American inventor of the colonial and revolutionary period; died 1798. He was resident in Newport in 1755 ("Publications Am. Jew. Hist. Soc." v. 199), and on Feb. 17, 1758, he carried a law-case before the king in council, securing a favorable judgment. His family is mentioned as including five souls in 1760 (ib. x. 8); in 1762 he is mentioned by Ezra Stiles as being the owner of a brig (ib. viii. 124). In 1790 he presented to Washington, on the occasion of the president's visit to Newport, a bottle of water "extracted from ocean water, so free from saline matter as to answer for all the common and culinary purposes of fountain or river water"; and "the president was pleased to express himself highly satisfied therewith" (Max J. Kohler, in ib. vi. 78). A detailed account of his attempts to extract fresh from salt water is furnished by H. Friedenwald (ib. ii. 111 et seq.); it shows that Isaacs presented a petition to the House of Representatives in 1791, offering to convey the rights in his discovery to the United States for proper remuneration. The matter was referred to Thomas Jefferson, who communicated on the subject with well-known men of science. Jefferson's memorandum was favorable to Isaacs, but Congress took no action in the matter.