## Facts

- Inventors filed a patent application claiming a process for manufacturing nitrogen-containing crystalline metal silicates with a zeolite structure.
- Prior zeolite synthesis commonly required alkali metal (often sodium), then a separate ion-exchange step to remove alkali cations before catalytic use.
- The claimed process sought to avoid using alkali metal during synthesis, eliminating the need for ion exchange.
- Because trace alkali metal could be unavoidable, the claims used the limitation “essentially free of alkali metal.”
- An illustrative independent claim required adding specified metal compounds and a silicon dioxide source “essentially free of alkali metal” to an aqueous hexamethylenediamine solution, forming a gel, and heating to obtain crystalline metal silicate.
- The examiner rejected several claims for (1) anticipation under 35 U.S.C. § 102, (2) obviousness under 35 U.S.C. § 103, and (3) indefiniteness under 35 U.S.C. § 112 (second paragraph) based on “essentially free of alkali metal.”
- The Board of Appeals affirmed the examiner; the inventors appealed.

## Issues

1. Whether “essentially free of alkali metal” is indefinite under 35 U.S.C. § 112 (second paragraph) for failing to recite a numerical cutoff.
2. Whether the Board properly sustained anticipation and/or obviousness rejections under 35 U.S.C. §§ 102 and 103 for the appealed process claims in view of the prior art.

## Decision

- The Federal Circuit affirmed in part and reversed in part.
- The court reversed the § 112 indefiniteness rejection to the extent it rested on requiring a specific numerical cutoff for “essentially free of alkali metal.”
- The court affirmed some and reversed some of the Board’s §§ 102/103 determinations on a claim-by-claim basis.

## Legal Principles

- A claim is not indefinite merely because it uses a relative or functional term (e.g., “essentially free”) without a numeric boundary, if the meaning is reasonably clear to a person of ordinary skill in the art when read in light of the specification.
- The PTO cannot require an arbitrary numerical cutoff where the invention is not defined by a single number and where strict numerical precision is impractical in the relevant technology.
- Definiteness under § 112 is a distinct inquiry from patentability under §§ 102 and 103; once claim meaning is resolved, novelty and nonobviousness must still be evaluated against the prior art, claim by claim.

## Conclusion

The Federal Circuit held that “essentially free of alkali metal” was not indefinite simply for lacking a numerical threshold, rejecting a rigid numeric-cutoff demand, while separately evaluating novelty and obviousness and issuing a mixed affirmance and reversal on the prior-art rejections.


In re Marosi, 710 F.2d 799 (Fed. Cir. 1983)