Supplement 4: Zyklon B and Gas Detectors in Birkenau Crematorium II

The main content of this supplement first appeared in print in the

Journal of Historical Review, vol. 16, no. 5, Sept.-Oct. 1997, pp. 24-30.

Zyklon B

In The Hoax of the Twentieth Century, I remarked that typhus was a great killer for the Germans in World War I, giving a reference published shortly after that war.[645] The typhus of World War I, like that of World War II, was carried by lice. In response to this specific problem, the German company DEGESCH (Deutsche Gesellschaft für Schädlingsbekämpfung - German Pest Control Co.) developed the Zyklon B pesticide[646] and made it available for commercial use in 1923.

Zyklon B, referred to here merely as Zyklon, is a very effective pesticide consisting of liquid hydrogen cyanide (HCN, an acid) absorbed into some inert material such as wood pulp, with an irritant added to warn bystanders of its presence. HCN is also called "prussic acid" and in German "Blausäure" (blue acid), because HCN tends to leave blue stains in the presence of iron compounds like rust; the resulting insoluble and non-toxic iron salt of HCN, Iron Blue, is commonly used in blue dyes.

In its gaseous or liquid form, HCN is very deadly and is used in American execution gas chambers, where it is traditionally generated by mixing an acid (normally sulfuric acid) with potassium cyanide or sodium cyanide, resulting in rapid release of HCN in its gaseous form.

HCN is useless as a battlefield gas because it is a true gas, slightly lighter than air, and disperses too rapidly for that application. World War I battlefield gases were actually dusts that hovered about the target area.

The pesticide Zyklon works somewhat differently. It is supplied in a very tightly sealed container. When a space (e.g. a barracks or building) is to be treated with it, that space is tightly sealed, and trained personnel empty cans of Zyklon on the floor, preferably spreading the Zyklon out as much as possible. They then leave the space, close it, and wait the time required for the liquid HCN to pass into the gaseous form by evaporation, fill the space, and kill the target pests. Then the space is opened and ventilated.

This is a very time consuming process because the evaporation is slow, and for safety reasons the time required for ventilation is lengthy. The boiling point of HCN is 25.6°C (78°F). That does not mean the space must have that ambient temperature in order for the gas to be released; water does not have to be brought to its boiling point in order to evaporate. However, the process is slow at any lower temperature and especially slow in winter temperatures.

An information booklet for Zyklon[647] gives typical times of 2-72 hours for the gassing process and at least 10 hours for ventilation; the former depends very much on the temperature and the target pests and the latter on the physical properties of the space and its contents. For example, clothing and bedding should be beaten even after ventilation.

Another step recommended at the end of a Zyklon gassing and ventilation process is the test for residual HCN gas. The typical test uses a mixture of copper acetate and benzidene acetate and test paper which turns dark blue if the HCN level is dangerously high. A temperature of at least 15°C (60°F) is required to perform this test, so there are many circumstances under which it cannot be performed.[648]

Use of Zyklon is inherently dangerous, and during the war there existed a German regulation that it could be used only by, or under license from, DEGESCH, which was officially responsible for training all operators using it.[649]

There have also been gas chambers designed specifically to use Zyklon to disinfest articles such as clothing with HCN, especially in Germany.[650] With few exceptions the interiors of these gas chambers are heated, in order to accelerate the development of the gaseous HCN from the liquid form, and for other reasons. Gaseous HCN is water soluble, so high temperature is desired to reduce moisture in the gas chamber. Also, lice and some other pests are easier to kill at higher temperatures, because their metabolism rates are higher. Desired temperatures are in the range 25-35°C (77-95°F).

In such gas chambers, the air/gaseous HCN mixture is expelled from the top when the gassing process is completed, for safety reasons and perhaps because fresh air that enters during the ventilation is cool and the warmer air/ HCN gas mixture tends to the top of the chamber (as already mentioned, gaseous HCN, by itself, is only slightly lighter than air).

