Fluid Galvanic Battery. 261 



tery in which there would be no need of porous cells or nitric 

 acid, and which, with a moderate number of plates, would pro- 

 duce a brilliant coke light or lime light. From experiments made 

 with our large galvanometer on the voltaic power of a pair of 

 zinc and platinized coated iron plates excited by dilute sulphuric 

 acid, I inferred that a battery containing a hundred, or one 

 hundred and fifty such plates, would produce the light which I 

 required. Having more than twenty Wedgwood troughs, each 

 containing ten cells, I saw that the cost of such a battery would 

 be very moderate : I therefore resolved to make one of 200 pairs 

 of plates. Whilst the battery was being made, I occasionally 

 tried the power of one trough or ten cells. I first used a solu- 

 tion of sulphuric acid consisting of one part of strong acid and 

 about seven of water. I then tried one part of the same acid 

 mixed with about six times its bulk of a pretty strong solution 

 of common salt. The addition of the salt produced a consider- 

 able increase of voltaic power. I next employed an exciting 

 mixture consisting of one part of nitric, six of sulphuric acid, 

 and about fifty of water. With this mixture, ten pairs of plates, 

 each about 6 inches square, ignited a pair of coke-points, which 

 gave a small but brilliant star of light. But the nitric acid gra- 

 dually dissolved the alloy of lead and tin with which the iron 

 plates were coated, and the platina powder fell off. I then tried 

 one part of nitric acid, twelve of sulphuric, and about a hundred 

 of water. This mixture also acted on the coating of the iron 

 plates. I was therefore obliged to give it up, and'to return to 

 the solution of sulphuric acid and common salt. 



Before the entire battery was finished, I tried the power of 

 100 cells in igniting a pair of coke points. I was greatly dis- 

 appointed by- the feeble illuminating power of the coke light, 

 and began to examine whether any of the cheap negative metals 

 could be advantageously used with an exciting fluid which would 

 contain a small portion of nitric acid. One of the first which 

 occurred to me was cast iron, which acted so well as the negative 

 element of the nitric acid battery. I prepared a cast-iron cell 

 of the nitric acid battery, and a zinc plate, which I separated 

 from the iron by pieces of wood. The cell was filled with one 

 part of nitric, six of sulphuric acid, and about fifty of water. The 

 galvanic action was very powerful, but the zinc plate was soon 

 covered with a deposit of nitrate of iron. It was evident, then, 

 that cast iron and zinc could not be excited witli any fluid 

 containing nitric acid unless the two metals were separated by a 

 porous cell. I then tried the same cast-iron cell and zinc plate 

 excited with one part of sulphuric acid and seven of water. The 

 galvanometer showed that the voltaic current was very feeble. 

 I therefore gave up all hope of making a battery such as I 



