Mubtakkar
From dKosopedia
A mubtakkar is a binary cyanide gas generator that is easily portable, contains no components that are in themselves greatly toxic or otherwise dangerous to those transporting the device, but nevertheless capable of generating sufficient quantities of cyanide gas to flood a subway system or other such target.
The word "mubtakkar" is found both in Arabic and in Farsi. In the former it means "the invention," and in the latter it means "the initiative." It works rather like the epoxy glues that come in a kind of dual syringe with two cylinders and two linked plungers. The materials will not harden or otherwise react chemically while separated, but when the plunger is pushed equal amounts of the two glue components are ejected. They then get mixed and harden into a very strong adhesive. The mubtakkar also consists of two cylinders, one of which contains a commercially available compound used for rodent poison, sodium cyanide, and the other of which contains some chemical compound that will readily give up its hydrogen in combining with the cyanide in the sodium cyanide. When the two components are mixed together, hydrogen cyanide is formed. Hydrogen cyanide turns to gas at a relatively low temperature. In its gaseous form it is highly lethal to humans who inhale it.
Plans for this device were discovered as one result of a security operation performed in Saudi Arabia by a joint Saudi and American counter-terrorism unit.
For further information, see Ron Suskind's The One Percent Doctrine, p. 192ff.