1. 1 distance Potential - - - - + + + + + + - - + - - + - + + - - - - Diffuse Layer Bulk Solution + dd IHPOHP The electrical double layer + + + - ii

2. 2  : zeta potential  : liquid conductivity  : viscosity  : liquid permittivity  P: pressure difference from inlet to outlet  s : measured streaming potential

3. 3  : zeta potential  : liquid conductivity : kinematic viscosity  : liquid permittivity a: disk radius z: distance of reference electrode from sample  : rotation rate  s : measured streaming potential

4. 4 distance Plane of shear (possibly) Potential  - - - - + + + + + + - - + - - - + - + + + - - - - Diffuse Layer Bulk Solution + dd IHPOHP + + The plane of shear

5. 5 voltmeter Sample solid Liquid Reference electrode (e.g. Ag/AgCl) piston/pump A schematic of the parallel plate capillary system. receptacle

6. 6 voltmeter Liquid Reference electrode Sample solid Schematic of the rotating disk system

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8. 8  zeta potential R: gas law constant T: temperature z: 1, for a 1:1 salt F: faraday’s constant : Debye length q 2 :charge density of the diffuse layer  : permittivity of water

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