260 Dr. Schoenbein's yw/ ///tv Observations 



sume of water ; according to my experiments this metal is sen- 

 libly dissolved by nitric acid diluted with 1000 times its vo- 

 lume of water. As it is evident that the different action of 

 she same nitric acid on iron is caused by a certain electrical 

 late of the metal, I endeavoured to ascertain its nature by 

 making an iron wire the positive pole of a voltaic battery set 

 in action by nitric acid. I experimented in the following 

 manner : 



Nitric acid, of sp. gr. 1*36, at the ordinary temperature, was 

 used in a circle of 15 plates, with a voltaic cup apparatus; at 

 the positive pole an iron wire, and at the negative a platina 

 wire, dipped into the acid. When I closed the circuit with 

 the negative wire, the iron wire was acted upon as usual ; 

 when 1 closed it with the iron wire, by first dipping one end 

 in the nitric acid, and then making the other end the positive 

 pole of the battery, the same effect also took place ; but when 

 I closed the circuit so that one end of the iron wire was first 

 united with the positive pole, and the other end afterwards 

 dipped into the acid, no action took place on the iron, and it 

 possessed, after its separation from the positive pole, all the 

 properties which it had by heating, or when protected by gold 

 and platina, — precisely those which I have already so fully 

 stated in my former paper. I heated the nitric acid used in 

 the circuit to nearly its boiling point before it acted upon the 

 positive iron wire. It follows, of course, that under these cir- 

 cumstances the water contained in the nitric acid was decom- 

 posed. No hydrogen gas is given out at the negative pole 

 iiom strong nitric acid, for instance, of sp. gr. 1'36, but it 

 combines with a part of the oxygen of the acid, and converts 

 the latter into nitrous acid. 



At a temperature of 70° centigi'ade, a gas is given out at the 

 negative platina wire, which I have not yet particularly exa- 

 mined, but which is probably deutoxide of nitrogen. It has 

 hitherto been considered that the other element of the water, 

 the oxygen, combhies with the positive iron wire, and forms a 

 hydrate with the nitric acid. 



If the circuit is so formed that the nitric acid has no action 

 upon the iron wire, the free oxygen does not combine with 

 tiie metal, but is given off in a gaseous state, precisely as when 

 silver, gold, or platina wires are used. This is not only the 

 case with acid of the above strength, but also with acid diluted 

 with I, 10, 100, and even 400 times its volume of water. 

 That the iron is not partially oxidated is evident from its un- 

 changed metallic lustre, as also from the proportions of gas 

 given off at both wires, which I found according to several 

 measuremenis to be as 1 to 2. If the two wires where the 



