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Subject: Prussian Blue: Why the Deniers are Wrong
PRUSSIAN BLUE:
Why the Holocaust Deniers are Wrong
by Brian Harmon and Mike Stein.
(c) August 1994
see copyright notice below
Since very few cyanide traces have been found in the homicidal
gas chambers of Auschwitz-Birkenau, many Holocaust deniers assert
that no one was gassed there {1,2}. They claim that if cyanide
gassing occurred in these structures, large traces of cyanide would
remain complexed with iron as a compound called prussian blue. As
proof, they point to the fact that large amounts of prussian blue
can be found in the small delousing chambers at Auschwitz; there is
even some staining on the exterior walls of these structures. By
comparison, the homicidal gas chambers have virtually no staining
and relatively weak cyanide traces. The deniers further claim that
the exterior staining on the delousing chambers proves that prussian
blue does not "weather away" even when exposed to the elements, so
that the lesser amounts of prussian blue found in the homicidal
chambers cannot be explained by weathering. Therefore, say the
deniers, the only logical explanation for the small cyanide traces in
the homicidal chambers is that cyanide was never used in them for
mass murder in the first place - the traces are merely contamination
from the delousing operations a few hundred yards away.
_The Leuchter Report_, a document written by the self-proclaimed
engineer Fred Leuchter {3}, describes the "scientific" sampling he
undertook at Auschwitz which "proves" that cyanide could not have
been used in the Kremas and Bunkers I and II, the sites in which
people were gassed. Although Leuchter misrepresented his
credentials and lied about his experience as an expert of execution
hardware, many deniers claim that the report is still scientifically
valid.
While this sounds plausible at first, when one studies the
chemistry, toxicology, and physical mechanisms involved, it becomes
clear that this reasoning is not valid. As a minor point, even
prussian blue is not eternally stable. It will "weather away" over
time, at a rate which depends heavily on the environment. Again,
however, this is really not important. The two crucial facts are
these: one, the chemical reactions that make prussian blue are very
slow, taking many hours to complete. Two, people die quickly from
cyanide, and from very small amounts. Lice and other insects, on
the other hand, require very long exposure to high concentrations.
These two factors explain why there is little prussian blue in the
extermination chambers, despite copious staining in rooms used to
delouse clothing.
This paper will compare the two uses of cyanide in Auschwitz;
both its use in delousing and in murder. The formation of prussian
blue and its solubility in water will also be discussed. We will
also examine the Leuchter Report and dissect Leuchter's methods. It
should then be clear why one expects fewer traces of cyanide in the
homicidal chambers, and also why the deniers have things exactly
backwards.
I. The Auschwitz Gas Chambers
There were seven gas chambers at Auschwitz: Kremas I - V and
Bunkers I and II. Kremas II, III, IV, and V were full time
industrial gas chambers, located on the Birkenau complex of
Auschwitz. These were destroyed by the fleeing Nazis, and none of
these are still standing -- only rubble remains {4}. Thus the
rubble and any cyanide complexes on it have been exposed to the
elements for the past forty nine years. Bunkers I and II were used
while Kremas II-V were under construction, and no trace of them
remains either. Krema I was a small gas chamber and was used only
for a short time before it was converted into an air raid shelter
by August 1944 (maybe earlier) {5}. Out of Auschwitz-Birkenau's
seven homicidal gas chambers, only Krema I exists as a complete
structure today.
The fact that all but one of the Auschwitz-Birkenau gas
chambers have been destroyed must be kept in mind. The rubble
has been exposed to weathering from the rain and wind, which could
carry away traces of cyanide by bulk flow and erosion. More
cyanide has undoubtedly been removed by dissolution, as prussian
blue is not completely insoluble in water. The delousing chambers
were not destroyed, so more traces of many cyanide compounds
should be found there.
II. The Leuchter Report: Cyanide Traces Were Found in the Gas
Chambers.
Both the Report of the Forensic Research Institute at Krakow and
the Revisionist _Leuchter Report_ found traces of cyanide in the
extermination facilities at Auschwitz {6, 7}. In _The Leuchter
Report_, from 1.9 to 6.7 mg/Kg of cyanide was found in Krema III,
1.1 to 7.9 mg/Kg in Krema I, 1.4 to 2.3 mg/Kg in Krema IV, and 1.7 -
4.4 mg/Kg in Krema V. These low numbers could have been false
artifacts of the measurement processes rather than any real signal.
To test this, Leuchter tested a sample of gasket material taken from
an unrelated building in the camp. If the cyanide traces in the
rubble of homicidal gas chambers were a false signal or if the entire
camp was contaminated with cyanide, this gasket material should give
a similar response. Instead, The gasket registered a flat zero
rating. Based on Leuchter's control sample, the cyanide detected in
the homicidal gas chambers is real. Even sites reduced to rubble
have traces of cyanide, while his unrelated gasket sample does not.
