Page 12 - Curriculum Visions Dynamic Book

Zinc cells
On pages 10 and 11 we saw how zinc reacted with a copper salt solution. The flow of ions involved in the exchange of metals is actually a flow of electricity, but this is not noticeable because the ions have not been channelled into an orderly flow (such as happens, for example, with the flow of electrons in a wire). The first person to make a cell that produced electricity was Alessandro Volta in 1796. He saw that
if the zinc could be kept separate from
the copper, then he could make ions flow in an orderly way within the cell. In this way, he could create an electric current (of electrons) in a wire outside the solutions. Using these principles, he created a chemical battery using an electrolyte of animal hide soaked in vinegar.
The difficulty with the Volta cell was that one of the electrodes suffered badly from corrosion. To overcome this problem (and to make it possible to use a battery to supply a steady flow of electricity for the newly invented telegraph), in 1836 the British chemist John Daniell made a chemical battery with zinc, in a porous pot of zinc sulphate and copper, in a flask of copper sulphate. When a wire was connected between them, ions could flow through the porous pot, thus producing
a flow of electricity.
Further development of the Daniell cell led to the Leclanché cell, or common dry battery (shown on page 14).
 A Daniell cell. Notice that the current in the electrolyte is carried by ions, whereas the current in the wire of the external circuit is carried by electrons.
Flow of electrons
Zinc anode
Copper cathode
Porous cup
Flow of anions
Zinc sulphate solution
Also...
Copper sulphate solution
The natural voltage of a Daniell cell using zinc and copper is 1.1 volts. The voltage of a dry cell (page 14) is 1.5 volts. Other combinations of elements produce their own unique natural voltages.
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