page_title: Leuchter report
section_title: Prussian blue
hierarchical_section_title: Leuchter report / Claims and criticism / Prussian blue
caption_attribution_description: Polski: Komora żelbetonowa, przystosowana do uśmiercania więźniów tlenkiem węgla. Tlenek węgla doprowadzano rurą z kabiny ss-mana. Używano tu także cyklonu B English: Reinforced concrete chamber, designed for killing prisoners by carbon monoxide. Carbon monoxide was fed with a tube from the SS-man's booth. It also used Zyklon B.
context_page_description: The Leuchter report is a pseudoscientific document authored by American execution technician Fred A. Leuchter, who was commissioned by Ernst Zündel to defend him at his trial in Canada for distributing Holocaust denial material. Leuchter compiled the report in 1988 with the intention of investigating the feasibility of mass homicidal gassings at Nazi extermination camps, specifically at Auschwitz. He travelled to the camp, collected multiple pieces of brick from the remains of the crematoria and gas chambers, brought them back to the United States, and submitted them for chemical analysis. At the trial, Leuchter was called upon to defend the report in the capacity of an expert witness; however during the trial, the court ruled that he had neither the qualifications nor experience to act as such.
  Leuchter cited the absence of Prussian blue in the homicidal gas chambers to support his view that they could not have been used to gas people. However, residual iron-based cyanide compounds are not a categorical consequence of cyanide exposure.
context_section_description: Leuchter's opposition to the possibility of homicidal gassings at Auschwitz relies on residual cyanide remains found in the homicidal gas chambers and delousing chambers at Auschwitz. While both facilities were exposed to the same substance (Zyklon B), many of the delousing chambers are stained with an iron based compound known as Prussian blue, which is not apparent in the homicidal gas chambers. It is not only this disparity that Leuchter cites, but accordingly from his samples (which included measurements of it) that he claims he measured much more cyanide in the delousing chambers than in the gas chambers, which he argues is inconsistent between the amounts necessary to kill human beings and lice. This argument is often cited by Holocaust deniers, and similar claims are also made by Germar Rudolf.
  According to Richard J. Green:
  In order for Leuchter or Rudolf to demonstrate the significance of their findings, it is necessary for them to prove the necessity of Prussian blue formation under the conditions that the homicidal gas chambers were operated. Showing that the delousing chambers have Prussian blue and that the homicidal gas chambers do not, proves nothing, if it cannot be shown that conditions in the gas chambers were such as to produce Prussian blue.
  In other words, Green states that Leuchter failed to show that Prussian Blue would have been produced in the homicidal gas chambers in the first place—meaning its absence is not in itself proof that no homicidal gassings took place.
  The problem with Prussian blue is that it is by no means a categorical sign of cyanide exposure. One factor necessary in its formation is a very high concentration of cyanide. In terms of the difference between amounts measured in the delousing chambers and homicidal gas chambers, critics explain that the exact opposite of what deniers claim is true. Insects have a far higher resistance to cyanide than humans, with concentration levels up to 16,000ppm (parts per million) and an exposure time of more than 20 hours (sometimes as long as 72 hours) being necessary for them to succumb. In contrast, a cyanide concentration of only 300ppm is fatal to humans in a matter of minutes. This difference is one of the reasons behind the concentration disparity. Another exceedingly sensitive factor by which very small deviances could determine whether Prussian blue may form is pH. pH could be affected by the presence of human beings. Also, while the delousing chambers were left intact, the ruins of the crematoria at Birkenau had been exposed to the elements for over forty years by the time Leuchter collected his samples. This would have severely affected his results, because unlike Prussian blue and other iron based cyanides, cyanide salts are highly soluble in water.
  Since the formation of Prussian blue is not an unconditional outcome of exposure to cyanide, it is not a reliable indicator. Leuchter and Rudolf claim to have measured much more cyanide in the delousing chambers than in the homicidal gas chambers, but since they did not discriminate against an unreliable factor, Green maintains that instant bias is introduced into their experiments. Similarly, Rudolf acknowledges that Prussian blue does not always form upon exposure to cyanide and is thus not a reliable marker, yet continues to include the iron compounds in his analysis. Green describe this as "disingenuous". Since a building that contains Prussian blue staining would exhibit much higher levels of detectable cyanides than one without any, Green writes that Leuchter's and Rudolf's measurements reveal nothing more than what is already visible to the naked eye.
caption: Gas chamber in Majdanek concentration camp with blue residue
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