Electromotive Forces in a Voltaic Cell. 



373 



a special action of its constituents. Since the constituent CI 

 is liberated where the + current enters the liquid, and H 

 where the negative enters, we suppose that each equivalent of 

 CI in the compound HC1 is charged with a definite quantity 

 of negative electricity, which conditions its attraction for the 

 opposite positive electricity. It is the electro-negative element 

 of the compound. So also must the equivalent H be charged 

 with + E and form the electro-positive element. These 

 charges could be produced by the combination of H and CI 

 exactly in the same way as they are produced by the contact 

 of zinc and copper. Since the HC1 formed is unelectrifled, 

 we must suppose that atoms of the + and — constituents 

 contain equal quantities of + and — E. 



" If now we immerse a Zn and a Cu plate into the dilute 

 HC1, we can conjecture that the zinc has a stronger attraction 

 for the electro-negative constituent (CI) than for the H. In 

 consequence of this the molecule of HC1 touching the zinc 

 will so lay itself that its electro-negative element is near the 

 zinc and its electro-positive element near the copper. At the 

 same time the molecules thus polarized act by electrical attrac- 

 tion on the constituents of the successive molecules of HCI, 

 arranging the whole row of molecules between the Zn and the 

 Cu plates as in the figure. 



Zinc 



fig/pet. 



CI. H 



31 



a. s 



JIE 



Gl.H 



IV 



a. h: 



0© 0© 0© 0© 



" By induction the negative electricity of the zinc-touching 

 electro-negative constituent, chlorine, would act on the E in 

 the zinc in such a way that the near parts will charge them- 

 selves positively, the further parts negatively. In the same 

 way the copper adjacent to the electro-positive element (H) 

 of the HCI atom lying against it will receive negative elec- 

 tricity. The positive will remove itself to the remoter regions. 



" Thereupon the positive electricity in the zinc would com- 

 bine with the negative of the next-lying CI atom, and this 

 latter with zinc to form unelectrical ZnCl. The electro-positive 

 atom H which was formerly joined to that CI atom would itself 

 unite with the neighbouring atom of CI belonging to the second 



