Phase boundary line notation

More generally, a battery consists of two electrodes separated by at least one electrolyte phase. A convenient notational representation of a battery is to write the chemical composition of the phases composing it in the order in which the phases are connected, and to indicate each phase boundary by a vertical line. A double vertical line indicates the contact zone of two electrolyte phases. 

A single vertical line represents a phase boundary. For example, Zn(s) Zn iaq) indicates that the solid Zn is a different phase from the aqueous Zn " ". A comma separates the half-cell components that are in the same phase. For example, the notation for the voltaic cell housing the reaction between I and Mn04 shown in Figure 21.6 is... 

Because there are so many possible electrochemical cells, a shorthand notation for representing their specific chemistry has been devised. This cell notation lists the metals and ions involved in the reaction. A vertical line,, denotes a phase boundary, and a double line, H, represents the salt bridge. The anode is always written on the left, and the cathode on the right ... 

In this notation a phase difference (boundary) is indicated by a single vertical line. Thus, in this case, vertical lines occur between the solid Mg metal and the Mg in aqueous solution and between solid Al and in aqueous solution. Also note that the substance constituting the anode is listed at the far left and the substance constituting the cathode is listed at the far right. 

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