Arylsulphaminoarylsulphonic acids and arylsulphoxyarylsulphonic acids precipitate gelatine but are devoid of tannoid character. The latter is acquired by compounds belonging to this class containing two or more sulphamino groups, or when they, in addition to one sulphamino group, contain a sulphoxy group and another sulphonic group. According to Ger. Pat., 297,187 (Society oc Chemical Industry, Basle), such compounds are obtained when, for instance, sodium sulphanilide in alkaline solution acts upon nitrotoluenesulphochloride, and the resulting nitrotoluenesulphamino compound is subsequently reduced with acetic acid and iron. The resulting aminotoluenesulphaminobenzenesulphonic acid is finally treated with p-toluenesulphonic chloride till the latter disappears. A compound of the composition -----NH-----SO_2----- ^ ^ ^ | | | | | | | | | |---NH---| | V V V SO_2Na CH_2 is thereby obtained, which, when acidified, is readily capable of being used for tanning purposes. The intermediary product of the aminotoluenesulphaminobenzenesulphonic acid obtained by this process may again be employed for the purpose of reacting with one-half molecule soda and 1 molecule nitrotoluenesulphonic chloride. The following compound is obtained-- ---NH---SO_2--- ---NH---SO_2--- ^ ^ ^ CH_3 ^ | | | | | | | | | | | | | | | | v v ---NH---SO_2--- v v SO_3Na CH_3 CH_3 If _p_-toluenesulphaminobenzenesulphonic chloride is condensed with sodium sulphanilide, a compound, ---SO_2---NH--- NaSO_3 ^ ^ ^ | | | | | | | | | | | | v v ---SO_2---NH--- v SO_3Na is obtained which, when acidified, exhibits tannoid properties. On condensing sodium phenolsulphonate with nitrotoluenesulphonic chloride, reducing the condensation product and condensing the latter with _p_-toluenesulphonic chloride, a compound similar to the above is obtained-- ---O---SO_2--- ^ ^ ^ CH_3 | | | | | | | | | | | | v v ---NH---SO_2--- v NaSO_3 CH_3 Again, a similar product is obtained when _p_-toluenesulphaminobenzenesulphonic chloride or its homologues or isomers are condensed with sodium-_o_-cresylsulphonate-- ---SO_2---NH--- SO_3Na ^ ^ ^ | | | | | | | | | | CH_3| | v v ---SO_2---O--- v CH_3