Decomposition of Water by the Galvanic Battery. 83 



of potash, soda, or ammonia in a quart of water. If there be 

 moi-e than an ounce and a quarter to each quart of water, the 

 quantity of foam will be very considerable ; if there be less than 

 an ounce, the conducting^ power of the solution will not be suffi- 

 cient, and the quantity of the gases produced will be greatly 

 diminished. 



For either of the two arrangements of the electrodes I have 

 described, a cylindrical vessel does not answer well. For them 

 a prismatic vessel having a rectangular bottom is the most con- 

 venient. The inside of the iron vessel should be coated with an 

 alloy of lead and tin, or of lead, tin and antimony, in which the 

 proportion of tin, or of tin and antimony, is small, — first, in order 

 to preserve it from rust; secondly, to protect it against the 

 action of sulphuric acid, and thus render it fit for a voltameter, 

 in which the positive electrode is platina ; the negative one, tin 

 plates coated with an alloy of lead and tin ; and the fluid through 

 which the voltaic current passes is dilute sulphuric acid. The 

 coated sides of the vessel may be the negative electrode. AVith 

 an iron voltameter such as I have described, the mixed gases 

 may, without the slightest danger, be inflamed as they are pro- 

 duced by the decomposition of water, and a constant and bril- 

 liant lime light may be obtained. 



The third result is a new negative element, cheaper, more 

 durable, and one which may be made to act with greater power 

 than the platinized silver used in Smee's battery. It is sheet 

 tin, coated with an alloy of lead and tin, in which the propor- 

 tion of tin is not greater than that of lead, or of lead, tin and a 

 small quantity of antimony. On tin plates thus coated, the 

 dilute sulphuric acid commonly used in Smee's battery will 

 scarcely exert any action. It -may be platinized like sheet silver ; 

 or it may be coated with borax, and will then answer as well, or 

 veiy nearly as well, as if it were platinized. It is evident that 

 tin ])lates thus prepared arc far cheaper and more durable than 

 platinized silver ; and because they can be brought nearer than 

 platinized silver to the zinc plates without danger of touching 

 them, they may be made to act with greater power. 



The fourth result is a new means of protecting iron against 

 the action of the weather and of various corroding substances, so 

 that iron thus vrotected will answer for all the purposes to which 

 sheet lead and galvanized iron are ajjplied. Besides the experi- 

 ments by which I have proved the superiority of tin plates (that 

 is, of sheet-iron j)lates), coated with an alloy of lead and tin, 

 over leaden ones, as tlie electrodes of a voltameter, I have made 

 many others, in order to compare the action of concentrated 

 nitric, sulphuric and muriatic acid, as well as of dilute sulphuric 

 and mui'iatic acid on lead and galvanized iron, with their action 

 on iron coated with an alloy of lead and tin, in which the quan- 



