A claim’s “negative limitation” defines the invention in terms of what it is not, rather than with an affirmative description. In contrast, consider the following two cases:
- a claim with the limitation “said homo-polymer being free from the proteins, soaps, resins, and sugars present in natural Hevea rubber” in order to exclude the characteristics of a prior art product, was ruled to be definite because each recited limitation was definite. In re Wakefield, 422 F.2d 897; 164 USPQ 636, 638, 641 (CCPA 1970); and
- a negative limitation “incapable of forming a dye with said oxidized developing agent” was deemed definite because the boundaries of the patent protection sought were clear. In re Barr, 444 F.2d 588, 170 USPQ 330 (CCPA 1971).