A related point is that the standard German Zyklon gas chamber of the time used a circulatory system developed by DEGESCH. In this system the air/ HCN mixture is continually recirculated, i.e. it continually exits and re-enters the gas chamber. Circulation greatly reduces the length of time required to generate the gas from the Zyklon and work on the target pests. At the conclusion of the gassing, expulsion of the gas and the introduction of fresh air are accomplished by opening and closing the relevant ports in this circulatory system. Overall, a gas chamber with circulation is about three times more effective than one without, i.e. can do about three times more work.[651] The practical minimum time required to kill lice (among the most difficult and resistant creatures) with Zyklon is about 3/4 of an hour. In a heated gas chamber with circulation, a total time of about an hour for gas generation and killing of the lice, followed by a ventilation period of about 20 minutes, is attainable under practical operational conditions.[652]

The best material for a gas chamber using HCN is steel. If bricks or concrete are used, then the interiors must be coated with a sealant to prevent retention of the gas in the walls of the gas chamber.[653]

Gas Detectors

The extermination legend claims that the pesticide Zyklon B was used to exterminate Jews in a "gas chamber" within Auschwitz Crematorium II at Birkenau (see Fig. 33), specifically, in Leichenkeller 1 (morgue cellar 1), whose alleged real purpose was concealed by being so designated.

In his 1989 book, Pressac[654] remarked on a telegram of 26 Feb. 1943 from the Auschwitz construction department to the furnace maker Topf. At that date, the construction of Crematorium II was nearing completion. The telegram requested delivery of 10 gas detectors for Crematorium II, as had been earlier discussed. The specific gas to be detected was not stated, but by a process of tortured reasoning, Pressac concluded that the detectors were for HCN gas, rather than for "the products of combustion, such as CO or CO2, in the furnace room", and classified this document as one of his so-called "criminal traces". Robert Faurisson wrote, in reply, that Pressac himself had solved this problem and that there was no reason to believe the detectors were for HCN.[655]

Pressac did more research and published a new book in 1993, in which he produced a document newly discovered in the recently opened Moscow archives.[656] It is a letter dated 2 March 1943 from the Topf company (by Senior Engineer Prüfer and a Topf colleague) to the Auschwitz construction department, and it shows that HCN was indeed the specific gas to be detected by the detectors. It reads:

"We confirm receipt of your telegram specifying 'Immediately send 10 gas detectors as agreed, price quote to follow.'

We hereby inform you that two weeks ago we inquired, of five different companies, concerning the residual HCN detection devices sought by you. We have received negative responses from 3 companies and 2 have not yet answered.

If

[Wenn] we receive information on this matter, we shall immediately contact you, in order to put you in touch with a company that makes these devices."

Faurisson's reply was that Zyklon B was used for delousing operations throughout the camp and of course in Crematorium II. Naturally HCN gas detectors would have been required in such operations, in which they are standard equipment.[657]

A Problem

In both cases Faurisson gave the simple, obvious replies that I would have given under the circumstances. However, I believe this interpretation is wrong, for reasons that may be seen by examining the document. The main obstacle to interpreting this letter in terms of Zyklon B is the roles of Topf and Prüfer.

Zyklon was a product of the DEGESCH company; Zyklon and associated equipment such as gas detectors and gas mask filters were also manufactured by other companies such as Tesch & Stabenow and Drägerwerke. At Auschwitz, delousing operations with Zyklon were such major and continuous tasks that there existed a special department, the Referat für Schädlingsbekämpfung (Pest Control Office), that conducted them. This department on occasion even communicated directly with DEGESCH.[658]

Topf was a furnace maker with crematorium ovens as a sideline and was the principal civilian contractor in the construction of crematoria at Auschwitz. Prüfer was the main Topf contact of the Auschwitz construction department and of course was not associated with the special SS delousing squads that regularly worked with Zyklon B. Why should Prüfer have been searching, indeed with great difficulty, for devices that were standard equipment for the delousing squads and were readily available from the DEGESCH and other companies, which had developed and supplied Zyklon? The standard DEGESCH detector for HCN required exposing a test paper and observing the color assumed. The Prüfer letter even implies that he does not know whether the desired devices exist, was confronting this specific need for the first time, and does not know very much about it, inferences that are very important in interpreting the letter. I do not believe the letter had anything to do with Zyklon.

