1886.] of Detecting Bromides. 377 



Id this way it is quite easy to detect one part of bromine in 

 C000 parts of water. Probably a much smaller quantity would be 

 apparent. 



If the decomposition is due to the formation of hypobromite, it 

 is evident that bromide will be again produced by its action on the 

 carbamate, and provided that there is always excess of hypochlorite 

 present the action should be continuous. 



The total amount of decomposition does, in fact, appear to be 

 independent of the mass of bromide present, at any rate within 

 very wide limits — i.e. any appreciable quantity of bromide would 

 be able to cause the decomposition of an almost unlimited amount 

 of carbamate in presence of hypochlorite. 



Thus "3854 grams of potassium bromide readily caused the 

 evolution of 340 c.c. of nitrogen from the above mixture, and the 

 resulting solution was still strongly " active " — i.e. at once caused 

 an evolution of nitrogen from fresh portions of the mixture. This 

 quantity of bromide in the form of hypobromite alone, could only 

 have caused the evolution of 24"07 c.c. 



The initial rate of decomposition however is evidently a func- 

 tion of the mass of bromide present (at any rate within certain 

 limits). A rough preliminary experiment, in this direction, was 

 made as follows: 



A mixture was prepared of sodium carbamate with excess of 

 sodium hypochlorite and hydroxide. Three equal volumes of this 

 solution were placed in separate vessels provided with stoppers 

 and delivery tubes*. 



5 c.c. (A), 10 c.c. (B), and 20 c.c. (C) of an arbitrary solution of 

 potassium bromide were introduced into small tubes, the first and 



Masses of Bromide. 

 C :: 1 : 2 : i) 



second being diluted with 15 c.c. and 10 c.c. of water respectively so 



as to make the total volumes equal. These small tubes were then 



* Chem. Soc. Journ., Ju]y, 1878, 



