prov:value
| - owing formula (V): ##STR111## wherein each of R1 to R4 is H or an alkyl group, and Me is Cr, Cu or Fe; vi) an imide compound represented by the following formula (VI): ##STR112## wherein M is an alkali metal or ammonium ion; R1 is ##STR113## each of R2, R3, R4, R5, R6, R7, R8 and R9 is hydrogen, an alkyl group of 1-18 carbon atoms, a halogen, ##STR114## --NO2, or SO3 H, and they may be the same or
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