The convention of signs for a galvanic cell

We observe that no term on the right-hand side is dependent upon an electrical potential. In actual practice only one solution is used. There are concentration gradients of hydrogen and silver chloride within the solution, but the effect of the hydrogen and silver chloride on the chemical potentials of the hydrogen and chloride ions is small and negligible. 

Cells in which only one electrolytic solution is used are called cells without liquid junction. Cells in which it is necessary to use two solutions with a boundary between them are called cells with liquid junction. Such cells are discussed in Section 12.12. 

Equation (12.31) relates the emf of a cell to the change of the Gibbs energy for the change of state, based on n faradays, that takes place within the cell when the leads are short-circuited. The change of state is spontaneous, the value of AG is negative, and therefore the emf is positive. We conclude that the emf of any actual cell is always positive. However, the representation of a cell may be written in two ways. For the particular cell that we have been discussing, we may depict it as either 

Conventions have been established to obviate these difficulties. For any 

The convention discussed here is consistent with those adopted by the Physical Chemistry Section of the Commission on Physico-Chemical Symbols and Terminology of IUPAC in Stockholm, 1953 i.e., the Stockholm Convention. See Christiansen, A. (1960). J. Am. Chem. Soc., 82, 5517. 

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