This International Standard specifies a gravimetric method for the determination of the mass fraction of insoluble (free) carbon in carbides and hardmetals. This method is applicable to - carbides of hafnium, molybdenum, niobium, tantalum, titanium, vanadium, tungsten and zirconium, - mixtures of these carbides and binder metals, free of lubricant, and - all grades of presintered or sintered hardmetals, produced from these carbides, having a mass fraction of insoluble carbon between 0,02 % and 0,5 %.