436 Gooch and Gates — -Decomposition of Hydrochloric Acid. 



and certain derived inferences as to the part played by water 

 in carrying the current of electricity and as to the speed of 

 transportation of the chlorine and hydrogen ions. In the 

 experiments first recorded,* an electrode of platinum wire 

 G*5 mm in diameter and 6 CIU in length was used, and in these 

 experiments it was found that the volumes of oxygen delivered 

 free at the anode, by currents ranging from 0'120 amp to 

 0*134 amp , continued through intervals of about an hour, bore 

 to the volumes of hydrogen simultaneously set free at the 

 cathode a relation changing with the concentration of the solu- 

 tion. Taking the volume of hydrogen evolved as unity, the 

 ratios of the volumes of oxygen and hydrogen, expressed 

 fractionally for varying concentrations, are as follows : 



Concentration 



per thousand: 14*o 8*7 5*8 2*9 1*45 (?) 0*72 



Ratio of oxygen 

 to hydrogen: 034 0*068 0*082 0*120 0*166 0*212 



Similar results were obtained in another experiment in 

 which a silver anode (of unrecorded dimensions) was employed 

 to fix the chlorine ; but the evolution of oxygen was found to 

 be relatively greater, the ratio for a concentration of 0*72 

 parts of hydrochloric acid to 1000 parts of solution being 0*253 

 as compared with 0*212 obtained under similar conditions with 

 the platinum anode. From the fact that the evolution of 

 oxygen did not cease, but was rather actually increased under 

 such conditions, Doumer drew the conclusion that the libera- 

 tion of oxygen in the electrolysis of hydrochloric acid cannot 

 be attributed to the secondary action of chlorine on the water 

 of the solution, and that there is direct electrolytic decomposi- 

 tion of water as well as of acid. 



In a subsequent articlef the account is given of a similar 

 experiment, with the silver anode, in which readings of the 

 gas delivered were taken through twenty consecutive periods 

 of fiYe minutes each. It is stated that when a silver anode is 

 employed for the electrolysis of hydrochloric acid, brown 

 silver oxide is formed until the deposit of oxide and chloride 

 upon the anode reaches a thickness which it does not seem 

 able to exceed, and that thereafter the liberation of oxygen 

 becomes constant, while the chlorine produced in the electrol- 

 ysis remains fixed on the anode as silver chloride. The liquid 

 contains no trace of free chlorine or of oxychlorides when 

 weak currents are employed. During the first twenty minutes 

 of preliminary electrolysis, in the experiment recorded, no 

 note was taken of the volumes of gas liberated. For the first 



*Compt. Rend., cxlvi, 329-331. fCompt. Rend., cxlvi, 687-690. 



