Interhalogen compounds are formed from two different halogens. These compounds resemble the halogens themselves in both their physical and chemical properties. Principal differences show up in their electronegativities. This is clearly shown by the polar compound IC1, which has a boiling point almost 40° C above that of bromine, although both have the same molecular weights. Interhalogens have bond energies that are lower than halogens and therefore in most cases they are more reactive. These properties impart special germicidal characteristics to these compounds. The principal germicidal compound of this group is bromine chloride. At equilibrium, BrCl is a fuming dark red liquid below 5° C. It exists as a solid only at relatively low temperatures. Liquid BrCl can be vaporized and metered as a vapor in equipment similar to that used for chlorine.
BrCl is prepared by the addition of equivalent amounts of chlorine to bromine until the solution has increased in weight by 44.3 percent: The reaction is as follows:
BrCl can be prepared by the reaction in the gas phase or in aqueous hydrochloric acid solution. In the laboratory, BrCl is prepared by oxidizing bromide salt in a solution containing hydrochloric acid.
BrCl exists in equilibrium with bromine and chlorine in both gas and liquid phases. Table 5 lists various physical properties of BrCl. Due to the polarity of BrCl, it shows greater solubility than bromine in polar solvents. In water, it has a solubility of 8.5 gms per 100 gms of water at 20o C (that is, 2.5 times the solubility of bromine; 11 times that of chlorine). Bromine chloride's solubility in water is increased greatly by adding chloride ions to form the complex chlorobromate ion, BrCl,.
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