There may however have been one connection between Topf and Zyklon. Robert Faurisson has brought to my attention an anti-revisionist, Pressac supporting book published in France in early 1997. A footnote declares:[659]

"The study of the history of the Topf and Sons company of Erfurt would be essential to show the progression to mass crime. Topf made, in the Twenties, crematoria but also grain silos. In the after sale services and maintenance for these silos, Topf also involved itself in HCN disinfestation and furnished all necessary material. Thus the two branches of activity of the firm converge in a striking manner toward the crematoria - gas chambers of Birkenau. On this particular sort of study, the works of Pressac are of the greatest utility, and it is in this way that they should be used."

The author gives no sources, but I think the claim of such Topf involvement with HCN, presumably via Zyklon, is quite plausible. Under conditions where Topf would have been the only company that a farmer dealt with in constructing his silo, it would have been natural for Topf to serve as retailer of supporting materials and equipment made by DEGESCH and other companies. However, such a Topf role had no bearing on conditions at Auschwitz in 1941-1945, where a special department regularly conducted operations with Zyklon. Their personnel would have been responsible for declaring when a treated facility was again safe to use. Is it plausible that Prüfer could have been involved in this when, as his letter shows, he didn't know very much about it?

There remains one possibility. Perhaps some unusual feature of the cremation process, not understood by the Zyklon delousing personnel, raised a novel problem with the Zyklon that Prüfer was asked to solve. I can't imagine such a feature, since cremation with coke seems basically like any other use of coke. However, if such an unusual feature existed, would it not have come up earlier in the six muffle crematorium, also supplied by Topf, that existed in the Stammlager or Auschwitz I? In 1942, this sole crematorium was working at capacity, and the disastrous typhus epidemics were being fought with Zyklon. However, the February to March 1943 correspondence marked the first confrontation of Prüfer with the problem involved. Some novel feature of Crematorium II had to be the problem.

It is also clear that the letter has nothing to do with gas detectors as defenses against chemical warfare. The German chemical warfare services were highly competent and organized and would not have sent a furnace maker on a quest for such equipment.

From one point of view, the problem raised has little to do with the "extermination" allegations. If the Zyklon were being used to kill people, rather than lice, then presumably the same specially trained squads would have been used or at least consulted, and the usual HCN gas detectors would have been used in the last stages of gassing operations. There would have been no problems in acquiring such standard equipment. Those who believe Zyklon was used for homicidal purposes should be as puzzled by this document as I was.

From another point of view, this problem is very relevant to the claim of "extermination", as explained below.

An Alternative Interpretation

The Topf letter of 2 March 1943 is strange, and for a while I suspected its authenticity. However, I have found an interpretation, which may be correct, and the main purpose of this article is to propose it. After I have done that, I shall return to the question of the relevance of this problem to the "extermination" allegations.

"HCN" is of course a compound of hydrogen, carbon, and nitrogen and may be generated whenever materials containing these elements are burned. For example, the fuel used for the crematorium ovens was coke, and it is well known that HCN gas is a possible by-product in the process of making coke from coal. However, there is apparently no danger of HCN release when coke, of whatever grade, is burned as a fuel; otherwise it would not be in such common use. HCN gas could not have been thus generated in the crematorium.

A remaining possibility is that HCN release was possible in the waste incinerator, which shared the chimney with the cremation ovens. Many materials may release HCN when burned. Among these are many fabrics, a highly relevant observation, because the waste incinerator was most likely used to incinerate used camp fabrics (e.g. inmate uniforms and bed linen and mattresses). For example, silk and wool can release HCN when burned, a fact that has been known since the Thirties.

As shown in Fig. 34, the chimney of Crematorium II was divided into three ducts. Six furnaces used this chimney, namely the waste incinerator and the five cremation furnaces (each with three muffles). The waste incinerator was on the opposite side of the chimney in relation to the cremation furnaces. These six furnaces used the three ducts on the basis of two per duct; thus, the waste incinerator shared one of the three ducts with one of the cremation furnaces (the flues leading from the furnaces to the chimney were underground).[660] The waste incinerator was also supplied by Topf,[661] and it could have been Prüfer's responsibility to take into account any HCN danger arising from it. Also, a gas detector differing from that used in the Zyklon delousing operations would seem fitting; perhaps a detector generating an audible alarm was desired.

