. "Both the isocyclic and the heterocyclic aromatic radicals may contain the customary non-watersolubilising substituents such as: (1) Halogen atoms, e.g. chlorine, bromine or fluorine atoms. (2) Branched or unbranched alkyl groups containing preferably 1 to 18, especially 1 to 12, more particularly 1 to 8 and, most preferably, 1 to 4 carbon atoms." . . .