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XVIII. On Galvanic Circuits in which Perchloride of Iron enters 

 as an Element. By Professor Buff*. 



SOLUTION of perchloride of iron has, as far as I know, not 

 hitherto been used as a liquid conductor in the formation 

 of galvanic circuits. The facility with which this body furthers 

 the oxidation of hydrogen and the eleotro-positive metals, com- 

 bined with the possibility of producing it at a cheap rate, led to 

 the supposition that it might be very advantageously used as an 

 element in a constant electric circuit. Occasional observations 

 which Liebig had made appeared to confirm this supposition, 

 and gave rise to the following investigation of the subject. 



The first experiments, made with a very pure, almost neutral 

 perchloride of iron, did not answer the expectations formed. 

 An ordinary charcoal zinc pair was used, in which nitric acid 

 was replaced by solution of perchloride of iron of syrupy consist- 

 ence. To measure the current, a tangent galvanometer was em- 

 ployed, the simple ring of which was 200 millims. in diameter. 

 A stream regulator was inserted in order to obtain currents of 

 different intensities. It was found that even the weakest, which 

 only just produced an action on the needle, showed no constancy. 

 At the same time the charcoal was covered with metallic iron 

 mixed with oxide of iron. 



Metallic iron dipped in solution of perchloride changes it, as 

 is well known, into protochloride, being at the same time dis- 

 solved. This occurred with the iron deposited on the charcoal 

 when allowed to stand some time in the solution. During the 

 progress of the electric decomposition the time was too short for 

 this ; the charcoal polarized itself with the iron, and no constant 

 current could result. 



When the neutral, saturated solution of perchloride was de- 

 composed between platinum poles, chlorine was received at the 

 positive pole. At the negative pole iron was deposited in minute, 

 hard, crystalline laminae, accompanied by a very scanty evolution 

 of hydrogen. With platinum poles of greater dimensions, the 

 hydrogen disappeared. A small addition of hydrochloric acid 

 to the solution prevented the deposition of the iron perfectly, 

 even with a current of considerable strength. Hydrogen was 

 only perceptible v. aen the negative pole had a comparatively 

 small surface. On the other hand, the evolution of hydrogen 

 increased as soon as the solution was much diluted with water. 



The perchloride, in a concentrated solution containing hydro- 

 chloric acid, does not appear to be electrolyzed. Its presence 

 aeenis to serve- only to convey fresh chlorine to the hydrogen 

 separated from the hydrochloric acid. As long as this occurs 



* From the Avnaltn der Chemie und Pharmacie, vol. xcii. p. 117. 



