Johann Friedrich Schweitzer (1625–1709) was a Dutch physician and alchemical writer, of German extraction. He is known for his book Vitulus Aureus (The Golden Calf), published in 1667. Another book is Ichts aus Nichts, für alle Begierigen der Natur from 1655.

He is notorious for the story that he actually carried out transmutation

Alchemy

Alchemy is an influential philosophical tradition whose early practitioners’ claims to profound powers were known from antiquity. The defining objectives of alchemy are varied; these include the creation of the fabled philosopher's stone possessing powers including the capability of turning base...

 of lead into gold. He is also said to have been physician to the Prince of Orange

Prince of Orange

Prince of Orange is a title of nobility, originally associated with the Principality of Orange, in what is now southern France. In French it is la Principauté d'Orange....

 of the time. His birthplace is given as Köthen, Anhalt

Anhalt

Anhalt was a sovereign county in Germany, located between the Harz Mountains and the river Elbe in Middle Germany. It now forms part of the state of Saxony-Anhalt.- Dukes of Anhalt :...

. He is said to have known Baruch Spinoza

Baruch Spinoza

Baruch de Spinoza and later Benedict de Spinoza was a Dutch Jewish philosopher. Revealing considerable scientific aptitude, the breadth and importance of Spinoza's work was not fully realized until years after his death...

.

He was an ancestor of the philosopher Claude-Adrien Helvétius.