text: Zinc–carbon batteries were the first commercially available battery type and are still somewhat frequently used, although they have largely been replaced by the similarly composed alkaline battery. Like the alkaline battery, the zinc–carbon battery contains manganese dioxide and zinc electrodes. Unlike the alkaline battery, the zinc–carbon battery uses ammonium chloride as the electrolyte (zinc chloride in the case of "heavy-duty" zinc–carbon batteries), which is acidic.
  Either when it has been completely consumed or after three to five years from its manufacture (its shelf life), a zinc–carbon battery is prone to leaking. The byproducts of the leakage may include manganese hydroxide, zinc ammonium chloride, ammonia, zinc chloride, zinc oxide, water and starch. This combination of materials is corrosive to metals, such as those of the battery contacts and surrounding circuitry.
  Anecdotal evidence suggests that zinc–carbon battery leakage can be effectively cleaned with sodium bicarbonate (baking soda).