## Facts

- Inventors Swinehart and Sfiligoj sought patent protection for crystalline compositions made from barium fluoride (BaF₂) and calcium fluoride (CaF₂) in approximately eutectic proportions.
- Eutectic BaF₂–CaF₂ mixtures were known; applicants asserted that melting and resolidifying these components using conventional crystal-growing methods produced a multi-phase crystalline body with improved properties.
- Applicants described the resulting crystalline material as not cleaving, resistant to thermal shock and impact, approaching maximum density, and capable of transmitting collimated light, particularly in the infrared range.
- The sole disputed claim (claim 24) defined the composition as “transparent to infra-red rays and resistant to thermal shock” and as a “solidified melt” of BaF₂ and CaF₂ in approximately eutectic proportions.
- The examiner rejected claim 24 under 35 U.S.C. § 112 for indefiniteness and overbreadth based on its functional language; the Board of Appeals affirmed that rejection, and applicants appealed.

## Issues

1. Whether a composition-of-matter claim that recites functional properties (“transparent to infra-red rays” and “resistant to thermal shock”) fails the definiteness requirement of 35 U.S.C. § 112 solely because it uses functional language.
2. Whether the claim’s functional limitations render the claim impermissibly broader than the enabling disclosure under 35 U.S.C. § 112.

## Decision

- The Court of Customs and Patent Appeals reversed the Board’s affirmance of the § 112 rejection of claim 24.
- The court held that functional language in a claim is not improper per se under § 112, including in chemical and materials claims.
- In context, the court found the recited properties sufficiently definite because they were technically meaningful and objectively ascertainable by those skilled in the art.
- The court rejected the view that breadth alone establishes indefiniteness or lack of support where the specification enables skilled artisans to make and use the claimed compositions within the claim’s scope.

## Legal Principles

- Functional limitations are permissible in patent claims when, read in light of the specification and knowledge in the art, they provide a sufficiently definite boundary for the claim.
- A claim is not indefinite merely because it is broad; § 112 requires that the specification enable those skilled in the art to make and use the invention across the claim’s scope without undue experimentation.
- Technical property terms may satisfy § 112 definiteness when their meaning and measurement are sufficiently clear in the relevant field, even if the property is expressed functionally.

## Conclusion

The CCPA set aside the § 112 rejection and held that a composition claim may define the invention by functional, property-based limitations when those properties are objectively determinable and the disclosure enables skilled artisans to practice the invention across the claimed range.


Application of Swinehart (In re Swinehart), 439 F.2d 210 (C.C.P.A. 1971)