Zyklon B (German pronunciation: [tsykloːn ˈbeː]; also spelled Cyclon B or Cyclone B) was the trade name of a cyanide-based pesticide infamous for its use by Nazi Germany against human beings in gas chambers of extermination camps during the Holocaust.
It consisted of hydrogen cyanide (prussic acid, Blausäure in German, hence B), a stabilizer, and a warning odorant that was impregnated onto various substrates, typically small absorbent pellets, fibre discs, or diatomaceous earth. Zyklon B was stored in airtight containers; when exposed to air, the material released gaseous hydrogen cyanide (HCN).
Zyklon B was originally developed during the 1920s as an insecticide by Walter Heerdt, Bruno Tesch and Gerhard Peters, at the Kaiser Wilhelm Institute for Physical Chemistry and Elektrochemistry at Berlin-Dahlem, whose director at that time was Dr. Fritz Haber, a world-renowned chemist and recipient of the 1918 Nobel Prize in Chemistry for his discovery of the method for the organic synthesis of ammonia (see Haber Process).
In early 1942, Zyklon B had been selected by the Nazi Regime as the preferred extermination tool for both the Auschwitz-Birkenau and Majdanek extermination camps during the Holocaust. The chemical claimed the lives of roughly 1.2 million people in these camps.
Degesch played a key role in the manufacturing of Zyklon B in World War II. Many German companies had stock in Degesch, but all eventually sold their shares to the chemical giant Degussa (now known as Evonik) in the early 1920s. Degussa developed the process to manufacture Zyklon B in "crystals" (actually silica gel absorbent chunks), as it was used during World War II. To raise capital, Degussa split its controlling interest of Degesch with IG Farben in 1930: both companies held a 42.5% share in Degesch, with the remaining 15% held by the Th. Goldschmidt AG of Essen.
Degesch's role at this point was limited to acquiring patents and intellectual property: it did not itself produce Zyklon B. The manufacture of Zyklon B was handled by the Dessauer Werke für Zucker and Chemische Werke, which acquired the stabilizer from IG Farben, the warning agent from Schering AG and the prussic acid from Dessauer Schlempe and assembled them into the final product. This company extracted prussic acid from the waste products of the sugar beet refining process. From 1943 to 1945, the Kaliwerke, from the Czech town of Kolin, also supplied prussic acid to the Dessauer Werke.
Upon production, Zyklon B was sold by Degesch to Degussa. To cut costs, Degussa sold the marketing rights of Zyklon B to two intermediaries: the Heerdt and Linger GmbH (Heli) and Tesch and Stabenow (Tesch und Stabenow, Internationale Gesellschaft für Schädlingsbekämpfung m.b.H., or Testa) of Hamburg. Both suppliers split their territory along the Elbe river, with Heli handling the clients to the west and Testa doing the same in the east.
From 1929 onwards the U.S. used Zyklon B to disinfect the freight trains and clothes of Mexican immigrants entering the US. Farm Securities Administration photographer Marion Post Wolcott recorded the use of cyanide gas and Zyklon B by the Public Health Service at the New Orleans Quarantine Station during the 1930s.
Zyklon B was used by Nazi Germany to poison prisoners in the gas chambers of their network of extermination camps throughout Europe. Zyklon B was used at Auschwitz Birkenau, Majdanek, Sachsenhausen and one of the Operation Reinhard camps. At the other extermination camps, Carbon monoxide from engine exhaust was used in the gas chambers or mobile gas vans. Most of the victims were Jews and the Zyklon B gas became a central symbol of the Holocaust.
In January or February 1940, 250 Gypsy children from Brno in the Buchenwald concentration camp were used as guinea pigs for testing the Zyklon B gas. On September 3, 1941, around 600 Soviet prisoners of war and 250 sick Polish prisoners were gassed with Zyklon B at Auschwitz camp I; this was the first experiment with the gas at Auschwitz. The experiments lasted more than 20 hours.
According to Rudolf Höss, commandant of Auschwitz, bunker 1 held 800 people, and bunker 2 held 1,200. Once the chamber was full, the doors were screwed shut and solid pellets of Zyklon B were dropped into the chambers through vents in the side walls, releasing the cyanide gas. Those inside died within 20 minutes; the speed of death depended on how close the inmate was standing to a gas vent, according to Höss, who estimated that about one third of the victims died immediately. Johann Kremer, an SS doctor who oversaw the gassings, testified that: "Shouting and screaming of the victims could be heard through the opening and it was clear that they fought for their lives." When they were removed, if the chamber had been very congested, as they often were, the victims were found half-squatting, their skin colored pink with red and green spots, some foaming at the mouth or bleeding from the ears.
After the war, two directors of Testa – Bruno Tesch and Karl Weinbacher – were tried by a British military court and were executed for their part in supplying the chemical.
The use of the word Zyklon (German for cyclone) continues to prompt angry reactions from Jewish groups. In 2002, both Bosch Siemens Hausgeräte and Umbro were forced to withdraw from attempts to use or trademark the term for their products.
Holocaust deniers say that Zyklon B gas was not used in the gas chambers, relying as evidence on the low levels of Prussian blue residue in samples of the gas chambers found by Fred A. Leuchter, which Leuchter dismissed as the results of general delousing of buildings. Leuchter's negative control, a sample of gasket material taken from a different building in the camp, registered as having no such cyanide residue. The manager of the analytical laboratory hired by Leuchter states in an interview in Errol Morris' film Mr. Death: The Rise and Fall of Fred A. Leuchter, Jr., that Leuchter's thick samples of brick would have greatly diluted the cyanide residue, which forms only an extremely fine layer on the walls and cannot penetrate.
In 1994, the Institute for Forensic Research in Kraków re-examined this claim on the grounds that formation of Prussian blue by exposure of bricks to cyanide is not a highly probable reaction . Using more sophisticated microdiffusion techniques, they tested 22 samples from the gas chambers, delousing chambers (as positive controls), and living quarters (as negative controls), finding cyanide residue in both the delousing chambers and the ruins of the gas chambers but none in the ruins of the living quarters.