By Richard J. Green
This Foreword will appear in the book by John C. Zimmerman entitled Holocaust Denial: Demographics, Testimonies and Ideologies, University Press of America which will be published in 2000.
The agent of mass murder in the homicidal gas chambers of Auschwitz and Birkenau was a product known as Zyklon B. The active ingredient in Zyklon B was the highly toxic compound hydrogen cyanide (HCN). In 1994, the Institute for Forensic Research Cracow (herein referred to as the IFFR, elsewhere as the IFRC) published a detailed study of the cyanides present in the homicidal gas chambers of Auschwitz and Birkenau. This study showed unequivocally the presence of cyanide in all the facilities tested in which the historical record shows that gassing took place. In contrast, they found no traces of cyanide within their detection limits (3-4 µg/kg) in prisoner barracks in which no homicidal gassing occurred. This introduction to the report will attempt to give some context for the lay reader to better understand the implications of the report.
Holocaust deniers often claim that the so-called forensic reports of Leuchter, Rudolf and others prove the impossibility of homicidal gassings at Auschwitz and Birkenau. A central point of their argument is that their studies apparently show that delousing chambers, in which Zyklon B was used, have much higher concentrations of cyanide compounds present than do the homicidal gas chambers. Of course such presumes that their studies were conducted honestly and with good technique. Zimmerman,1Pressac,2and perhaps others have shown that such a presumption is unwarranted. Even if one takes the reports of Leuchter and others at face value, however, there is a crucial problem with their studies that is addressed in the study of the IFFR. This problem centers around a class of compounds called the iron blues, a representative example of which is Prussian blue.
Hydrogen cyanide and most of its salts are readily soluble in water and thus extremely susceptible to weathering, Prussian blue on the other hand is extremely insoluble. If Prussian blue were to form in a building exposed to hydrogen cyanide, it would remain present at high concentration while other compounds of cyanide would gradually weather away. It has long been known that some of the delousing chambers exhibit obvious blue staining, whereas the remains of the homicidal chambers at Auschwitz and Birkenau do not. Comparing the cyanide content of material from the delousing chambers that exhibits this blue staining and material from homicidal chambers that do not exhibit this staining, may show that the blue staining is indeed a cyanide compound, but it does not show the homicidal gas chambers were not exposed to HCN. This issue is explored in some depth in several articles available at the website of the Holocaust History Project (THHP).3 Here I only summarize those findings and explain their implications for the IFFR study.
It is shown in great detail in the above-mentioned articles that the conditions in the gas chamber would have made the formation of Prussian blue in significant quantities improbable. A building in which Prussian blue formed would have much higher levels of detectable total cyanides than a building in which Prussian blue did not form. Recall the Prussian blue is much less susceptible to weathering than other cyanides; so it is no surprise if buildings with blue staining have more cyanides than those without.
What is the right experiment to do? Detecting total cyanides appears to be a probe for the likelihood of Prussian blue formation and not a probe for exposure to cyanide. The correct procedure is to use a method of detecting cyanides that discriminates against the detection of Prussian blue. If any cyanides other than Prussian blue have survived the weathering process, they will be present in small concentrations. They need to be detected with an extremely sensitive technique.
The IFFR conducted an experiment according to the correct procedure. They write:
J. Bailer [see IFFR ref. 1] writes in the collective work "Amoklauf gegen die Wirklichkeit" that formation of Prussian blue in bricks is simply improbable; however, he takes into consideration the possibility that that the walls of the delousing room were coated with paint. It should be added that this blue coloration does not appear on the walls of all the delousing rooms.
We decided therefore to determine the cyanide ions using a method that does not induce the breakdown of the composed ferrum cyanide complex (this is the blue under discussion) and which fact we had tested before on an appropriate standard sample.
It should be noted that whereas formation of Prussian blue was unlikely in the homicidal gas chambers owing to conditions such as the frequent washing with water, exposure to carbon dioxide, and the short exposure time, the conditions in the delousing chambers were quite different and it is not improbable that exposure to cyanide could be responsible for the blue staining there. These issues are discussed in more detail in the aforementioned articles on the Holocaust History Project web site. The important point is that detection of total cyanides is not a reliable marker for exposure to cyanides owing to the complexities of Prussian blue formation. In other words, by discriminating against the detection of Prussian blue, the IFFR did the correct experiment. Note also the necessity of using a much more sensitive method of detection of cyanides. Leuchter and Rudolf report a detection limit of about 1 mg/kg and in fact dispute the reliability of some of their own measurements showing cyanide concentrations above that. Recall that the bulk of the cyanides that they detected were in a form similar to Prussian blue. The IFFR used a much more sensitive method. Their sensitivity was 3-4µg/kg, i.e., 300 times more sensitive. Even so, beforehand they were not confident that they would detect any cyanides other than the Prussian blue compounds because of the likelihood that these other cyanides would have weathered away.
To insure the reliability of their measurements, the IFFR introduced standards with a known cyanide content into each set of determinations. As well as samples from the homicidal gas chambers they collected control samples from dwelling accomodations "which were probably fumigated with Zyklon B only once (in connection with the typhoid [sic] epidemic in 1942)." The samples were collected and analyzed by two different teams to insure objectivity. The results of the study are definitive:
The results of the analyses are presented in Tables I-IV. They unequivocally show that the cyanide compounds occur in all the facilities that, according to the source data, were in contact with them. On the other hand, they do not occur in dwelling accomodations, which was shown by means of control samples.
Thus the chemical claims of the Leuchter Report are utterly refuted. The IFFR did some additional studies to understand why some construction materials kept their (non-Prussian blue) cyanides whereas other materials did not. They found that mortar and/or wet materials tended to accumulate cyanides, whereas brick was less likely to do so. Perhaps, the important point to realize here is that the IFFR had legal access to collect samples and could scrape their samples from areas likely to have been sheltered from weathering.
Before concluding it is worth mentioning a couple of minor issues. First, the IFFR referred to a typhoid epidemic when they doubtlessly meant a typhus epidemic. Second, the support for Zyklon B is referred to unambiguously as diatomaceous earth. Zyklon was manufactured with many different solid supports. 4, of note was the use of "Erco" a gypsum material. 5
The conclusion is obvious. Leuchter and other Holocaust deniers performed a "forensic analysis" that even had it been conducted straightforwardly and honestly was based upon incorrect premises. When real scientists approached the problem using appropriate methods and reasoning they were able to detect unambiguously, what we already knew to be the case from the historical record, viz., the gas chambers of Auschwitz and Birkenau were indeed exposed to cyanide.
The Report of the IFFR is presented here. Some minor editing has been done, but no substantive changes have been made.
Leuchter, Rudolf, and the Iron Blues, by Richard J. Green at http://www.holocaust-history.org/auschwitz/chemistry/blue/, and The Chemistry of Auschwitz by Richard J. Green at http://www.holocaust-history.org/auschwitz/chemistry/
Richard J. Green earned his PhD in physical chemistry from Stanford University in California in 1997. He is currently a volunteer with the Holocaust History Project.