ODM2 Units Type Controlled Vocabulary ODM2 Working Group A vocabulary for describing the type of the Unit or the more general quantity that the Unit represents. Mass fraction In chemistry, the mass fraction is the ratio of one substance with mass to the mass of the total mixture , defined asThe sum of all the mass fractions is equal to 1:Mass fraction can also be expressed, with a denominator of 100, as percentage by weight (wt%). It is one way of expressing the composition of a mixture in a dimensionless size; mole fraction (percentage by moles, mol%) and volume fraction (percentage by volume, vol%) are others. For elemental analysis, mass fraction (or "mass percent composition") can also refer to the ratio of the mass of one element to the total mass of a compound. It can be calculated for any compound using its empirical formula. or its chemical formula Dimensionless Ratio Wikipedia http://dbpedia.org/page/Mass_fraction_(chemistry)