Bismuth subnitrate is a basic bismuth nitrate, commonly represented as a hydrated basic salt of bismuth and nitric acid. It appears as a white to off-white, heavy, crystalline or amorphous powder and is practically insoluble in water and most organic solvents. On heating or in acidic media, it decomposes to form bismuth oxide and soluble bismuth nitrate species. Due to its chemical stability, low solubility, and low toxicity relative to other heavy-metal salts, bismuth subnitrate is widely used in pharmaceutical preparations, analytical chemistry, and as a precursor for other bismuth compounds.