Bottle of solution of sodium dodecyl sulfate for use in the laboratory. The critical micelle concentration (CMC) in pure water at 25 Â°C is 8.2 mM, and the aggregation number at this concentration is usually considered to be about 62. The micelle ionization fraction (Î±) is around 0.3 (or 30%).
Definition: A pure substance is a sample of matter with both definite and constant composition with distinct chemical properties.
A substance that has the same composition throughout. Pure substances are either elements or compounds, and should not be confused with mixtures. A homogeneous mixture is not the same as a pure substance, because although it has an unvarying composition, it cannot be reduced to a single type of atom or molecule.