D vs 1/a Graph

Fig. 1. Diffusion of weak electrolytes of known diffusion coeficient, D (cm2/sec), and Stokes radius, a (Angstroms).   A. Confirmation of water (H2O) behaving as a weak electrolyte and the hydronium ion (H3O+) behaving anomalously with a high apparent D The regression of electrolytes with known D and a (filled diamonds) includes alpha-alanine, beta-alanine, citric acid, glycine, glycyl-glicine, HEPES, meta-, ortho-, and para- amino-benzoic acids, and urea.   B. Estimation of D (open squares) for several Good buffers based on their weak electrolyte properties and an estimate of their Stokes radius from molecular models. The linear regression of weak electrolyte D vs 1/a derived from panel A is plotted and used to estimate the expected D for the buffers MESS, Tricine, ACES and MOPS.

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