Unfortunately for Leuchter's poorly executed report, any
conclusions taken from Leuchter's data are limited by the report's
poor design. He took only two control samples: a negative control
that should generate no cyanide reading (the gasket material), and
one positive control that would generate a very high one (a sample
from a delousing room stained with prussian blue). Had he taken
more control samples from unrelated parts of the camp, he would
have some idea of what the normal cyanide levels were and compare
that to his findings. As he did not, he could not possibly
interpret his results in an intelligent fashion.
Yet another worry is the lack of detail Leuchter gave about his
sampling technique. Without such information, one cannot review
how Leuchter took samples and whether he was biased in choosing
which areas of a given building to take samples from. One must
wonder why Leuchter was so careless if he was truly a qualified
engineer.
Leuchter's conclusions are even more suspect. First, he asserts
that cyanide found in the gas chamber's remains are so close to the
instrument's detection limit (1 ppm) that they are effectively zero.
He does not provide his reasons for this conclusion. He also ignores
the baseline zero reading an unrelated sample of gasket material gave
him. If his results from the homicidal gas chambers are too low to
measure, one must wonder why his negative control did not provide a
similar result. His biggest error, however, is his assumption that
more Zyklon must be used to kill people than delouse clothing {8}:
"One would have expected higher cyanide detection in the
samples taken from the alleged [sic] gas chambers (because
of the greater amount of gassed allegedly used there)
than found in the [positive] control sample. Since the
contrary is true, one must conclude that these facilities
were not execution gas chambers, when coupled with all the
other evidence gained on inspection."
His conclusion was based on an assumption that far larger
amounts of Zyklon B were used in the gas chambers -- an assumption
he did not verify with facts. He ignored available information
about prussian blue formation, its solubility, and even the actual
operation of gas chambers at Auschwitz. His erroneous assumptions
and faulty reasoning rendered his report and his data useless.
Despite all of Leuchter's bungling, one is left with the nagging
problem of why are only minute traces of cyanide found in the rubble
of Birkenau's Kremas while much larger amounts are found in the
delousing chambers. Despite what may seem to be commonsense logic,
these minute traces are to be expected in these chambers, and are
consistent with the historical record.
We want to emphasize that cyanide traces were found in the remains
of Birkenau's extermination facilities, proving that cyanide was used
there. Therefore, any speculations about whether or not Zyklon-B
could be used for mass murder are purely academic. The traces were
there, so cyanide was most certainly used in these rooms.
III. Prussian Blue: What is it?
Prussian blue is a sparingly soluble salt made of three
molecules of iron (II) hexacyanate ion bound to four molecules of
iron (III) {9}. The complex can be formed under acidic
conditions with a solution of FeSO4 and cyanide ion:
Fe+2 + 6CN-1 ----> [Fe(CN)6]-4
4Fe+3 + 3[Fe(CN)6]-4 ----> Fe4[Fe(CN)6]3
prussian blue
Note that numbers with a + or - sign denote charge, while those
without signs are stoichiometric coefficients. The sulfate ion
cancels out, as it is not involved in the reaction. The cyanide
ion could be provided by a completely soluble salt like potassium
cyanide (KCN) or in equilibrium with the acid form (HCN). Note
that the counter ions for cyanide (K+ or H+) will drop out of the
equation as well.
Prussian blue is not very soluble, with a calculated solubility
constant of Ka = 10^-84.5 {10}. Its solubility is highly pH
dependent, and it is least soluble at a moderately acidic pH of
about 2 - 6 units. It becomes increasingly soluble above a pH of
4.0 {11}.
IV. Kinetics of Iron (II) Hexacyanate Formation.
Iron (II) hexacyanate is a precursor for prussian blue
formation, and the complex will not form without it. It forms in
a stepwise fashion, meaning that cyanide ions become complexed to
the iron one at a time:
Iron (II) Hexacyanate Formation
Fe+2 + CN-1 ---> FeCN+1
FeCN+1 + CN-1 ----> Fe(CN)2
Fe(CN)2 + CN-1 ---> [Fe(CN)3]-1
[Fe(CN)3]-1 + CN-1 -----> [Fe(CN)4]-2
[Fe(CN)4]-2 + CN-1 -----> [Fe(CN)5]-3
[Fe(CN)5]-3 + CN-1 -----> [Fe(CN)6]-4
Note that the final product of this reaction is not prussian
blue, it is merely the water soluble iron-cyanide complex that
combines with more iron to form prussian blue. This product is
absolutely required to make prussian blue.
This last step is very slow and determines the overall reaction
rate {12}. It is so slow that the reaction to produce iron (II)
hexacyanate can take upwards of 30 hours to complete when
FeSO4*7H20 and KCN are mixed together {13}. Since the production
of prussian blue depends on iron (II) hexacyanate, prussian blue
formation will be equally slow. This means that a very short time
of exposure to cyanide will not produce very much prussian blue at
all.
Relating this to the gas chambers at Auschwitz, the small
amounts of prussian blue in extermination facilities can be easily
explained. According to the testimonies of Hans Stark {14},
Auschwitz Commandant Rudolph Ho"ss {15}, and former inmate
Marie-Claude Vaillant-Couturier {16}, it would take around one
half hour to complete the gassing process and begin ventilation of
the chamber.