While a concern for HCN release in combustion is routine today, it would have been novel in 1943, a fact that could explain the novelty for Prüfer, of the desire for an HCN detector. Another thing that could account for this novelty is that the waste incinerator design was itself novel. I have no expertise in the field, but I would think intuitively that a waste incinerator design sharing a chimney with other equipment, at which people are working, is dangerous.

The question of the quantities of HCN released in the burning of materials is complicated and depends on "the chemical nature of the material, temperature, oxygen availability, and burning time." Since HCN is itself combustible, it makes a difference whether the combustion is "static" or "dynamic", an example of the latter being when there is forced air blowing and the HCN is swept away from the hot zone before it can itself be decomposed in any way. However, HCN can be released under either condition. Another complication is that HCN can be released in the smoldering after a fire has been extinguished.[662]

The term "residual" that appears in the letter in question could apply to either released HCN that, ideally, would have been consumed during the incineration process but wasn't or to HCN released after incineration during smoldering. The chimney of Crematorium II used, as of 29 January 1943, a forced draft system based on suction, but on 25 March 1943, Topf ordered this system removed due to overheating of its motors.[663]

A Specific Possibility

It remains to suggest a specific potential source for HCN development in the waste incinerator. In wartime Germany, many articles had to be ersatz (artificial or synthetic), because of shortages of materials normally imported. Cotton was in very short supply, and little was used for fabrics. Wool was available but not in normal quantities. In fact, Germany relied heavily on the manufacture of rayon, and during the war, army uniforms contained as much as 65% rayon. One must assume concentration camp uniforms and other fabrics used in the camps had high rayon content. Could the incineration of such rayon have produced HCN gas? It may seem not, because rayon has no nitrogen in its chemical composition. In making these statements, I am using the word "rayon" in the normally accepted sense; rayon is regenerated cellulose made from natural cellulose extracted from materials such as cotton linters or wood pulp. Cotton was scarce in wartime Germany, so almost all rayon was made from wood pulp.[664]

The burning of rayon can generate HCN gas, if the rayon is impregnated with, but not chemically bound to, compounds of ammonia, which supply the necessary nitrogen. This was established some years ago by T. Morikawa, who conducted experiments that established that ammonia and its compounds, combined with "cellulosic materials", can indeed result in the evolution of HCN when burned. The general conclusion was that such evolution was about the same as for substances having nitrogen in their chemical compositions in comparable amounts.[665] It is of great relevance, for this discussion, that Morikawa's study of this point was motivated by the fact that ammonium compounds are added to many fabrics to make them flame retardant (this is sometimes called "fireproofing", but that cannot be done literally with ordinary fabrics). Thus, Morikawa's experiments used, as the source of nitrogen, diammonium phosphate, a common flame retardant for fabrics.

During World War II, diammonium phosphate was commonly used in Germany to make fabrics, particularly rayon, flame retardant. Two such products were marketed by I.G. Farben under the trade names Akaustan N and Akaustan N 1139. Another product, Akaustan K, used other ammonium compounds as the flame retardant.[666] A disadvantage of such flame retardants is that they are water soluble and gradually "leach" out when the fabrics are washed. Thus, such soluble flame retardants "are applied with the idea of periodic reprocessing in order to maintain the desired properties [by] simple immersion in aqueous solutions" of the retardant.[667] That is, washing is followed by immersion in a solution of the flame retardant substance, then drying out. Another defense against leaching, employed by the Germans, used sulfamide (strictly speaking sulfuryl amide, SO2(NH2)2) in conjunction with a standard waterproofing agent, thus making reprocessing unnecessary.[668] Sulfamide is obtained by treating sulfuryl chloride with ammonia, and one gets the impression from Morikawa that one could also expect evolution of HCN in burning of cellulose impregnated with it.

