Mr. Faraday on a peculiar Voltaic Condition of Iron. 63 



which though it does not adhere closely still is not readily dis- 

 solved by "he acid when the connexion with the battery is 

 broken, but remains for many hours on the iron, which itself 

 is in the peculiar inactive state. If the power of the voltaic 

 apparatus be very weak, the coat of oxide on the iron in the 

 nitric acid often assumes a blue lint like that of the oxide 

 formed by heat. A part of the iron is however always dis- 

 solved in these cases. 



If it be allowed that the surface particles of the iron are 

 associated with oxygen, are in fact oxidized, then all the other 

 actions of it in combination with common iron and other 

 metals will be consistent; and the cause of its platina-like 

 action, of its forming a strong voltaic current with common 

 iron in the first instance, and then being thrown into action 

 by it, will be explained by considering it as having the power 

 of determining and disposing of a certain portion of hydrogen 

 from the electrolyte at the first moment and being at the same 

 time brought into a free metallic condition on the surface so 

 as to act afterwards as ordinary iron. 



I need scarcely refer here to the probable existence of a 

 very close connexion between the pheenomena which Professor 

 Schoenbein has thus pointed out with regard to iron, and those 

 which have been observed by others, as Ritter and Marianini, 

 with regard to secondary piles, and A. De la Rive with respect 

 to peculiar affections of platina surfaces. 



In my Experimental Researches (par. 476.) I have recorded 

 a case of voltaic excitement, which very much surprised me 

 at the time, but which I can now explain. I refer to the fact 

 stated, that when platina and iron wire were connected vol- 

 taically in association with fused nitrate or chloride of silver, 

 there was an electric current produced, but in the reverse di- 

 rection to that expected. On repeating the experiment I 

 found that when iron was associated with platina or silver in 

 fused nitrate or chloride of silver, there was occasionally no 

 current, and when a current did occur it was almost con- 

 stantly as if the iron was as platina, the silver or platina 

 used being as zinc. In all such cases, however, it was a 

 thermo-electric current which existed. The volta-electric 

 current could not be obtained, or lasted only for a moment. 



When iron in the peculiar inactive state was associated with 

 silver in nitric acid sp. gr. 1-35, there was an electric cur- 

 rent, the iron acting as platina ; the silver gradually became 

 tarnished and the current continued for some time. When 

 ordinary iron and silver were used in the nitric acid there was 

 immediate action and a current, the iron being as zinc, to the 

 silver as platina. In a few moments the current was reversed, 



