Zinc Carbon

Zinc Carbon Battery

Mass produced F and D cells from around 1896 to 1898 have improved in capacity to current levels by 1939 and by 1950s the shelf life had increased from about 9 months to 3 years. The outer zinc container is the negative terminal. The zinc is oxidised (a white powder) as the battery is used. Thus the outer casing eventually disintegrates. A carbon rod often with a brass cap is surrounded by a powder containing manganese(IV) oxide is the positive terminal. The manganese dioxide is mixed with carbon powder to increase the electrical conductivity
(s) = solid, (aq) = aqueous (gel like usually) Zn(s) + 2MnO2(s) + 2NH4Cl(aq) -> Mn2O3(s) + Zn(NH3)2Cl2 (aq) + H2O
The battery has a voltage (EMF)  of about 1.6V when fresh and no load. This quickly drops to 1.5V then more slowly to 1.1V, the average is about 1.4V. The voltage quickly drops between 1.1V to 0.9V and then it’s exhausted.  The cell could more properly be called a “zinc – manganese” cell. A zinc – carbon dry cell is a primary cell because the cell can’t be recharged. Most original single use cells (up to 1940s) were mostly Zinc Carbon, though Zinc Air and Mercury button cells used in specialist applications before 1940.