While I do not have a document that says so, I consider it very plausible that many concentration camp fabrics were treated with flame retardants for security reasons, i.e. to limit the effects of fires started by inmates. This would have been particularly the case with bed linens and mattress fillings. Thus, I am proposing the possibility that fabrics used in the camps, destined to be disposed of by incineration, were known to present a danger of evolution of HCN in such incineration.

The favored German process for rayon manufacture was the viscose, which is also the favored process today. However, two German factories used the older and simpler cuprammonium process. That the cuprammonium process involved a solution of ammonia does not appear relevant to the present problem. What may be relevant is that a price of its simplicity was that the cuprammonium process required celluloses of a high degree of purity. Thus, cotton linters were considered the standard cellulose source for cuprammonium rayon, but on account of wartime shortages, the two German cuprammonium factories used wood pulp instead. This resulted in an inferior quality rayon. Much of the cuprammonium rayon was used for army uniforms, but there were other uses, for example military upholstery, mattress fillings, and parachutes. I have no source saying that it was used in concentration camp fabrics, but in view of its inferior quality, this is a very admissible conjecture. One version of the cuprammonium rayon used for mattress fillings was impregnated with urea and formaldehyde, with ammonium nitrate as a catalyst, in order to impart springiness to it.[669] It is known that urea can cause some ammonium based flame retardants to react with cellulose, thus giving a fabric so treated resistance to leaching.[670]

Summary

In summary I am saying

- it is certain the Topf letter has nothing to do with Zyklon.

- It is almost certain that the HCN danger referred to arose from the waste incinerator. I would be astonished if it were shown that such was not the case.

- It is probable that the HCN detectors were wanted because of a potential danger of HCN development in the incineration of fabrics, particularly rayons treated with flame retardants. However, I am far from certain on this, and I will not be astonished if other materials, consumed in the waste incinerator, were shown to have been suspected by the Auschwitz management as potential sources of HCN development.

Observations

Above I promised to return to the question of the relevance of the problem treated here to the "extermination" allegations. The mass of documents shows that Auschwitz was a large concentration camp with a disastrous death rate, due mainly to typhus carried by lice. In response to such problems, the Germans made great use of the pesticide Zyklon B and constructed large crematoria. There are no records showing that Jews were "gassed" or "exterminated". That is clear, and it ought not be necessary to argue that such was not the case. The documentation is immense, and the physical facts concerning the camp are conclusive. For more detail, see the remarks I delivered at the 1992 IHR Convention on the death rates and the crematoria capacities at Auschwitz and other camps.[671]

Another approach uses the normal historical method; you study what the people of the time were doing. I have discussed elsewhere the trap that the historian Walter Laqueur got himself into by applying this normal historical method to Auschwitz.[672] For a more general and introductory discussion, see Faurisson's tutorial.[673]

For practical purposes, the entire "extermination" legend rests on the claim that Auschwitz was an "extermination camp" where about a million Jews were gassed with Zyklon B in otherwise designated rooms within the crematorium buildings. Since that is emphatically not what the historical record says, the promoters of the legend are highly selective in choosing documents, which Pressac calls "criminal traces," which, it is claimed, prove their thesis. The HCN gas detectors are one of the "criminal traces" on Pressac's pathetically short list.[674]

In historiography, there is an alternative and more commonplace description of Pressac's procedure with "criminal traces". It is bad historiography of the simplest sort: tendentious selection of a very small part of the data, resulting in grossly distorted history.

Normally, one cannot get away with this. But today a Pressac, waving aside historical reasoning and the mountain of documentary evidence, comes rushing forward waving some document and saying, in effect, "but how about this?", and he is respected instead of being ignored or laughed at.[675] He is credited by some with finally proving the extermination allegation as it relates to Auschwitz, although it had for years been claimed that it had been proven and that there was nothing to argue about.

Thus, to the person who objects that I have treated petty details here, which are incommensurate with the scale of the historical claim involved, I reply: you are right, but it isn't my fault! Ordinary historical reasoning observes that nobody acted, during the war, as though "extermination" was going on, and that the Jews were still there at war's end.[676] However, a lot of influential people won't accept ordinary historical reasoning, and the debate, to the extent that it exists, has revolved around the petty details.

