Johann Friedrich Schweitzer, also known as John Frederick Helvetius was a Dutch physician and alchemical writer, of German extraction. He is known for his books Vitulus Aureus, published in 1667, Ichts aus Nichts, für alle Begierigen der Natur from 1655 and Miraculo transmutandi Metallica, Antwerp, 1667. He is notorious for the story that he actually carried out transmutation of lead into gold. He is also said to have been physician to the Prince of Orange of the time. His birthplace is given as Cöthen, Anhalt. He is said to have known Baruch Spinoza. He was an ancestor of the philosopher Claude-Adrien Helvétius.