Definition of: Seidlitz powder

(sed′lits)
An aperient powder consisting of two separate parts: tartaric acid and sodium bicarbonate mixed with Rochelle salt: a mild cathartic used by dissolving separately, mixing the solutions, and drinking while effervescing: also called Rochelle powder. [from Seidlitz; so called because of its aperient property, similar to that of the water from the spring there]