prov:value
| - All the previous criteria involved in the subject invention are satisfied by utilizing a dye having a structure based on ##STR2## where Y is SO3 G (G being an alkali metal cation) or H, R1 and R2 are individually hydrogen, methyl or ethyl, R3 is a group such as H, a lower alkyl (preferably less than 5 carbon atoms), p-tolyl, or xylyl, where Z- is Cl-, Br-, I-, NO3 -, or p-toluenesulfonate.
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