Green coke is calcined prior to being used for the fabrication of anodes for the electrolytic production of aluminium. A criterion for the degree of calcination is the hydrogen residue. This International Standard specifies a method for determining the residual-hydrogen content of calcined coke used in the production of aluminium. The method is only applicable to products having a residual-hydrogen content of less than 1 % (mlm). NOTE - At concentrations of less than 1 % (m/m), hydrogen is mainly bound to condensed aromatic rings and less to side chains.