Page:Text-book of Electrochemistry.djvu/230

 end solutions must be equal to the sum of all the d V values for the various contiguous solutions, and therefore —

V=- -^^- i f(l - m)di + f(l-m)edJlnc] volts, n. 23,070 1/^ ^ }/ ^ )

' Co Co

If we had used a concentration element of the following composition —

��dll. tol. cone. Bol.

Ag AgCl AgCl I KCl I KCl KCl | AgCl Ag Ag

where the unpolarisable electrodes are of the second order, and if n. 96,500 coulombs were conducted through the combi- nation in the direction indicated, we should have found the following result : —

Ag Ag AgCl i KCl ^^^1 I  volts.

��71.23,070 ,

' Co Co

In the example given n = 1 (for KCl). In concentration elements with unpolarisable electrodes of the second order, the electromotive force strives to drive the current through the liquid from the concentrated to the dilute solution ; with unpolarisable electrodes of the first order the current is driven in the opposite direction. (It is assumed that m is a proper fraction, which is generally the case : see pp. 137 and 143.)

Elements of the latter kind have recently been exactly studied by Jahn (1?). The liquids used were dilute

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