Hafnium

Location:  Group 4, Period 6
Atomic Weight:  178.49
Coordination Number:  6, 7, 8
Chemical Form in Solution:  Hf(F)₆^-2
(coordination numbers in green are observed less frequently)

Storage & Handling:  Keep tightly sealed when not in use. Store and use at 20 ± 4°C. Do not pipet from container. Do not return portions removed for pipetting to container.

Chemical Compatibility:  Soluble in concentrated HCl, HF, H₂SO₄ (very hot), and HNO₃. Avoid H₃PO₄and neutral to basic media. Unstable at ppm levels with metals that would pull F^- away (i.e. - do not mix with Alkaline or Rare Earths or high levels of transition elements unless they are fluorinated). Stable with most inorganic anions but precipitation with phosphate, oxalate, and tartrate with a tendency to hydrolyze forming the hydrated oxide in all dilute acids except HF.

Stability:  2-100 ppb levels stable alone or mixed with all other metals that are at comparable levels as the Hf(F)₆^-2 + Hf(OH)₄F₂^-2 for months in 1% HNO₃ / LDPE container. 1-10,000 ppm single element solutions as the Hf(F)₆^-2 chemically stable for years in 2-5% HNO₃ / trace HF in an LDPE container.

Hf Containing Samples (Preparation & Solution):  Metal (soluble in H₂O / HF / HNO₃); Oxide - unlike TiO₂ the HfO₂ is best fused in one of the following ways (Na₂O₂ in Ni⁰, Na₂CO₃ in Pt⁰ or Borax in Pt⁰); Organic Matrices (dry ash at 450°C in Pt⁰ and dissolve by fusing with Na₂CO₃ and dissolving in HF / HNO₃ / H₂O).