Stoffractie

Stoffractie is a term used in Dutch-language scientific literature to denote the proportion of a mixture that is made up by a particular substance. In many contexts, it corresponds to the mass fraction, also called the massa-fractie, of a component in a mixture. It can also refer more generally to any fraction of interest, such as a volume fraction or a mole fraction, depending on the measurement basis.

For a mixture with components i, j, the mass fraction w_i is defined as w_i = m_i / (Σ_k m_k). When expressed as a percentage, w_i × 100% is the mass percent. If the basis is volume, the corresponding volume fraction is V_i / V_total; for moles, the mole fraction x_i = n_i / n_total.

Stoffractie is widely used in material science, chemistry, environmental science, and related fields to quantify composition, inform quality control, formulation, and processing decisions.

Example: a sample contains 20 g of substance A and 80 g of substance B, then the mass fraction of A is 0.20 (20%), and B is 0.80 (80%).

Important notes: fractions depend on the chosen basis; mass fraction is not the same as mole fraction, especially for substances with different molar masses; non-ideal mixtures may require alternative reporting bases for consistency.

Etymology: the word stems from the Dutch "stof" meaning substance and "fractie" meaning fraction.

See also: mass fraction, mole fraction, volume fraction, composition analysis.