Page:Text-book of Electrochemistry.djvu/38

 ". GROTTHUSS CHAIN.

��made in it. Nevertheless, it has played an extremely important part in the development of the science, and has been introduced here, as it has to a certain extent an orien- tating character. It is hardly connected with the subject of electricity, but must rather be regarded as an attempt to represent the chief facts of " Berzelian " chemistry.

The Grotthuss Chain. — It became necessary to explain why the ions were only separated at the poles by the electric current. It was at first believed (Eitter) that hydrogen was formed by the union of water with negative electricity, and that oxygen resulted from the combination of water with positive electricity. In 1805, Grotthuss brought forward the view that the molecules of an electrolyte arrange themselves polarly so as to form a chain :

��according to this hypothesis, which

gained credence for a long time, j^^

all the dissolved molecxdes in a ^iq, 4,

potassium chloride solution take

up such a position that their positively charged potassium

sides are towards the negative electrode, and the chlorine

sides towards the positive electrode (see Fig. 4).

During the electrolysis the positive potassium atom next the negative electrode, and the negative chlorine atom next the positive electrode, are separated. The chlorine of the first molecule combines with the potassium of the molecule next ity and this new molecule now turns so as to take up a position similar to that of the original molecule. An analogy drawn by Grotthuss, as well as by Davy and Faraday, con- ceived the electrodes as doors through which the two elec- tricities entered into the liquid, and there combined with the nearest ions, whereupon the other ions between the electrodes then rearranged themselves.

The Grotthuss view, however, cannot be correct, for in a cylindrical column of liquid the electrical force acts equally at all parts (the fall of potential per centimetre drives the charged ions ; compare p. 6).

Ampere's Theory, — Contrary to Davy and Berzelius,

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