Dissolve the ingredients of each solution in the appropriate quantities of
water. Bring solution A to the boil for a few minutes, then cool to room
temperature while gassing with oxygen-free N2 gas. Add solution
B and C, adjust pH to 7.8 with NaOH, and distribute under N2 in
anaerobic tubes. During distribution continuously swirl the medium to keep
the grey precipitate suspended. Autoclave 15 min at 121°C.