What Is Red Mercury?

The science newsgroups have been abuzz with tales of a 2-kiloton yield Russian red mercury fusion device, theoretically in the possession of terrorists. This, of course, prompts the questions: What is red mercury? The answer to this question depends largely on who you ask. Is red mercury real? Absolutely, but definitions vary. Cinnabar/vermillion is the most common answer. However, the Russian tritium fusion bomb is more interesting.

What Is Red Mercury?

1. Cinnabar/Vermillion
   Cinnabar is naturally occurring mercuric sulfide (HgS), while vermillion is the name given to the red pigment derived from either natural or manufactured cinnabar.
2. Mercury (II) Iodide
   The alpha crystalline form of mercury (II) iodide is called red mercury, which changes to the yellow beta form at 127 C.
3. Any Red-Colored Mercury Compound Originating in Russia
   Red can also be used in the Cold War definition of red, meaning communist. It is doubtful that anyone today is using red mercury in this manner, but it's a possible interpretation.
4. A Ballotechnic Mercury Compound Presumably Red in Color
   Ballotechnics are substances that react very energetically in response to high-pressure shock compression. Google's Sci.Chem group has had a lively ongoing discussion about the possibility of an explosive form of mercury antimony oxide.
   According to some reports, red mercury is a cherry-red semi-liquid that is produced by irradiating elemental mercury with mercury antimony oxide in a Russian nuclear reactor. Some people think that red mercury is so explosive that it can be used to trigger a fusion reaction in tritium or a deuterium-tritium mixture. Pure fusion devices don't require fissionable material, so it's easier to get the materials needed to make one and easier to transport said materials from one place to another.
   Other reports refer to a documentary in which it was possible to read a report on Hg₂Sb₂0₇, in which the compound had a density of 20.20 Kg/dm³. It is plausible that mercury antimony oxide, as a low-density powder, may be of interest as a ballotechnic material. The high-density material seems unlikely. It would also seem unreasonably dangerous (to the maker) to use a ballotechnic material in a fusion device. One intriguing source mentions a liquid explosive, HgSbO, made by DuPont laboratories and listed in the international chemical register as number 20720-76-7. 
5. A Military Code Name for a New Nuclear Material​
   This definition originates from the extraordinarily high prices commanded and paid for a substance called red mercury that was manufactured in Russia. The price ($200,000-$300,000 per kilogram) and trade restrictions were consistent with a nuclear material as opposed to cinnabar.