Diffusion coefficient of water in water

Value 2300 µm^2/sec
Organism Generic
Reference Noam Agmon, The Grotthuss mechanism, Chemical Physics Letters 244 (1995) 456-462, doi:10.1016/0009-2614(95)00905-J p.458 left column top paragraph
Primary Source R.A. Robinson and R.H. Stokes, Electrolyte solutions, 2nd Ed. (Butterworths, London, 1959) T. Erdey-Gruz, Transport phenomena in aqueous solutions (Adam Hilger, London, 1974).
Method The water self diffusing coefficient is derived by subtracting the abnormal proton diffusion coefficient 7,000µm^2/sec (BNID 106702) from the proton diffusion coefficient 9,300µm^2/sec
Comments "The NMR proton hopping times, tp, account for the abnormal proton mobility if one assumes that hopping is across a single water molecule at a time. Using the Einstein relation for mobility in three dimensions D = I^2/6tp, Meiboom was able to estimate a reasonable proton diffusion coefficient [ref 26]. Let us slightly modify this estimate by taking the hopping length as l = 2.5 Å, the hydrogen-bond length between water and H30+ [ref 8], rather than the water-water distance of 2.8 Å. Using tp = 1.5 ps gives D = 7 × 10^-5 Cm^2/s, a very reasonable estimate for the abnormal proton mobility at room temperature (subtract from the proton diffusion coefficient, 9.3 x 10^-5 cm^2/s, the water self-diffusion coefficient, 2.3 x 10^-5 cm2/s [ref 1]). Even the most modest coherent effect, with proton hopping across just two water molecules, already leads to a factor of 4 in the predicted mobility. Thus proton mobility is best described as an incoherent, Markovian hopping process." See BNID 104087
Entered by Uri M
ID 106703