550 Gooch and Read — Determination of Chlorine. 



were contained in the solution. In one experiment (6) the 

 solution, neutral to litmus, became spontaneously opalescent 

 after standing forty-eight hours, as might very well be the 

 case if the solution contained a trace of silver hypochlorite at 

 the end of the electrolysis. These phenomena show that in 

 the electrolytic analysis of hydrochloric acid with the silver- 

 plated anode the process does not consist simply of the libera- 

 tion of hydrogen at the cathode and the fixation of chlorine at 

 the anode, but that these effects may be supplemented to a 

 greater or less extent, according to the conditions, by the 

 fixation of oxygen as well as chlorine, the production of 

 oxygen compounds of chlorine, and the dissolving of silver 

 from the anode with its more or less complete transfer to the 

 cathode. Of silver ii) solution a trace was sometimes found by 

 hydrogen sulphide but not enough to give a distinct test with 

 hydrochloric acid, though in experiment (6) a trace of silver 

 chloride was apparently thrown out spontaneously on standing. 



In experiments (4) and (6) tests of the liquid with silver 

 nitrate were omitted and the residues left on evaporation and 

 heating were found to weigh 0*0029 and 0'0035 grm. respec- 

 tively. Each residue was soluble in water and, after ignition, 

 gave a test for chlorine with silver nitrate. Each contained 

 no appreciable amount of silver, but did contain potassium ; 

 and, inasmuch as the acid taken left upon evaporation only an 

 inconsiderable residue, the inference seemed plain that at least 

 the greater part of the solid material must have been derived 

 from salt included in the plating of the anode. Before pro- 

 ceeding further, therefore, this point was decided by carefully 

 washing as usual a freshly plated anode, suspending it for some 

 minutes in a beaker of water kept boiling, and then testing 

 the water with silver nitrate, the production of cloudiness 

 being taken as an indication of the presence of a soluble 

 cyanide. 



In Series B of the table are the results obtained in-two 

 experiments with the silver-plated anode carefully boiled out 

 and gently ignited previous to its use in the electrolytic 

 process. In experiment (8) mercury in a glass beaker and con- 

 nected with the battery by a platinum wire sealed into glass to 

 prevent contact with the liquid served as the cathode. In 

 each of these experiments the neutrality of the residual liquids 

 proved the absence of hydrochloric acid. In (7) a trace of 

 silver was found upon the cathode, and the liquid became 

 faintly cloudy toward the end of the electrolysis and left upon 

 evaporation a residue of 0*0024, of which 0*0011 was insoluble in 

 water and apparently silver chloride. In (8) a small portion 

 of the liquid gave a precipitate with silver nitrate and the 

 remainder left a residue of 0*0020 grm. These results confirm 



