Holmium shards

20 grams of holmium metal shards

Holmium is a lanthanide with the atomic number 67 and the symbol Ho. It is a gray metal that is reactive and slightly magnetic at room temperature. Holmium is difficult to find and somewhat expensive, but has some interesting properties regarding its magnetism and narrow absorption bands.

Properties Edit

Physical properties Edit

As a lanthanide, holmium resembles is neighboring elements strongly. It is paramagnetic, enough to be visibly lifted by a neodymium magnet. Its trivalent salts show dramatic color changes depending on the light source: they appear yellow in natural daylight, but vividly pink under compact fluorescent lighting, and very slightly pink under tube lighting.

Chemical properties Edit

Holmium is a strong reducing agent and will readily react with weak oxidizers. It burns in air with a yellow[1] or green[2] flame to form holmium oxide. (The green color is likely the true color of burning holmium; the yellow color may be black-body radiation from the products.) Holmium is almost exclusively trivalent, and it is extremely difficult to reduce or oxidize holmium salts. It also reacts with the halogens to form colorful halides, which have the same color-changing properties under different light sources.

Holmium trifluoroacetate and holmium trifluoromethanesulfonate (triflate) are relatively recently discovered catalysts for organic reactions. Even though they are Lewis acids, they do not hydrolyze readily and can be used in numerous solvents. Other lanthanide triflates have been investigated for catalytic activity.

Availability Edit

Holmium is more common than iodine on Earth, but it is very hard to find. For a lanthanides, it is cheaper than some other metals. One source for holmium, as well as other rare earth metals, is Metallium. It is sold in 5 gram and 50 gram sizes, as well as rods, ampoules, and coins. Holmium and its compounds are occasionally sold on eBay as well.

Projects Edit

  • Color changing crystals
  • Magnet polepieces?

Safety Edit

Storage Edit

Bulk holmium metal is stable in air indefinitely. As a powder or fine turnings, it may be extremely flammable, and should be kept away from ignition sources.

Toxicity Edit

Holmium and its compounds have not been thoroughly investigated for toxicity, but no adverse effects have been reported from exposure.

Flammability Edit

Small pieces of holmium metal or powder are flammable. Class D fire extinguishers should be readily available when working with large amounts of holmium near an open flame. Water should never be used to extinguish burning holmium, as it will aggravate the flame.

References Edit