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Specifies methods for the calculation of the superior calorifi c value, inferior calorific value, density, relative density a nd Wobbe index of dry natural gases, natural gas substitutes a nd other combustible gaseous fuels, when the composition of th e gas by mole fraction is known. The methods prodive a means o f calculating the properties of the gas mixture at commonly us ed metric reference conditions. The methods of calculation req uire values for various physical properties of the pure components; these values are provided in tables and their sources ar e identified. Methods are given for estimating the precision o f calculated properties. The methods of calculation of the val ues of properties on either a molar or mass basis are applicab le to any dry natural gas, natural gas substitute or other com bustible fuel which is normally gaseous. For the calculation o f the values of properties on a volumetric basis, the methods are restricted to gases consisting preponderantly of methane ( not less than 0,5 mole fraction).