412 J. H. Reedy — -Anodic Potentials of Silver. 



the conditions which must be observed in the electrolytic 

 deposition of the halogens on silver, and not to perfect any 

 analytical procedure. Furthermore, the methods which have 

 been used in this work will hardly commend themselves to the 

 practical analyst. The apparatus is too elaborate, and the 

 manipulation is unsatisfactory in that it demands thorough 

 familiarity with this unusual kind of work, not to mention the 

 fact that the constant adjusting of the anode potential precludes 

 the carrying on of other experiments at the same time. How- 

 ever, it is hoped that this work will make clear what is possible 

 and what is impossible in the quantitative separation and 

 estimation of the halogens by means of a silver anode. 



Summary. 



The conclusions reached in this study of the determination 

 of the halogens by means of silver anodes may be briefly stated 

 as follows : 



(1) The anodic potential must be known at every stage of 

 the electrolysis, so that the maximum value of the potential for 

 that particular process may not be exceeded. 



(2) In no case may the anodic potential rise above '521 volts, 

 since silver dissolves at the potential. 



(3) The course of the electrolysis can not be properly con- 

 trolled by the regulation of the current, independent of the 

 anode potential. 



(4) Chlorine can not be satisfactorily estimated by electro- 

 lytic precipitation on silver, since the anodic potential required 

 for its complete deposition is approximately the same as that 

 at which silver dissolves. 



(5) Quantitative separation of the halogens is possible only 

 within certain definite limits of concentration. 



