HCl has a higher conductivity that the indicator solution , and therefore a lower electric field to carry the same current. If a more mobile ion diffuses into the solution, it will rapidly be accelerated back to the boundary by the higher electric field; if a less mobile ion diffuses into the HCl solution it will decelerate in the lower electric field and return to the solution. Also the apparatus is constructed with the anode below the cathode, so that the denser solution forms at the bottom. The cation transport number of the leading solution is then calculated as where is the cation charge, the concentration, the distance moved by the boundary in time , the cross-sectional area, the Faraday constant, and the electric current. Concentration cells This quantity can be calculated from the slope of the function of two concentration cells, without or with ionic transport. The EMF of transport concentration cell involves both the transport number of the cation and its activity coefficient: where and are activities of HCl solutions of right and left hand electrodes, respectively, and is the transport number of . Electrophoretic magnetic resonance imaging method This method is based on magnetic resonance imaging of the distribution of ions comprising NMR-active nuclei (usually 1H, 19F, 7Li) in an electrochemical cells upon application of electric current See also Activity coefficient Born equation Debye length Electrochemical kinetics Einstein relation (kinetic theory) Ion selective electrode ITIES Liquid junction potential Law of dilution Solvation shell Solvated electron Thermogalvanic cell van't Hoff factor Notes External links Aqueous Symple Electrolytes Solutions, H. L. Friedman, Felix Franks Electrochemistry Physical quantities