Which of the following does not represent a correct method for the extraction or refining of metals?

• A
  $TiCl_4 + 2Mg \to Ti + 2MgCl_2 : \text{Kroll process}$
• B
  $Ni(CO)_4 \to Ni + 4CO : \text{Mond process}$
• C
  $Ag_2CO_3 \to 2Ag + CO_2 + \frac{1}{2}O_2 : \text{Van Arkel process}$
• D
  $ZrI_4 \to Zr + 2I_2 : \text{Van Arkel process}$