Decomposition of Water by the Galvanic Battery. 77 



sition of water than by getting the gases into separate vessels, 

 and then mixing them in the proper proportions. With half a 

 dozen of cells of the cast-iron battery, a voltameter, a pair of 

 gas bags, and the apparatus just described, the gas microscope 

 and polariscope, as well as the dissolving views, may be exhibited. 

 But the experimenter must, until he acquires experience, proceed 

 with great caution. 



The second result was a new voltameter, to which a common 

 jet may be screwed, and the mixed gases inflamed as they issue 

 from it without the slightest risk of injury, and by which the full 

 decomposing power of a battery of 100 or 500 cells arranged in 

 one series may be exerted without exhausting the power of the bat- 

 tery more rapidly than if it consisted of three or four plates. This 

 voltameter is new in every respect, — in the material of which it is 

 made, in the manner in which the electrodes are connected with the 

 opposite ends of the battery whilst the vessel remains air-tight ; 

 new in the metallic plates employed as electrodes, and in the ai'- 

 rangement of these plates ; finally, new in the fluid which is used 

 for the decomposition. After having succeeded in making the ap- 

 paratus for preventing dangerous explosions, I found that a glass 

 vessel was totally unfit for a voltameter such as I wanted : first, 

 because it is extremely difficult to make a glass vessel permanently 

 air-tight ; secondly, because it is not sufficiently strong to bear 

 the pressure of the coudensed gases; thirdly, because on one 

 occasion, by unscrewing a bag which I had filled with the mixed 

 gases, a spark which was produced by accidentally breaking con- 

 nexion with the battery, or by the contact and separation of the 

 electrodes, inflamed the gases and caused an explosion which 

 shattered the vessel. I fortunately escaped unhurt. The vessel 

 which I have used for nearly the last two years is made of wrought 

 iron about an inch thick. Its form is cylindrical, its height 

 about 16 inches, and its inside diameter 6 inches. It is open 

 at the top, which was turned flat in a lathe ; the bottom is laid 

 on a circular piece of wood, which is placed on an iron plate 

 about |ths of an inch thick and 8 inches square. On the top 

 of the vessel is laid a thick collar of vulcanized India-rubber, 

 and on this an iron plate similar to the one under the bottom. 

 In the top plate there are two holes, to one of which a stopcock 

 is adapted ; to the other is fitted, air-tight, a perforated piece of 

 brass which projects about an inch and a half above the plate. 

 The hole in this brass is large enough to admit a thick wire. 

 The upper part of the brass is tapped in order that a brass cap 

 may be screwed to it, to prevent the escape of the gases through 

 the hole. When the electrodes are placed in the vessel, one of 

 them is connected by solder or pressure with the inside; to the 

 other is soldered or riveted a copper wire, which passes through 



