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 <J : ;;^jg KCl I AgCl AgCl Ag.
The principal action in this case would be that m gram- molecules of the salt would be transported from the concen- trated to the dilute solution. In a similar way we should calculate the electromotive force by means of the ex- pression —
��r^ ^T
��J jmdi+ j7nid In c > volts.
��71.23,070 ,
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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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