The hydronium ion also forms stable compounds with the carborane superacid . X-ray crystallography shows a symmetry for the hydronium ion with each proton interacting with a bromine atom each from three carborane anions 320 pm apart on average. The salt is also soluble in benzene. In crystals grown from a benzene solution the solvent co-crystallizes and a cation is completely separated from the anion. In the cation three benzene molecules surround hydronium forming pi-cation interactions with the hydrogen atoms. The closest (non-bonding) approach of the anion at chlorine to the cation at oxygen is 348 pm.