
209Metal Refining and Purification
MgCl
2
+ 2Na = Mg + 2NaCl (slag) (12.19)
MgCl
2
+ Ca = Mg + CaCl
2
(slag) (12.20)
These uxes are premelted with KCl (to prevent hydration of the MgCl
2
) at one of
several compositions corresponding to eutectics in the KCl–MgCl
2
system. The price
of KCl is volatile, so Courtenay (2011) has demonstrated that satisfactory sodium
removal can be achieved with an MgCl
2
–KCl–NaCl eutectic ux that reduces the
cost. Adding 1–3 wt.-% uorspar (CaF
2
) improves reaction efciency.
Many of the same methods for improving degassing kinetics also improve
the kinetics of reactive-metal removal. The effectiveness of chlorine injection ...