The promoters of the legend may get away with such practices for a while in arguing the reality of physical exterminations of Jews during World War II. There are two leading reasons for this. Most obvious is the fact of the entrenched status of the legend. What ought to require proof has been allowed to flourish unproved, and the revisionists have in effect been forced to try to argue a negative. Another reason, less obvious but very simple, is that the revisionists may not be able to immediately offer correct replies to the sallies of the defenders of the legend. This appears to me to have been the case with the Topf letter. I don't believe Faurisson's immediate replies (which I would also have made) were correct. In fact, nobody could be relied on to be correct under the circumstances and in the time frame involved. A comparison: there is much building activity at Northwestern University now. Does anybody believe that, fifty years from now, perhaps after some cataclysm, anybody could reliably interpret individual documents that were records of this construction? Of course not. Nobody could do that, and nobody could infallibly interpret every Auschwitz document from the period 1941-1945. Indeed, the hypothesis I have advanced here may be wrong, even though I have had a few years to consider the solitary document in question.

Some years ago I warned of these dangers.[677] It is not out of the question that, some day, an authentic Auschwitz document might utterly confound the revisionists, i.e. raise some apparently relevant question of detail which they will be unable to answer. I can only urge that the context, that is, the massive documentation and historical circumstance supporting the revisionist position, be kept in mind in the event of such a development.

