Self-diffusion coefficient

{
  "id": "MLC-T-CHM-010707",
  "term": "Self-diffusion coefficient",
  "field": "Chemistry",
  "definition": "A coefficient describing how fast molecules of a substance wander through the pure substance, or through a uniform mixture, by random thermal motion, with no concentration or chemical-potential gradient driving them. It is obtained by following labeled molecules, for example by pulsed-field gradient NMR or tracer experiments, and is stated in m²/s. In water at 25 °C its value is about 2.3 × 10⁻⁹ m²/s.",
  "subject": "Physical and Biophysical Chemistry",
  "see_also": [
    "chemical potential",
    "diffusion",
    "diffusion coefficient",
    "gradient",
    "isotope effect",
    "isotopically labelled",
    "tracer"
  ],
  "references": [
    "PAC, 1972, 31, 577. 'Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry' on page 617 (https://doi.org/10.1351/pac197231040577)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/self-diffusion-coefficient/"
}