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| The chemical reactions are represented by the same equations given above for discharge, except that they are now read from right to left to reverse their direction. It was noted that some of the hydrogen and oxygen occasionally escapes before being reformed into water. Water may thus have to be added from time to time to make up for this deficiency. It should also be noted that the equations represent the normal chemical reactions that take place. If impurities are present, other reactions may occur. |

| Alkaline Storage Battery.. |

| The chemical reactions that take place in the nickel-iron-alkaline cell are different from those occurring in the lead-acid cell. When fully charged, the active materials of the alkaline storage battery consist of nickel dioxide (NiO2) in the positive plate and metallic iron (Fe) in the negative plate. The electrolyte is a solution of potassium hydroxide (KOH) in water (H2O), to which lithium hydroxide is added as a catalyst. |

| Discharge. |

| During discharge (Fig. 15-4A), the active material in the positive plate, nickel dioxide, is reduced to nickel oxide (NiO) and that in the negative plate, iron, is oxidized to form iron oxide (FeO). Although the electrolyte, potassium hydroxide, appears to undergo no change, it does take an active part, breaking up into its component ions of potassium and hydroxide and then reforming into potassium hydroxide. The chemical reactions that take place may be represented by simple chemical equations: |

| Fe + 2KOH + H2O + NiO2 |

| ionizes into |

| Fe + 2K + 2O + 2H + 2H + O + Ni + 2O |

| One O of 2KOH joins Fe to form FeO (iron oxide), and one O of NiO2 is released to form NiO (nickel oxide). When the 2K + O + 2H forms H2O, it releases the 2K, which then joins with the original H2O and the O released from the nickel oxide to form 2KOH. The overall equation is as follows: |

| Fe + 2KOH + H2O + NiO2 = FeO + 2KOH + H2O + NiO |

| Charge |

| During the charging cycle (Fig. 15-4B), the reverse action takes place, with the same breakdown of the potassium peroxide and water into ions and |

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