404 



TENTH ANNUAL REPORT OF 



Fig. 31. 



A varnished metallic cover is fastened air-tight on the glass jar a. 

 This cover has three openings ; the glass tubes b and c pass air-tight 

 through two of them. The third is somewhat larger and can be closed 

 by a stopper. Each of the tubes is 30 centimetres long and 1.8 centi- 

 metre in diameter. At the upper end of each tube a platinum wnre 

 is fused into the glass, having at the top a cup tor mercury, and to 

 the other end of the wire a platinized platinum plate is soldered, 

 which extends nearly to the lower end of the tube. 



The following is the process for charging such an element : Fill 

 the vessel a with water, through the opening d; close c? and then 

 invert the whole apparatus ; in this way the tubes b and c are filled 

 with water. After restoring the element to an upright position, pass 

 through the opening d the connecting tube of the gas apparatus. 

 One of the tubes is filled in this way with hydrogen, and the other 

 with oxygen to about f the entire length. 



Fig. 30 represents a wooden trough intended to hold four such 

 elements ; it is exhibited on a scale one-fourth of that of Fig. 29, The 

 elements being in position, the small mercury cups are connected by 

 cop])er wires ; into the last cup to the left a w^re passes from the 

 binding screw r, and into the last cup to the right, one from the 

 binding screw s. The poles u and v are fixed in the two binding 

 screws. 



This form of the gas battery is almost exactly the same as that 

 which Grrove describes as the most convenient, in the 

 appendix to a memoir : "Ore the voltaic gas batterij, 

 its application to endiometry ." (Phil. Trans. 1843, 

 Pt II, page 51 ; Pogg. Ann. im Erganzungband II, 

 1848.) Tlie arrangement, however, described in the 

 memoir, admits of the removal of the tubes for the 

 punpose of examining the gases. 



For this purpose the tubes b and c must not be 

 cemented into the cover of the vessel a, but they must 

 be inserted through corks so that they can be removed 

 and replaced at pleasure. Fig, 31, represents the 

 ■ ' h arrangement indicated by Grove in the above cited 

 I V V^V^'"' 5 « ci is a glass vessel like a Woulfe's bottle ; 

 " j; ^ !| the middle opening is closed by a glass stopper ; the 



] glass tubes are adapted to the other openings by 



' ground collars, 



§ 44. TJieory of the gas battery. — Schonbein has set forth his views 

 on this subject in two memoirs in Poggendorff's Annalen ; the first 

 in volume LVIII, page 361 ; the second in volume LXXIV, page 

 241. 



His view is, 'Hhat the hydrogen, in the above described arrange- 

 ment, with reference to the generation of tlie current, plays a primary, 

 and the oxygen only a secondary or depolarizing part," 



The hydrogen alone is certainly able to generate a current of polari- 

 zation, as Schonbein's experiments (in section 39) prove. A platinum 

 plate, immersed but a short time in an atmosphere of hydrogen, gives, in 

 combination with a clean platinum plate, a current, even if the liquid 



o 



1) 



