250 & P. Sharpies on some/omis of the Oalvamc Batiery. 



sulphuric acid, and enough water added to take up the precipi- 

 tated chromic acid. This formed the most satisfactory battery 

 tried ; it was perfectly constant during twelve hours. The in- 

 ternal resistance was only about 1^ times that of an ordinary 

 Bunsen's cell of the same construction, and not the slightest 

 odor could be perceived in the room. The electro-motive force 

 was the same as that of the Bunsen cell. 



Ex. No. 8. Having seen in the American Chemist* a notice 

 of a new battery by Prof. Bunsen, mentioned in an address hy 

 Prof. Roscoe, before the Chemical Section of the British Asso- 

 ciation for the Advancement of Science, I made a trial of it 

 This battery consisted of two metals, platinum and 2dnc, with a 

 single fluid, namely, a solution of chromic acid in dilute sul- 

 phuric acid ; I tried it in a small cell in which equal surfaces of 

 zinc and carbon were opposed to each other. The electro-mo- 

 tive force was twice that of a Daniell's cell, or 1-2 that of a 

 Bunsen's ; but it was not very steady, and the chromic acid 

 acted strongly on the zinc. 



Ex. No. 9. Dr. Gibbs suggested to me to try a solution of 

 chromic acid in nitric acid in the porous cell, using sulphuric 

 acid in contact with the zinc. The electro-motive force was the 

 same as in the last experiment, and the internal resistance was 

 the same as in the Bunsen cell. The battery was perfectly con- 

 stant. Two cells very slowlv decomposed pure water and gave 

 vivid flashes of light when the connections were made. 



Ex. No. 10 was undertaken to determine the effect of re- 

 placing the bichromate by manganic oxide. The porous ceu 

 was filled around the carbon with manganic oxide; nitric acia 

 was then poured on it until it was completely saturated, l^b 

 gave verv poor results ; the electro-motive force was about r* 

 times that of a Daniell's cell. The battery was not veiy steaay 

 and after running some time began to give off fumes of nitrous 



Ex. No. 11. Joulef gives an experiment with a battery in 

 which platinum in nitric acid is used as the negative, and zin 

 in caustic potassa as the positive electrode, and gives the eiej 

 tro-motive power as equal to 241 Daniell's. I repeated tnee^.^ 

 periment, using a solution containing \ of its weight of P^^- 

 hydrate in the outer cell, and a saturated solution of ctirou 

 in nitric acid in the inner cell. I found the electro-motive ton _ 

 at first about 2-35 that of Daniell's cell, the internal resisiau 

 being that of a Bunsen's cell. It was rather unsteady at n - 

 and then began to gradually decline. No odor was percep u ' 

 . Several experiments were tried, with the hope of obtaining 

 single fluid battery with the following results. ^^^e 



Ex. No. 12. A strong solution of caustic po*^^^- the cell 



saturnted with ferricyanide of potassium and used m ^^^ 



* Vol. i, p. -.'09. f Phil. Mag , vo'. xiiv. p. H^. 



