A frequently asked question is: "Can I patent a new use for an already existing product or tool?" Potentially yes, but care is in order. New uses for old things must be carefully phrased as "process" or "new use" claims.
For an example of the pitfalls, consider a discovery that could have made the discoverers immensely wealthy. In 1846, Drs. Morton and Jackson received U.S. Pat. No. 4848 covering the use of ether as a surgical anesthetic. Prior to that time, ether was well known as a compound, but its anesthetic properties were undiscovered. That patent was eventually held invalid, some 16 years later, because the inventors had claimed ether per se, rather than as part of a method of using it in anesthesia. It's an old patent, but available at
www.uspto.gov, and is an instruction in the subtle art of claiming. Morton and Jackson's language claiming the "means by which we were able to effect [anesthesia]" was held to claim the substance, ether, and not the process, by a New York federal court, even though the title of the invention is "Improvement in Surgical Operations;" language that certainly suggests a process or use.
Today, under 35 U.S.C. § 100(b), process claims are specifically defined to include "a new use of a known process, machine, manufacture, composition of matter, or material." However, caution is indicated. Inclusion in a claim of a simple intended use is insufficient to make out a method or process claim, for example, merely claiming "The use of…" has been rejected. The use must be recited as a true process, that is, one encompassing one or more specified steps. Also, finding a new use does not entitle one to any apparatus claim or substance claim on the material or machine - only the new process may be patented.
While we most often think of new processes to use old materials, can there be a new use or a new application of a previously patented process? The law is not entirely clear on this, but authorities believe that a new use, if claimed properly as a use, is patentable if it satisfies the nonobviousness standard of 35 U.S.C. §103. As is true in other obviousness determinations, a new use for a known process that would be obvious to one skilled in the art would not be patentable.