Reversible Sulfonation of Aniline? If I have aniline in acid and fuming $\ce{SO3}$, will it reversibly sufonate? I am worried that the nitrogen will be protonated and reduce the nucleophilicity of benzene ring to the point where sulfonation just isn't possible and instead you just get a salt? Or is it possible that you only get mono-sulfonation?

Here is my reaction scheme:
It sulfonates on N first and then rearranges on heating to give sulfonation in the 4 position. JACS 68 (1946) 969