U.S. Patent Application #209,634 – Tobacco Smoke Filtering, 1938-1939

To request archival materials you must have a research appointment already scheduled. To make a research appointment, please fill out our appointment form and a librarian will contact you to confirm.

To ask our library staff a question, please email us at research@sciencehistory.org or submit a question via our reference question form. To request that something be digitized, contact us at reproductions@sciencehistory.org or visit https://www.sciencehistory.org/rights-and-reproductions. For more information about the library and our collections, please visit https://www.sciencehistory.org/othmer-library.