$\begin{array}{1 1}\text{Dithionous acid},H_2S_2O_4\\\text{Dithionic acid},H_2S_2O_6\\\text{Polythionic acid},H_2S_{n+2}O_6\\\text{Pyrosulphuric acid},H_2S_2O_7\end{array} $
