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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Red mercury | 2/4 | https://en.wikipedia.org/wiki/Red_mercury | reference | science, encyclopedia | 2026-05-05T09:30:57.782261+00:00 | kb-cron |
== Analysis == Several common mercury compounds are indeed red, such as mercury sulfide (from which the bright-red pigment vermilion was originally derived), mercury(II) oxide (historically called red precipitate), and mercury(II) iodide. No use for any of these compounds in nuclear weapons has been publicly documented. "Red mercury" could also be a code name for a substance that contains no mercury at all. A variety of different items have been chemically analyzed as putative samples of "red mercury" since the substance first came to the attention of the media, but no single substance was found in these items. A sample of radioactive material was seized by German police in May 1994. This consisted of a complex mixture of elements, including about 10% by weight plutonium, with the remainder consisting of 61% mercury, 11% antimony, 6% oxygen, 2% iodine and 1.6% gallium. The reason why somebody had assembled this complex mixture of chemicals is unknown; equally puzzling was the presence of fragments of glass and brush bristles, suggesting that someone had dropped a bottle of this substance and then swept it up into a new container. In contrast, an analysis reported in 1998 of a different "red mercury" sample concluded that this sample was a non-radioactive mixture of elemental mercury, water and mercury(II) iodide, which is a red colored chemical. Similarly, another analysis of a sample recovered in Zagreb in November 2003 reported that this item contained only mercury. One formula that had been claimed previously for red mercury was Hg2Sb2O7 (mercury(II) pyroantimonate), but no antimony was detected in this 2003 sample.
== Explanations == Red mercury was described by many commentators, and the exact nature of its supposed working mechanism varied widely among them. In general, however, none of these explanations appear to be scientifically or historically supportable.
=== Background === Traditional staged thermonuclear weapons consist of two parts, a fission "primary" and a fusion/fission "secondary". The energy released by the primary when it explodes is used to (indirectly) compress the secondary and start a fusion reaction within it. Conventional explosives are far too weak to provide the level of compression needed. The primary is generally built as small as possible, because the energy released by the secondary is much larger, and thus building a larger primary is generally inefficient. There is a lower limit on the size of the primary, known as the critical mass. For weapons grade plutonium, this is around 10 kg (22 lb). This can be reduced through the use of neutron reflectors or clever arrangements of explosives to compress the core, but these methods generally add to the size and complexity of the resulting device. Because of the need for a fission primary and the difficulty of purifying weapons-grade fissile materials, the majority of arms control efforts to limit nuclear proliferation rely on the detection and control of the fissile material and the equipment needed to obtain it.
=== Shortcut to fissionable material === A theory popular in the mid-1990s was that red mercury facilitated the enrichment of uranium to weapons-grade purity. Conventionally, such enrichment is usually done with Zippe-type centrifuges, and takes several years. Red mercury was speculated to eliminate this costly and time-consuming step. Although this would not eliminate the possibility of detecting the material, it could escape detection during enrichment as the facilities hosting centrifuges normally used in this process are large and require equipment that can be fairly easily tracked internationally. Eliminating such equipment would in theory greatly ease the construction of a clandestine nuclear weapon.
=== Shortcut to fusible material === A key part of the secondary in a fusion bomb is lithium-6-deuteride. When irradiated with high-energy neutrons, Li-6 creates tritium, which mixes with the deuterium in the same mixture and fuses at a relatively low temperature. Russian weapon designers have reported (1993) that red mercury was the Soviet codename for lithium-6, which has an affinity for mercury and tends to acquire a red colour due to mercuric impurities during its separation process.