526 Mr Wilks, The Absorption of Bromine hy Lime. 



The Absorption of Bromine by Lime. By W. A. R. Wilks, B.A., 

 Gonville and Caius College. (Communicated by Dr Fenton.) 



[Head 23 May 1910.] 



The action of bromine on slaked lime was first investigated by 

 Berzelius. The product obtained — often called " bromine-bleaching 

 powder" — appears to have been very little studied since. Owing 

 to the fact that many adsorption compounds, as in the well- 

 known instance of iodide of starch, have peculiar colours it was 

 suspected that this might be a similar case. The product has a 

 reddish brown colour, and as this appears to be anomalous, at 

 Dr Fenton's suggestion the author undertook an investigation on 

 the subject. 



A series of experiments was carried out in the following way. 

 A gram of pure freshly prepared slaked lime (dried in a vacuum 

 desiccator) was weighed into a stoppered glass bottle and 100 c.c. 

 of a carbon tetrachloride solution of bromine (of known strength) 

 added. Solutions of different strengths were added to the same 

 quantity of lime in other bottles, the volume of solution being 

 always 100 c.c. After equilibrium was attained the strengths of 

 the solutions were determined by means of potassium iodide. The 

 concentration of bromine in the lime was then calculated. The 

 following are some of the results obtained. 



The thiosulphate contained "02108 grm. of NaaS^Og per c.c. 

 Temperature of experiment 15° C. In this experiment the con- 

 centration of- bromine in the lime was constant while the concen- 

 tration in the solution varied. The most probable interpretation 

 of this result is that a chemical compound is formed, probably 

 analogous to bleaching powder. The ratio Ca (OH)^ : Br = 4-42 : 1. 



Much weaker solutions of bromine were used in the next 

 experiments which were carried out in the same way as before. 



