Note 79 — Chapter XI · THE HALOGENS: CHLORINE, BROMINE, IODINE, AND FLUORINE

Hypoiodous acid, HIO, is not known, but organic compounds, RIO, of this type are known. To illustrate the peculiarities of their properties we will mention one of these compounds, namely, iodosobenzol, C6H5IO. This substance was obtained by Willgerodt (1892), and also by V. Meyer, Wachter, and Askenasy, by the action of caustic alkalis upon phenoldiiodochloride, C6H5ICl2 (according to the equation, C6H5ICl2 + 2MOH = C6H5IO + 2MCl + H2O). Iodosobenzol is an amorphous yellow substance, whose melting point could not be determined because it explodes at 210°, decomposing with the evolution of iodine vapour. This substance dissolves in hot water and alcohol, but is not soluble in the majority of other neutral organic solvents. If acids do not oxidise C6H5IO, they give saline compounds in which iodosobenzol appears as a basic oxide of a diatomic metal, C6H5I. Thus, for instance, when an acetic acid solution of iodosobenzol is treated with a solution of nitric acid, it gives large monoclinic crystals of a nitric acid salt having the composition C6H5I(NO3)2 (like Ca(NO3)2). In appearing as the analogue of basic oxides, iodosobenzol displaces iodine from potassium iodide (in a solution acidulated with acetic or hydrochloric acid)—i.e. it acts with its oxygen like HClO. The action of peroxide of hydrogen, chromic acid, and other similar oxidising agents gives iodoxybenzol, C6H5IO2, which is a neutral substance—i.e. incapable of giving salts with acids (compare Chapter XIII. Note 43).