Bismuth

A broken bismuth hopper crystal, showing iridescence.

Bismuth is a chemical element with symbol Bi and atomic number 83. It is a post-transition metal, grey and dense. This metal is known to be among the least toxic heavy metals.

Properties

Chemical

Bismuth is stable to both dry and moist air at ordinary temperatures. When red-hot, it reacts with water to make bismuth trioxide.

2 Bi + 3 H₂O → Bi₂O₃ + 3 H₂

Bismuth dissolves in concentrated sulfuric acid to make bismuth(III) sulfate and sulfur dioxide.

2 Bi + 6 H₂SO₄ → 6 H₂O + Bi₂(SO₄)₃ + 3 SO₂

Bismuth reacts with halogens to produce bismuth halides. Unlike bismuth trifluoride and bismuth triiodide, bismuth trichloride and bismuth pentafluoride rapidly hydrolyse in moist air and water. Bismuth will react with most acids, but oxygen or hydrogen peroxide has to be present to oxidize the metal.

Physical

Bismuth is a brittle white-silver metal in its pure form. It will oxidize in air to form an iridescent hue, under certain circumstances, showing many colors from yellow to blue. It has the lowest thermal conductivity of all known metals and it is the most diamagnetic pure element. Similar to antimony, gallium, germanium and silicon, bismuth is denser in the liquid phase than the solid (like ice), expanding 3.32% on solidification.

Availability

Bismuth is present as bismuth subsalicylate in Pepto-Bismol. It can be extracted from the compound, as shown here.

Large chunks of metal can be bought as Hopper crystals, that display beautiful iridescence.

Bismuth is found in certain electronics, mostly as lead-free solder. The solder that binds the ceramic lid to the CPU appears to be mostly of bismuth, as after melting it and letting it cool in open air it displays the typical iridescence.

Preparation

Bismuth can be extracted from Pepto-Bismol, by adding acid and then reducing the metal with either aluminium or other reducing metal.

Projects

• Making bismuth crystals
• Levitation with magnets

Handling

Safety

Unlike it's surrounding metals (lead, antimony, polonium), bismuth and bismuth compounds have low toxicity. Overexposure to bismuth, however, can result in the formation of a black deposit on the gums, known as a "bismuth line".

Some of its compounds, such as bismuth chloride will hydrolyze in moist air and is corrosive to skin, so protection is required when handling the compound.

Storage

Bismuth does not require special storage. Hopper crystals can be displayed on any shelf or table.

Disposal

It's best to try to recycle the bismuth and avoid dumping it in the environment.