Dissolution of the positive electrode as the principal oxidation reaction involved in the generation of hydroxide (HO-) in button battery injury.

PURPOSE: Button battery injury results from tissue alkalization due to the generation of HO- at the negative electrode by electrolysis. Here, we conducted in vitro experiments to test the hypothesis that the principal oxidation reaction occurs at the positive electrode and is the result of dissolution of metals constituting the electrode, and in the case of 3 V batteries, H2O and chloride ions (Cl-) are also oxidized.

METHODS

1) Physiological saline solutions were electrolyzed at 1.5 or 3 V in agarose gel for 2 h with an iron (Fe) nail or non-dissolving carbon (C) rod as the positive electrode. HO- generation was visualized using a pH indicator. 2) A 1.5 or 3 V button battery was placed in agarose gel for 2 h.

RESULTS

1) At 1.5 V, HO- was generated with a positive Fe electrode but not with a positive C electrode. At 3 V, HO- was generated with a positive C electrode, although less intensely. At both voltages, precipitates formed where the diffusion fronts of HO- and dissolved Fe2+ met. 2) Precipitate was formed on the rim of the button battery where the ionic current was the most intense and dissolution proceeded.

CONCLUSION

At 1.5 V, dissolution of the positive electrode was nearly the sole oxidation reaction. At 3 V, H2O and Cl- were also oxidized. These results confirm the hypothesis. Clinically, visible dissolution (corrosion) of the rim of the button battery on plain radiography could indicate considerable HO- concentration, suggesting higher-grade mucosal injuries and more severe complications.