| abstract |
A bis-9-anthrol or a bis-ortho-naphthol of the formula la or Ib or the keto tautomer of lan wherein X 1 and X 2 , each independently, represent an alkyl group containing from 1 to 4 carbon atoms or a fluorine or chlorine atom; m is 0, 1 or 2; n is 0, 1, 2, 3 or 4; and A is a certain divalent hydrocarbon radical. |