1893.] 



The Electrolysis of Steam. 



91 



produced by the sparks. We should not expect to find any simple 

 relation between the amount of decompositions from these causes and 

 the quantity of electricity which had passed through the gas. The 

 hydrogen and oxygen produced by such causes would, however, be 

 driven up the tube in chemically equivalent proportions, and could 

 therefore be eliminated by sending a spark through these gases, when 

 they would recombine and form water. 



When the sparking had ceased, the gases which had collected in the 

 test-tubes e and e were analysed ; in the first place they were exploded 

 by sending a strong spark through them ; this at once got rid of the 

 hydrogen and oxygen which existed in chemically equivalent propor- 

 tions, and thus get rid of the gas produced by heat, &c, along the 

 length of the spark. After the explosion, the gases left in the tubes 

 were the hydrogen or oxygen in excess, together with a small quantity 

 of nitrogen, due to a little air which had leaked into the vessel. in the 

 course of the experiments, or which had been absorbed by the water. 

 The results of these analyses showed that there was always an excess 

 of oxygen in the test-tube in connexion with the positive electrode, 

 and an excess of hydrogen in the test-tube connected with the nega- 

 tive electrode, and, also, that the amounts of oxygen and hydrogen in 

 the respective tubes were very nearly chemically equivalent to the 

 amount of copper deposited from a solution of copper sulphate in a 

 voltameter placed in series with the discharge tube. 



The results of some of Perrot's experiments are shown in the 

 following table : — 



Duration of 

 experiment. 



Weight of Cu de- 

 posited in voltameter 

 and its equivalent 

 in c.c. of H. 



Excess of H in 

 tube next — 

 electrode. 



Excess of O in 

 tube next 4- 

 electrode. 



4 *0 hours 

 40 „ 

 3-0 „ 

 35 „ 



8-5 mgm.Cu; 3 00 c.c.H 

 6-0 „ 2-12 „ 

 55 „ 094 „ 

 60 „ 2-12 „ 



3 00 c.c. 

 2-10 „ 

 1-80 „ 

 205 „ 



1 *40 c.c. 

 0*95 „ 

 0-85 „ 

 0-90 „ 



Thus in Perrot's experiments the excess of hydrogen appears at the 

 negative electrode, the excess of oxygen at the positive, and these 

 excesses are very nearly chemically equivalent to the amount of Cu 

 deposited in a copper sulphate voltameter placed in series with the 

 discharge tube. Ludeking* confirmed the result that when sparks 

 pass through steam there is an excess of oxygen at the positive, and 

 of hydrogen at the negative, electrode. 



As these results bear very closely on the method by which the dis- 



* « Phil. Mag.' [5] vol. 33, 1892, p. 521. 



