Abstract For calculating the true relative density the mass of water displaced by a known masss of dry coke, ground to pass a sieve of nominal size of openings 212 um, is determined using a pyknometer. - The volume of a large amount of coke is determined by displacement in water; dividing the mass of the dried coke by the mass of an equal volume of water gives the apparent relative density. - The porosity is calculated from the true relative density and the apparent relative density of the coke.