text: Thiosulfate ions are stable only in neutral or alkaline solutions, but not in acidic solutions, due to disproportionation to sulfite ions and sulfur, the sulfite ions being dehydrated to sulfur dioxide:
  This reaction may be used to generate an aqueous suspension of sulfur and demonstrate the Rayleigh scattering of light in physics. If white light is shone from below, blue light is seen from sideways and orange light from above, due to the same mechanisms that color the sky at midday and dusk.
  Thiosulfate ions react with iodine to give tetrathionate ions:
  This reaction is key for iodometry.
  With bromine (X = Br) and chlorine (X = Cl), thiosulfate ions are oxidized to sulfate ions: