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Desalination of Sea Water

As Secretary of State, Thomas Jefferson accompanied President Washington on his trip to Newport and Providence, Rhode Island in August 1790, and Jefferson was probably present when Jacob Isaacks presented the President with a bottle of desalinated seawater on their stop in Newport. Evidently, Isaacks had a mixture that helped desalinate the water.[1]

In 1791, Isaacks' petition from Congress was sent to Jefferson as Secretary of State, an office which held a seat on the board of the patent office. To test this process, Jefferson brought in some fellow members of the American Philosophical Society - Caspar Wistar, James Hutchinson, and David Rittenhouse - to witness Isaacks' demonstration and to conduct experiments on their own.

On March 25, 1791, Jefferson outlined the testing and results in "Affidavit of the Secretary of State on the Result of the Experiments.[2] The experiments were conducted over a four-day period (20 hours worth of work in all) both in his offices at the State Department and at the College of Philadelphia, where both Wistar and Hutchinson were professors. Jefferson concluded, "that as far as these experiments justify a conclusion, Mr. Isaack's mixture does not facilitate the separation of sea-water from it's salt.[3]

Jefferson did not send his official report to Congress until November and it was expanded to include a history of desalination along with a synopsis of the experiments conducted. His conclusion was the same as in the affidavit.[4]

In his report, Jefferson states, " should be made the occasion of disseminating it's knowledge generally and effectually among the sea-faring citizens of the U.S."[5] He recommended that desalination methods be printed on the back of the permit issued for every vessel sailing from U.S. ports. Congress did pass a resolution in May 1792 that new clearance forms be created with one side containing descriptions of desalination methods.


  1. This article is based on Gaye Wilson, Monticello Research Report, January 2001.
  2. See PTJ,19:617-618.
  3. Ibid, 618.
  4. Ibid, 22:321.
  5. Ibid.

Further Sources


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