S. p. Sharpies on some forms of the Galvanic Battery. 251 



employed in experiment No. 8. This gave a feeble current and 

 the carbon was rapidly polarized. 



Ex. No. 13. As solutions of sulphurous acid and acid sul- 

 phites dissolve zinc without evolution of hydrogen, forming 

 hyposulphites, it was thought that these might be used as the 

 exciting liquids. They gave a very feeble current and the car- 

 bon was soon polarized ; the sulphite of zinc formed also adhered 

 to the zinc and prevented further action. 



Ex. No. 14. Iodide of potassium saturated with iodine was 

 tried ; this also gave a feeble current and the carbon soon be- 

 came polarized. 



Ex. No. 15. A cell of the Maynooth battery was fitted up 

 and a saturated solution of potassic bichromate in nitric acid used 

 as the absorbing liquid ; the battery was not very constant, and 

 the iron was soon attacked ; no fumes, however, were given off 

 The electro-motive power was about -55 of a Darnell's cell 



The result of these experiments seem to show that the bat- 

 tery used in experiment No. 7 is the best for ordinary use, 

 since it costs but little, if any more, than the Bunsen battery 

 charged with nitric acid alone, and is entirely free from fumes 

 iintil exhausted. If the following directions are observed in 

 preparing the fluids, it cannot fail, I think, to give satisfaction. 

 . To prepare the exciting liquid, sulphuric acid of 1-84 sp. gr. 

 IS mixed with nine times its volume of water and allowed to 

 stand until the precipitated lead has all settled. The clear acid 

 IS then decanted and is fit for use. This plan of preparing the 

 acid has been in use in this laboratory for some years and 

 gives very good results, local action being almost entirely pre- 

 vented by the removal of the lead. 



lo prepare the absorbing fluid, ordinary commercial nitric 

 acid is saturated with potassic bichromate ; this should be done 

 m a warm room, as it takes up much more when warm than 

 Jhen cold. The solution thus prepared is mixed with one- 

 hird of its volume of sulphuric acid and enough water added 

 re-dissolve the chromic acid precipitated. 

 >wo objects are gained by adding the sulphuric acid. The 

 inixture is less expensive than if pure nitric acid is used and 

 ^ne internal resistance is decreased. If the internal and exter- 

 ^r ^®^l3 are properiy proportioned this battery will run until 

 ^^e excitmg fluid is exhausted, without giving ofi-any fumes of 

 nitrous acid. If crude chromic acid could be obtained at a 

 suniciently low rate. No. 9 would be a very powerfiil and con- 

 cement battery for many purposes. , ^, 



% thanks are due to Dr. Wolcott Gibbs for many valuable 

 J^Sff tions made during the progress of this investigation and 

 I ^be use of the apparatus employed. 



Cambridge, Jan. 17, I87i. 



• JoDK. Sci. -Third Series, Vol. I, No 4. -April, 1871. 



