(John), a celebrated Saxon chemist, born in the duchy of Sleswick, in 1630. He became chemist to the elector of Saxony, the elector of Brandenburg, and Charles II. king of Sweden, who gave him the title of counsellor in metals, and letters of nobility, with the surname of Louwenstein. He employed 50 years in chemistry; in which, by the help of the furnace of a glas-boute, which he had under his care, he made several excellent discoveries, particularly of the phosphorus of urine. He died in Sweden, in 1702; and left several works, some in German, and others in Latin; among which, that intitled Observations Chemicae, and the "Art of making Glais," printed at Paris in 1752, are the most esteemed.