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.
: Chemical substances are any materials (in any state-solid, liquid or gas) that have a definite chemical composition. Chemical substances can therefore be. a pure chemical element. a pure chemical compound.This definition and interpretation is generally considered sufficient for school-level, incl GCSE Chemistry.There are, however, some other definitions e.g.  A form of matter that has both definite composition and distinct properties. Chemical substances are any materials (in any state-solid, liquid or gas) that have a definite chemical composition. Chemical substances can therefore be. a pure chemical element. a pure chemical compound.