Explanatory notes
… acid (H 2 SO 3 ) (which exists only in aqueous solution and corresponds to the sulphur dioxide of heading 28.11). … concentrated sulphite lye ( heading 38.04 ), and the industrial products known as “hydrosulphites” stabilised by … reducing agent in organic synthesis, in the manufacture of indigo, for bleaching wool or silk, as a vulcanising agent …