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.
Supplement. In biology, the term substance is used to refer to the material constituting an organ, e.g. ground substance or spongy substance. In chemistry, all compounds are substances but not all substances are compounds since pure elements are also chemical substances.oun, plural:substances. (1) The physical matter, material or that of which an organ or body consists. (2) (chemistry) A material, matter or that which has definite chemical composition and distinct properties. (3) The most vital or essential part of something. (4) Drugs, as in substance abuse.