group 17 elements : Uses 

    The nuclear fuel industry uses large quantities of F₂ in the production of UF₆ for fuel enrichment processes and this is now the major use of F₂. Industrially,  the most important F-containing compounds are HF, BF₃,F₂ (as a flux in metallurgy), synthetic cryolite and chlorofluorocarbons. Figure 1.1a summarizes the major uses of chlorine. Chlorinated organic compounds, including 1,2-dichloroethene and vinyl chloride for the polymer industry, are hugely important. Dichlorine was widely used as a bleach in the paper and pulp industry, but environmental legislations have resulted in changes (Figure 1.1b). Chlorine dioxide, ClO₂ (an ‘elemental chlorine-free’ bleaching agent), is prepared from NaClO₃ and is favoured over Cl₂ because it does not produce toxic effluents.

      The manufacture of bromine- and iodine-containing organic compounds is a primary application of these halogens. Other uses include those of iodide salts (e.g. KI) and silver bromide in the photographic industry, bromine-based organic compounds as flame retardants and solutions of I₂ in aqueous KI as disinfectants for wounds. Iodine is essential for life and a deficiency results in a swollen thyroid gland; ‘iodized salt’ (NaCl with added I^-) provides us with iodine supplement.

Fig. 1.1 (a) Industrial uses of Cl₂ in Western Europe in 1994 [data: Chemistry & Industry (1995) p. 832]. (b) The trends in uses of bleaching agents in the pulp industry between 1990 and 2001; ClO₂ has replaced Cl₂. Both elemental chlorine-free and totally chlorine-free agents comply with environmental legislations [data: Alliance for Environmental Technology, 2001 International Survey].