cenwatchglass:

Bismuth crystal illustrating the many iridescent refraction hues of its oxide surface (Alchemist-hp + Richard Bartz / Wikimedia Commons).

Bismuth is the heaviest nonradioactive element and is essentially a nontoxic neighbor of lead and thallium in the periodic table. It is mined as bismuth oxide (Bi₂O₃, also known as bismite) or bismuth sulfide (Bi₂S₃, bismuthinite), and the brittle, silvery elemental form is one of a few substances (water is another) for which the solid is less dense than the liquid. Although bismuth has been extensively used in alloys, pharmaceuticals, electronics, cosmetics, pigments, and organic, the chemistry of bismuth is perhaps the least well established of the group-15 elements (known as the pnictogens). Compounds of bismuth typically have low solubility in most solvents, so that definitive formula assignments are usually based on X-ray diffraction studies of crystalline samples that have been isolated in small or indefinite quantities. Most isolated compounds are unique rather than members of a series of related compounds illustrating fundamental chemical trends. 

The bioutility of bismuth compounds has a 250-year history that includes numerous medicinal applications; however, the mechanisms of bioactivity are not understood. Moreover, as for most compounds of bismuth, the chemical characterization of biorelevant complexes remains incomplete. Although the “heavy metal” designation has impeded application of bismuth chemistry in medicine, two compounds have been extensively used for gastrointestinal medication for decades. Pepto-Bismol contains bismuth subsalicylate, and De-Nol contains colloidal bismuth subcitrate. The use of these compounds for the treatment of travelers’ diarrhea, non-ulcer dyspepsia, nonsteroidal anti-inflammatory drug damage, and various other digestive disorders extends from the previous use of bismuth compounds in the treatment of syphilis and tumors, in radioisotope therapies, and in the reduction of the renal toxicity of cisplatin.

-Neil Burford

It’s Elemental: Bismuth

Chemical & Engineering News, September 8, 2003

(via cenwatchglass)