FeClj cathode

This area will be passivated by the increase in pH due to the cathodically produced OH ions, and partially cathodically protected by the electrons liberated by the anodic processes within the pit. The tubercle thus results in an occluded cell with the consequent acidification of the anodic sites. Wranglen considers that in view of the fact that crystals of FeClj -4H20 are sometimes observed at the bottom of a pit the solution within the pit is a saturated solution of that salt, and that this will correspond with an equilibrium pH of about 3-5. 

Colloids of a-FejOj are made by hydrolysis of FeClj and subsequent dialysis of the sol. Polyvinyl alcohol is often used as a stabilizing agent. The band gap in Fe203 is 2.2 eV. In some of the studies on colloidal Fc203 free radicals were generated by ionizing radiation and electron transfer reactions with the colloidal particles investigated. Buxton et al. observed a cathodic dissolution of a-FCjOj in acidic... 

FIGURE 9.21 SECM line profiles above a pore in skin, measured as a function of the tip potential, E. Each of the 16 Ganssian-shaped segments is a plot of (, as a function of the tip position (the Jr-coordinate). Donor solution 0.05M FeCl3+0.05M FeClj. The anodic currents at (>0.5 V vs. Ag/AgCl correspond to detection of Fe as it emerges from the pore. The cathodic currents at Ei<0.5N correspond to detection of Fe. (From Scott, E.R. et al., Solid State Ionics, 53-56, 176, 1992. With permission.)... 

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