Definite Chemical Action of Electricity. 341 



copper plate, which dipped into the acid of the second basin, 

 was connected with the negative electrode of the frst basin ; 

 and a platina plate, which dipped into the acid of the third 

 basin, was connected with the negative electrode of the second 

 basin. The negative electrode of the third basin was con- 

 nected with a volta-electrometer (711.), and that with the 

 negative end of the voltaic battery. 



809. Immediately that the circuit was complete, the electro- 

 chemical action commenced in all the vessels. The hydrogen 

 still rose in, apparently, undiminished quantities from the po- 

 sitive zinc electrode in the first basin. No oxygen was evolved 

 at the positive copper electrode in the second basin, but a 

 sulphate of copper was formed there; whilst in the third basin 

 the positive platina electrode evolved pure oxygen gas, and 

 was itself unaffected. But in all the basins the hydrogen li- 

 berated at the negative platina electrodes was the same in 

 quantity, and the same with the volume of hydrogen evolved 

 in the volta-electrometer, showing that in all the vessels the 

 current had decomposed an equal quantity of water. In this 

 trying case, therefore, the chemical action of electricity proved 

 to be 'perfectly definite. 



810. A similar experiment was made with muriatic acid 

 diluted with its bulk of water. The three positive electrodes 

 were zinc, silver, and platina; the first being able to separate 

 and combine with the chlorine without the aid of the current; 

 the second combining with the chlorine only after the current 

 had set it free ; and the third rejecting almost the whole of it. 

 The three negative electrodes were, as before, platina plates 

 fixed within glass tubes. In this experiment, as in the former, 

 the quantity of hydrogen evolved at the cathodes was the same 

 for all, and the same as the hydrogen evolved in the volta- 

 electrometer. I have already given my reasons for believing 

 that in these experiments it is the muriatic acid which is di- 

 rectly decomposed by the electricity (764-.); and the results 

 prove that the quantities so decomposed are perfectly definite 

 and proportionate to the quantity of electricity which has 

 passed. 



811. In this experiment the chloride of silver formed in the 

 second basin retarded the passage of the current of electricity, 

 by virtue of the law of conduction before described (394-.), so 

 that it had to be cleaned off four or five times during the 

 course of the experiment; but this caused no difference be- 

 tween the results of that vessel and the others. 



812. Charcoal was used as the positive electrode in both 

 sulphuric and muriatic acids (808. 810.); but this change 

 produced no variation of the results. A zinc positive elec- 



