808 Mr. H. Smith on the Spectroscopy of the Electric 



wires fused into glass tubes with the protruding ends filed 

 flush with the glass. When these electrodes were connected 

 to the terminals of an electric machine, an electrolytic 

 mixture of hydrogen and oxygen was evolved at each pole 

 in equal quantities. Faraday repeated the experiment *, and 

 found that if a nail was substituted for one electrode no gas 

 was evolved at the nail, while the evolution of gas at the 

 unaltered electrode was the same as bef<re. A spark-gap 

 placed in series with the cell caused a larger evolution of gas 

 for the same number of turns of the machine, the longer the 

 spark-gap the greater being the evolution of gas. In a 

 solution of sodium sulphate, however, even with powerful 

 sparks, he obtained very little gas. In Table II. I give some 

 results obtained in the case of the brush. The gas evolved 

 in all cases was explosive. 



Liquid. 

 H,0 .... 



•05 p. c. / 







Table II. 







Sign of 

 Brush. 



+ 



Current in 

 rnilliamps. 



11-9 



Potential 

 in volts. 



2500 



Vol. of gas 



liberated 



per luin. (A). 



(N.T.P.j 



•63 c. c. 



Vol. of gas 



calculated (B). 



(N.T.P.) 



•041 c.c. 



Eatio 

 A/B, 



15-3 



- 



5-7 



4250 



•55 „ 



•039 „ 



14-1 



+ 



32-3 



700 



L55 „ 



•112 „ 



13-8 



— 



33-9 



300 



•29 „ 



•236 „ 



1-23 



In distilled water fifteen times as much gas is evolved as 

 can be accounted for by electrochemical decomposition. 

 When the cell forms part of a condenser and spark-gap 

 circuit, the evolution of gas is considerable and out of all 

 proportion to the quantity which should be evolved by the 

 action of the current. 



In solutions, with the uncondensed brush, the evolution of 

 gas is much more considerable at the positive point than at 

 the negative, the evolution at the negative being little more 

 than the calculated amount. Taking this into account with 

 the harsher noise of the positive brush and its intermittent 

 character as shown in the rotating mirror, it would seem 

 thai the positive brush consists of a series of small sparks, 

 while the negative brush bears a closer resemblance to an 

 arc. Some of the spectra occurring at the negative brush 

 are either characteristic of an arc or of a type intermediate 

 between the arc and spark. 



* Faraday's Exp. Res. vol. i. §§ 327-331. 



