Appeal No. 95-4826
Application 08/141,752
that appealed claim 14 (and claim 16) require that the xanthene
ring be methyl substituted. We agree with the examiner that the
use of such homologues would have been prima facie obvious to one
of ordinary skill in the art since compounds with such similar
structures would have been expected to have similar properties
and utilities. Ex parte Fauque, 121 USPQ 425 (Bd. App. 1954).
Friedrich discloses in Example 1 a water soluble dyestuff of
formula VIII, which differs from the dyestuffs in appealed claims
14 and 16 in not possessing a second sulfonic acid substituent on
the benzene ring and not possessing the methyl substituents on
the xanthene ring. However, Friedrich teaches that methyl
substituents on the xanthene ring "are understood" to be within
the disclosed invention. Further, the methyl substituted
dyestuffs are such structurally similar homologues that they
would have been prima facie obvious to one of ordinary skill in
the art. We agree with the examiner that it would have been
prima facie obvious to add an additional sulfonic acid
substituent to the benzene ring of Friedrich's dyestuff VIII.
Sulfonic acid substituents are routinely used to improve the
solubility of water soluble dyes, and we note, for example, that
Austin discloses that his xanthene dyes preferably contain "more
3
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