 Trace-scale heating of radon with xenon, fluorine, bromine pentafluoride, and either sodium fluoride or nickel fluoride was claimed to produce a higher fluoride as well which hydrolysed to form .While it has been suggested that these claims were really due to radon precipitating out as the solid complex [RnF][NiF6]2−, the fact that radon coprecipitates from aqueous solution with has been taken as confirmation that was formed, which has been supported by further studies of the hydrolysed solution.That [RnO3F]− did not form in other experiments may have been due to the high concentration of fluoride used.