mineral with a layered structure of the same type as CdI 2 (see Fig 6 25) comprising octahedral MnO6 units Na and K ions and H 2 O molecules are sited between the layers The Na K composition is variable Analysis for Na is carried out using AAS A 20 mg ...

a Birnessite is treated with acid to dissolve the mineral and release the Na and K ions The acid als ...

Birnessite, [Na,K][Mn IV Mn III ]O 4 xH 2 O, is a mineral with a layered

Question:

Birnessite, [Na,K][Mn^IVMn^III]O₄ · xH₂O, is a mineral with a layered structure of the same type as CdI₂ (see Fig. 6.25) comprising octahedral MnO6 units. Na⁺ and K⁺ions and H₂O molecules are sited between the layers. The Na/K composition is variable. Analysis for Na is carried out using AAS. A 20 mg sample of birnessite is dissolved in concentrated HCl/HNO₃ and the solution made up to 200 cm³ in a volumetric flask.

(a) Why is birnessite treated with acid?

(b) Detail how you would proceed with the sodium analysis.

Figure 6.25