Insoluble Saccharin, chemically known as 1,2-benzisothiazol-3(2H)-one 1,1-dioxide, is the water-insoluble acid form of saccharin. Unlike its sodium and calcium salt counterparts, acid saccharin has very limited solubility in water (approximately 0.35 g/100 mL at 25°C), making it suitable for specialized applications in chewable tablets, toothpaste, and lipophilic food systems. It is approved as a food additive under E954 and remains one of the oldest commercially produced artificial sweeteners, discovered in 1879.