Bismuth
. Bismuth, symbol Bi, rare metallic element that has a pinkish tinge. The atomic number of bismuth is 83; it is in group 15 (or Va) of the periodic table (see Periodic Law ). Bismuth was known in ancient times, but until the middle of the 18th century, it was confused with lead, tin, and zinc. Ranking about 73rd in natural abundance among the elements in the earth's crust, it is about as rare as silver. Most industrial bismuth is obtained as a by-product. Chemically, bismuth is a typical metal. In compounds it has valences of +3 or +5, the compounds of trivalent bismuth being more stable. There are several nitrates, notably bismuth nitrate or bismuth trinitrate; and bismuth nitrate pentahydrate. The latter form decomposes into basic bismuth nitrate. Basic bismuth nitrate is also known as bismuth oxynitrate, or bismuthyl nitrate, and may be used in medicine and cosmetics. Other names for basic bismuth nitrate are pearl white and Spanish white. Bismuth expands on solidifying; this un