## Facts

- Tannage Patent Company, as assignee of inventor Augustus Schultz, sued William Zahn in equity for infringing two process patents for “tawing hides and skins.”
- The suit involved U.S. Patent Nos. 291,784 and 291,785 (both issued Jan. 8, 1884), each claiming a two-step chemical process.
- Both patents described first treating hides/skins in a bath prepared from a metallic salt, exemplified by bichromate of potash.
- The second step in each patent applied sulphurous acid action to the hide/skin after the first bath, either:
  - indirectly by using hyposulphite (thiosulfate) in the presence of acid to generate sulphurous acid, or
  - directly by using a bath containing or capable of evolving sulphurous acid, exemplified by sulphite of soda.
- The court viewed the two patents as materially the same in operative means, differing mainly in descriptive wording.
- Zahn denied infringement and challenged validity, arguing the specifications did not sufficiently teach the processes and the claims were drawn too broadly beyond what was disclosed.
- Zahn’s accused method used a similar two-bath chrome tawing approach: a bichromate/metallic-salt bath followed by a sulphite or sulphurous-acid–releasing treatment.

## Issues

1. Whether the patent specifications sufficiently described and enabled the claimed tawing processes for use by a person skilled in the art.
2. Whether the claims were impermissibly broad or indefinite relative to the disclosed processes, rendering the patents invalid.
3. Whether Zahn’s process fell within the scope of the claims, if valid.

## Decision

- The court sustained the validity of both patents, rejecting challenges based on insufficient disclosure and excessive breadth.
- The court concluded the specifications provided an adequate practical teaching of the processes to skilled tanners.
- The court held Zahn infringed because his process employed the same two-step chrome treatment followed by sulphurous-acid action, within the claims’ scope.
- Relief was granted to Tannage Patent Company (consistent with an equity decree in patent infringement matters).

## Legal Principles

- A process patent’s specification is sufficient if it enables a person skilled in the relevant art to practice the invention without undue experimentation; it need not enumerate every operating detail or variant.
- Claims may use reasonably general, functional chemical language when supported by disclosure of the operative process and representative materials that teach how to carry it out.
- Use of substantially the same sequence of steps and chemically equivalent treatments can fall within process claims that cover a bath “such as” specified examples and a second bath containing or generating the stated active agent.

## Conclusion

The trial court upheld Schultz’s tawing process patents as adequately disclosed and appropriately claimed, and found infringement where the accused method applied the same two-bath chrome treatment followed by sulphurous-acid action to taw hides and skins.


Tannage Patent Co. v. Zahn, 66 F. 986 (C.C.D.N.J. 1895)