Notes

[645] | Chapter 4, p. 162, citing the Encyclopedia Britannica, 12 ed., vol. 32, (1922 - third volume supplementing the 11th edition), p. 157.
[646] | Debórah Dwork and Robert Jan van Pelt, Auschwitz, 1270 to the Present, W.W. Norton, NY, 1996, p. 219.
[647] | Booklet Zyklon for Pest Control, published by DEGESCH, apparently during the 70s. Similar information is also given in a German document that appeared at the Nuremberg trials as document NI-9912 and is presented in English translation by J.-C. Pressac, Auschwitz: Technique and Operation of the Gas Chambers, Beate Klarsfeld Foundation, NY, 1989, pp. 18-20. The reader should understand that the title of this book is misleading, as the only real "gas chambers" whose "technique and operation" are discussed are fumigation gas chambers. The homicidal gas chambers are only imagined, based on alleged "criminal traces". It is common to refer to this book in discussion of Auschwitz, because it is the greatest single published source of reproductions of original documents and photographs for the camp.
[648] | F. Puntigam, H. Breymesser and E. Bernfus, Blausäuregaskammern zur Fleckfieberabwehr, Reichsarbeitsblatt (special publication), Reichsarbeitsministerium, Berlin, 1943, p. 21. DEGESCH booklet (op. cit., pp. 7,24).
[649] | R.P. Tew, Pest Control in Germany during the period 1939-1945, H.M. Stationery Office, London, 1951, pp. 57, 96. No. 32 in the surveys of the British Intelligence Objectives Sub-Committee.
[650] | On these gas chambers, see mainly the book by F. Puntigam et al. (1943), pp. 9-68. There is also information in the aforementioned DEGESCH booklet.
[651] | Puntigam et al. (1943), p. 33.
[652] | Puntigam et al. (1943), pp. 31f, 60f.
[653] | DEGESCH booklet, op. cit., p. 25.
[654] | Pressac (1989), pp. 371, 432f.
[655] | R. Faurisson, "Auschwitz: Technique and Operation of the Gas Chambers," Journal of Historical Review, vol. 11, no. 1, Spring 1991, p. 59.
[656] | Jean-Claude Pressac, Les crématoires d'Auschwitz: la machinerie du meurtre de masse, CNRS Éditions, Paris, 1993. The document is reproduced, together with an English translation, by J.-C. Pressac and Robert-Jan Van Pelt in their article in Anatomy of the Auschwitz Death Camp, Y. Gutman and M. Berenbaum, eds., Indiana Univ. Press, Bloomington, 1994, pp. 230f.
[657] | R. Faurisson, "Jean-Claude Pressac's New Auschwitz Book," Journal of Historical Review, vol. 14, no. 1, Jan./Feb. 1994, p. 23.
[658] | Raul Hilberg, The Destruction of the European Jews, p. 571 in the 1961 Quadrangle edition; vol. 3, p. 892 in the 1985 Holmes & Meier edition. Hilberg cites a letter from the Referat to DEGESCH.
[659] | Jean-François Forges, Éduquer contre Auschwitz, ESF, Paris, 1997, p. 28.
[660] | Pressac (1989), pp. 284-287 (drawings of 23 Jan. 1942, on which Fig. 2 is based); pp. 306-312 (drawings of 19 March 1943, showing the same duct arrangement as in earlier drawings). Pressac (1989), p. 288 also reproduces a profile drawing for this arrangement; this profile drawing is also reproduced by Danuta Czech, Auschwitz Chronicle 1939-1945, Henry Holt, NY, 1990, p. 193. The "Ofen" is a cremation oven; if the reader uses a magnifying glass and squints hard, the badly lettered word "Müllverbrennungsofen" (waste incinerator) can be seen.
[661] | Pressac (1989), p. 217.
[662] | Bryan Ballantyne, "Hydrogen cyanide as a product of combustion and a factor in morbidity and mortality from fires," in Clinical and Experimental Toxicology of Cyanides, Bryan Ballantyne & Timothy C. Marrs, eds., Wright, Bristol, 1987, pp. 248-291. Yoshio Tsuchiya, "Significance of HCN generation in fire gas toxicity," Journal of Combustion Toxicology, vol. 4, August 1977, pp. 271-282.
[663] | Pressac (1989), 214, 230, 306-310, 488. Pressac and Van Pelt (1994), pp. 232f.
[664] | A.R. Urquhart, The German Rayon Industry During the Period 1939-1945, H.M. Stationery Office, London, 1952, pp. 13-16, 275. This work was no. 33 in a series of British postwar studies of intelligence objectives.
[665] | Tokio Morikawa, "Evolution of hydrogen cyanide during combustion and pyrolysis," Journal of Combustion Toxicology, vol. 5, pp. 315-330, August 1978.
[666] | Urquhart (1952), p. 272.
[667] | Robert W. Little, Flameproofing Textile Fabrics, Reinhold, NY, 1947, pp. 167-170.
[668] | Urquhart (1952), p. 272.
[669] | Urquhart (1952), pp. 15ff, 28, 150-159, 273ff.
[670] | McGraw-Hill Encyclopedia of Science and Technology, 7th edition (1992), vol. 7, pp. 139f (article on "Flameproofing").
[671] | A.R. Butz, "Some Thoughts on Pressac's Opus", Journal of Historical Review, vol. 13, no. 3, May/June 1993, pp. 23-37. Supplement 3 here.
[672] | A.R. Butz, "Context and Perspective in the 'Holocaust' Controversy", Journal of Historical Review, vol. 3, no. 4, Winter 1982, pp. 371-405. Supplement 2 here.
[673] | R. Faurisson, "Auschwitz: Facts and legend," Journal of Historical Review, vol. 16, no. 4, July-Aug. 1997, pp. 14-19.
[674] | Pressac (1989), pp. 432-457.
[675] | On Pressac's 1989 book see e.g. the NY Times, 18 Dec. 1989. On his 1993 book, which reproduced the Topf letter in question here, see (all 1993) l'Express, 23 Sept. pp. 76-87; Libération, 24 Sept. pp. 28f; Le Monde, 26-27 Sept. p. 7; Die Welt, 27 Sept. p. 1; AP report in the Denver Post, 2 Oct. p. 6A; Die Woche, 7 Oct. p. 8; NY Times, 28 Oct. p. A3 and 31 Oct. sec. 4, p. 2 and 8 Nov. p. A14; Chicago Tribune, 28 Nov. sec. 1, p. 25 and 13 Dec. sec. 5, p. 1.
[676] | Butz (1982). Supplement 2 here. For some Jewish demography see Chapters 1 and 7 herein. Much more is to be found in Walter Sanning, The Dissolution of Eastern European Jewry, IHR, 1983.
[677] | Butz (1982). Supplement 2 here.

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