1893.] 



The Electrolysis of Steam. 



for believing that when a spark passes through a gas it produces 

 a supply of a modification of the gas, whose conductivity is enor- 

 mously greater than that of the original gas. I have shown (' Phil. 

 Mag.,' November, 1891) that the conductivity of this modified gas is 

 comparable with that of strong solutions of electrolytes. When the 

 discharge stops this modified gas goes back to its original condition. 

 If now the discharges through the gas follow each other so rapidly 

 that the modified gas produced by one discharge has not time to return 

 to its original condition before the next discharge passes, the succes- 

 sive discharges will pass through this modified gas. If, on the 

 other hand, the gas has time to revert to its original condition 

 before the next discharge passes, then the discharges pass through 

 the unmodified gas ; we regard this as being accomplished by means 

 of successive decompositions and recombinations of its molecules, 

 analogous to those which, on Grotthus' theory of electrolysis, occur 

 when a current passes through an electrolyte. 



We regard the arc discharge as corresponding to the first of the 

 preceding cases where the discharge passes through the modified gas, 

 the spark discharge corresponding to the second when the discharge 

 goes through the gas in its unmodified condition. 



From this point of view, the explanation of the results of the ex- 

 periments on the electrolysis of steam are very simple. The modified 

 gas produced by the passage of the discharge through the steam con- 

 sists of a mixture of hydrogen and oxygen, these gases being in the 

 same condition as when the arc discharge passes through hydrogen 

 and oxygen respectively, when, as we have seen, the hydrogen behaves 

 as if it had a negative charge, the oxygen as if it had a positive one. 

 Thus, in the case of the arc in steam, the oxygen, since it behaves as 

 if it had a positive charge, will go to the negative, while the hydro- 

 gen, behaving as if it had a negative charge, will go to the positive 

 electrode. We saw that this separation of the hydrogen and oxygen 

 took place. 



The correspondence between the quantities of hydrogen and oxygen 

 from the electrolysis of the steam and those liberated by the electro- 

 lysis of water shows that the charges on the atoms of the modified 

 oxygen and hydrogen are the same in amount, but opposite in sign to- 

 those we ascribe to them in ordinary electrolytes. 



In the case of the long sparks where the discharge goes through 

 the steam, since the molecule of steam consists of two positively 

 charged hydrogen atoms and one negatively charged oxygen one, when 

 the molecule splits up in the electric field the hydrogen will go towards 

 the negative, the oxygen towards the positive, electrode, as in ordinary 

 electrolysis. We saw (p. 103) that for long sparks through steam 

 the hydrogen appeared at the negative, the oxygen at the positive, 

 electrode. 



