458 Mr. J. Brown on the Role of 



(fig. 3 ) is from this experiment. The scale is too small to 

 show the part of the curve before decomposition of BrCl may 

 be assumed to begin. 



The secondary E.M.F. of this arrangement is, as might be 

 expected, still smaller than that for I CI. In the course of 

 the experiment none was detected with up to as much as *1 D. 

 applied E.M.F., and the highest secondary E.M.F. observed 

 was under -05 D. after an applied E.M.F. of 2 J Daniells. 



i 



Daniell. 



Fig. 3. — Electrolysis of Aqueous Solutions of Hydrogen-Iodine Chloride, 

 Bromine Chloride, and Hydrochloric Acid. Abscissae correspond to 

 electromotive force in parts of a Daniell ; ordinates to current as 

 measured by deflexions of a refiecting-galvanometer (the larger values 

 are about 5 per cent, too large on this instrument). 



The hydrochloric-acid curve is for a dilute solution, and is given 

 for comparison with the others. Regular electrolysis begins a little 

 under 1 D. The secondary E.M.F. was, of course, much greater 

 than in the other cases. For BrCl the sensitiveness of the galva- 

 nometer was less than for the others, giving a more horizontal line. 



21. When a zinc-platinum couple was immersed in the 

 aqueous solution gas was evolved from both metals, and the 

 liquid gradually became colourless without the appearance of 

 any bromine. 



In testing the electromotive force of combinations of this 

 electrolyte with various metals &c, the same apparatus and 



