The decahydrate of sodium sulfate is known as Glauber's salt after the Dutch–German chemist and apothecary Johann Rudolf Glauber (1604–1670), who discovered it in Austrian spring water in 1625. He named it sal mirabilis (miraculous salt), because of its medicinal properties: the crystals were used as a general-purpose laxative, until more sophisticated alternatives came about in the 1900s.[4][5] However, J. Kunckel later alleged that it was known as a secret medicine in Saxony already in the mid-16th century.[6] In the 18th century, Glauber's salt began to be used as a raw material for the industrial production of soda ash (sodium carbonate), by reaction with potash (potassium carbonate). Demand for soda ash increased, and the supply of sodium sulfate had to increase in line. Therefore, in the 19th century, the large-scale Leblanc process, producing synthetic sodium sulfate as a key intermediate, became the principal method of soda-ash production.[7]