of Iron and Bismuth. 



49 



acid none of these methods have a similar effect : indeed, by 

 associating iron wire with platina, and immersing it in a glass 

 of nitric acid sp. gr. l-l-t, I have frequently observed the 

 action to be increased ; but though the peculiar state is not 

 called forth by direct association with platina, it is when the 

 vf'wQ is connected with that metal in a certain manner through 

 the medium of a galvanometer; in proof of which I beg to 

 call the attention of Dr. Schcenbein and other readers of the 

 Philosophical Magazine who may be interested in the subject 

 to the following facts, by which also it will, I think, be 

 shown, that when in the peculiar state it is absolutely incapable 

 of conducting voltaic electricity in a low state of intensity. 



1, 2, 3, represent three glasses half 

 filled with diluted nitric acid : from 

 1 proceeds a platina wire connected 

 with one of the mercury cups of a 

 delicate galvanometer, and from 3 an 

 iron wire of equal length, and dipping 

 into the other cup ; the glasses are 

 connected by bent iron wires. Now, 

 in acid of this strength (sp. gr. 1*14? 

 or r2), iron wire, however thickly 

 coiled with platina or with any 

 other metal that I have tried, is 

 strongly acted on, the brown oxide 

 being instantaneously and copiously deposited ; neither is the 

 action prevented if the platina is associated with its upper end, 

 and dipped into the acid in such a manner that the point of 

 junction shall be above the surface of the fluid: but if the 

 platina wire is connected with the galvanometer, and im- 

 mersed in the glass of acid, and the iron wire united^rs^ with 

 the instrument^ and then dipped into the acid, it is brought to 

 the peculiar state^ and is not in the slightest manner acted on 

 in any length of time, nor does the galvanometer evince any 

 signs of electrical action. Any other mode of completing the 

 circuit is ineffectual, but 3 or 4 glasses containing a similar acid 

 may be united by bent pieces of wire, as shown in the sketch, 

 with a result similar to that when a single glass is employed. 

 This very interesting experiment is one of delicacy, and 

 without the following precautions will generally fail. 1st, The 

 wire must be in its natural state, any attempt to clean the 

 surface by scraping or filing destroys the peculiarity ; one drop 

 of acid touching the surface previous to immersion does the 

 same. In repeating the experiments lately before a number 

 of persons, I continually failed in exhibiting the phaenomena, 

 till I observed that the pliers with which I cut and bent the 

 Fhil. Mag, 5. 3. Vol. 12. No. 7 1 . Jan. 1 838. H 



