OF ABTS AND SCIENCES. 91 



VII. 



AN INDIRECT DETERMINATION OF CHLORINE AND 

 BROMINE BY ELECTROLYSIS. 



By Leoxard p. Kinnicutt. 



Presented November 9th, 1881. 



In the indirect determination of chlorine and bromine the method 

 most commonly employed is to precipitate both halogens with argentic 

 nitrate, and then either to reduce the weighed argentic chloride and 

 bromide to metallic silver by heating in an atmosphere of hydrogen, 

 or to change the bromide into chloride by heating in a stream of 

 chlorine gas. 



The determination by either method is difficult, requires the closest 

 attention, and is liable to give erroneous results ; both on account of 

 the slight loss that may occur in transferring the weighed chloride 

 and bromide from the crucible to the glass tube, and also from slight 

 volatilization during the heating. I have found that even in reducing 

 the mixed haloids to metallic silver in a slow current of hydrogen, 

 small particles of silver are almost always carried by the gas along 

 the tube. Led by these facts, I attempted during the past winter to 

 find a new method which would, if possible, from its accuracy and 

 simplicity, tend to bring the indirect determination of chlorine and 

 bromine when they occur in organic compounds more into vogue than 

 is at present the case. In this attempt I believe I have been success- 

 ful, and the method I have devised is based on the principle that 

 melted argentic chloride and bromide are easily reduced to metallic 

 silver by the galvanic current. 



The details of the process are as follows : — 



After the mixture of the two halogen compounds of silver has been 

 heated in a porcelain crucible so that they just fuse together, the cru- 

 cible is cooled and weighed, a piece of platinum foil connected with a 

 platinum wire is placed in the crucible so that it rests on the melted 

 silver salts, and dilute sulphuric acid (1 pt. cone, to 3 pts. water by 



