Norsk Hydro process
The Norsk Hydro process starts with a magnesium brine which could be prepared from a mineral base, sea water or bittern dependent on comparative costs. The brine is then purified, concentrated and dehydrated in prilling towers to pure anhydrous magnesium chloride. The by-product chlorine from the electrolysis may be sold or recycled to the process.  This process has been applied since 1970.