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 can be defined as homogeneous if it contains only one kind of compound or one element. Homogeneous is Latin for the same kind. An example of a homogeneous substance would be pure silicon, which contains only silicon atoms. Other examples are pure water, which contains only the compound H2O, or pure table salt, which contains only the compound NaCl.