Bismuth is a chemical element with the symbol Bi and atomic number 83. The free element is 86% as dense as lead. It is a brittle metal with a silvery-white color when freshly produced, but surface oxidation can give it an iridescent tinge in numerous colours.   Bismuth Carbonate is a water insoluble Bismuth source that can easily be converted to other Bismuth compounds, such as the oxide by heating (calcination). Carbonate compounds also give off carbon dioxide when treated with dilute acids.     Uses. It is highly radiopaque and for example is used as a filler in radiopaque catheters which can be seen by x-ray. In modern medicine, bismuth subcarbonate has been made into nanotube arrays that exhibit antibacterial properties. It is also used in fireworks to make Dragon's eggs.