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| Separators. Separators are made of molded hard rubber and support each edge of each individual plate after the two groups of plates have been intermeshed. They thus provide not only the necessary insulation of the plates from one another and the container, but also the physical support for the weight of the plates on the container bottom. Additional insulation between the flat faces of each positive and negative plate is provided by molded hard-rubber pins or spacers. |

| Electrolyte. The electrolyte is a 21-percent solution of potassium and lithium hydroxides having a normal specific gravity of approximately 1.2 at 16°C or 60°F. Sodium hydroxide is sometimes used instead of potassium hydroxide. The concentration and chemical composition of this electrolyte do not change materially during the periods of charge and discharge. |

| Container. The container is made of nickel-plated sheet steel with all sides welded together. The cover is fitted with gas- and liquid-tight insulated openings for the terminals. Gas valves in the cell-vent plugs protect the electrolyte from contamination by carbon dioxide from the air. (Carbon dioxide forms carbonates in the electrolyte that increase its resistivity.) The valves allow the escape of generated gases while preventing the entrance of air. Often, when alkaline batteries are being charged, a popping sound is heard as gas displaces the spring-loaded valve. |

| A cross section of the alkaline cell and its container is shown in Fig. 15-8. Cells are connected together by means of nickel-plated copper straps and must be insulated from one another because the steel containers are electrical conductors. |

| Figure 15-8 Alkaline cell construction (Courtesy, Exide Battery Co.) |

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