Goocli and Read — Determination of Chlorine. 545 



form of silver dioxide), and that account must be taken of 

 silver dissolved from the anode. These are points which 

 appear to have escaped the consideration of subsequent 

 workers. 



Speketer,* in the electrolytic separation of chlorine, bromine, 

 and iodine under graded, potential of current, dried the silver 

 anode at 120°. 



Smithf deposited the chlorine of the chlorides of sodium, 

 barium and strontium upon an anode of silver gauze, the 

 cathode being either platinum or mercury used as described 

 by Mjers.J Upon passing the current the silver began to 

 darken almost immediately from the lower edge upward, and 

 when no further progress in the darkening was observed, it 

 was assumed that the operation was at an end. The gauze was 

 rinsed with water, alcohol, and ether, and was weighed after 

 drying a short time. The alkali in solution was determined 

 by titration with standard acid. 



Withrow§ determined similarly the iodine of potassium 

 iodide and the chlorine of potassium chloride with the use of 

 a spiral platinum cathode rotating at 300 to 500 revolutions 

 per minute and a silver dish used as the anode. The deposit 

 was dried in an air bath for weighing. 



Hildebrand|| made use of an anode of silver gauze, either 

 stationary or rotary, with either a simple mercury cathode or 

 a mercury cathode arranged so that an amalgam of the liberated 

 metal might be formed in an inner compartment and decomposed 

 largely in an outer annular compartment. The gradual fall- 

 ing of the current to a minimum (0*005 to 0*02 amperes), 

 determined by the formation of a small amount of alkali in 

 the solution, indicated the advance of the process to completion. 

 Hildebrand noted that after all the salt had been decomposed 

 the weight of the silver anode might be indefinitely increased 

 by the formation of silver oxide upon it, and, to avoid con- 

 tinuing the electrolysis after complete decomposition of the 

 salt, adopted the plan of diluting the liquid when the current 

 had apparently reached its minimum and stopping the current 

 as soon as the fresh anode surface thus brought into action 

 showed the formation of brown silver oxide. The gauze was 

 removed, immersed in alcohol and then in ether, dried,!" and 

 weighed. To secure the double advantage of making the 

 anode deposits perfectly adherent and stirring the amalgam to 

 secure complete decomposition in the outer compartment, 

 rotation of the anode was tried, and the statement is made 



*Zeitschr. f. Electroehern., 4. 



+ Jour. Amer. Chem. Soc, xxv, 890 (1903). {Ibid., xxvi, 1124. 

 § Ibid., xxviii, 1350 (1906). || Ibid., xxix, 447 (1907). 



*7 Smith : Electro Analysis (1907), p. 305. " Dry the gauze over a steam 

 radiator." 



