It has now been shown that when chlorosulphonic acid is added to phenol in carbon disulphide at-15", phenylsulphuric acid and phenol+ sulphonic acid are formed. NO phenol- o-sulphonic acid was detected. Slow addition of the chlorosulphonic acid or long periods for reaction favoured the production of sulphonate. Under the conditions which gave most phenylsulphuric acid, the mixed barium salts obtained on extraction corresponded to 75% ...