The nature of the solutions of some inorganic halides in disulphuric acid

Abstract

Tetrachlorides of selenium and tellurium form the pyramidal cation MCl₃⁺ when dissolved in disulphuric acid. Tellurium tetrabromide disproportionates and phosphorus pentachloride forms PCl₄⁺ ions, whereas phosphorus pentabromide forms phosphoryl bromide and iodine trichloride forms ICl₂⁺. However, mono- and di-chlorides of sulphur and selenium disproportionate to give elements and tetrachloride. Trihalides of phosphorus are oxidised to phosphoryl halides which become protonated but trihalides of arsenic and antimony are solvolysed to form hydrogen sulphate.