Based on this testimony, it would seem reasonable that very
little prussian blue would accrete on the walls of homicidal gas
chambers, given the very slow rate of formation and the very short
gassing times at Auschwitz. Thirty minutes is not enough to time
to produce much [Fe(CN)6]-4, as this reaction takes many hours.
Delousing chambers are a different matter. It takes a very long
time and a very high concentration to kill insects such as lice with
cyanide. Insects often need cyanide concentrations as high as 4600
ppm to kill, while humans need barely 300 ppm {17}. Also, the usage
manual from Zyklon's manufacturer, Degesch discusses fumigation
times of 16 hours or more, and a minimum of six hours if it is very
warm {18}. Given the higher concentrations of cyanide plus much
longer (32 times!) gassing times compared to homicidal gassings,
significant amounts of [Fe(CN)6]-4 would have time to form, thus
leading to the production of large deposits prussian blue in the
delousing chambers.
Not only was delousing a much longer process, it was done much
more often. Jean-Claude Pressac's _Technique and Operation of the
Auschwitz Gas Chambers_ compared homicidal gassings with delousing
process {19}:
"A hydrocyanic gas concentration of 0.3 g/m3 (lethal
dose) is immediately fatal for man, while in order to
destroy lice a concentration of 5 g/m3 applied for at least
two hours is necessary. If this concentration is maintained
for 6 hours, all insects are destroyed [source: Degesch].
In Birkenau, the quantity poured into the homicidal gas
chambers was forty times the lethal dose (12 g/m3) which
killed without fail one thousand people in less than five
minutes. [..] The contact time for the hydrocyanic acid with
the walls of the homicidal gas chambers never exceeded about
ten minutes per day at a temperature below 30 degrees Celsius.
In the clothing delousing gas chambers a minimum
concentration of 5 g/m3 was used during several cycles per
day, the duration of the cycle varying according to the
contact time chosen. This hydrocyanic saturation for 12 to
18 hours a day was reinforced by the heat given off by
stoves (situated in the chamber) providing a temperature of
30 degrees Celsius. The walls were impregnated with warm
hydrocyanic acid for at least 12 hours a day, which was to
bring about in situ the formation of a dye, "Prussian blue"
or potassium iron (III) hexacyanoferrate (II), whose
composition varied according to the conditions of
formation."
While the execution gas chambers used a higher concentration of
Zyklon B, the longer exposure time and heating led to the formation
of prussian blue. Pressac goes on to say that the blue color was
not visible immediately after the war, but now allows a very easy
and foolproof way to distinguish between delousing chambers that
have the blue stains, and homicidal ones which do not.
Besides the common individual's lack of knowledge of the
difference in time and concentration of cyanide between delousing
and homicide, another point the deniers count on to create
confusion is the nature of "mass gassing." It conjures up the
notion of an assembly line, people tossed into the chambers every
hour on the hour. However, this was not really the case.
Of the over one million people that are believed to have died
in Auschwitz-Birkenau, not all of these were gassed. Starvation,
overwork, and disease from the inhumane conditions may well have
killed more than gas, although the deliberate imposition of these
conditions makes it murder no less than death by bullet or cyanide
- both of which also took place.
Alter Fajnzylberg was a member of the Sonderkommando who was at
Auschwitz-Birkenau and managed to survive from the initial gassings
in Krema I through to the liberation. He testified that gassings
were normally carried out "several times a week," though at one
point in 1944, during the arrival of large numbers of Jews from
Hungary, Fajnzylberg noted that "gassings took place daily, and
even several times a day."{20} Even at that rate, however, the
total time of exposure, and thus the amount of prussian blue that
one would expect to form, is far less than the deniers are trying
to lead people to believe.
We realize that the chemistry may be difficult to follow for the
average reader. Those who deny the Holocaust count on this in their
claim that mass murder should produce more prussian blue than
delousing. However, perhaps a physical analogy common to many
people's experience may serve to bring the point home. Imagine two
white cotton handkerchiefs. One has a medium-hot iron placed on it
for four seconds, then taken away for ten seconds. This process is
repeated two hundred times. The other has a very hot iron placed on
it continuously for two minutes. The first handkerchief, touched by
the iron for a total 800 seconds, shows little if any scorching.
The second, exposed for 120 seconds, shows clear scorching. The
first handkerchief corresponds to the homicidal gas chambers - brief
exposure to low concentration of cyanide followed by time for the
effect to dissipate - while the second is an analog of the delousing
chambers, long continuous exposure to high concentration.
V. Solubility of Prussian Blue
As mentioned earlier, prussian blue is a largely insoluble salt
-- it does not dissolve readily. However, its solubility is
highly dependent on the pH of a solution that dissolves it. The
salt is least soluble under acidic conditions, and will precipitate
below a pH of about 6. Above a pH of 6, it is more soluble and
dissolves almost completely {21}. Even above a pH of 4.0, prussian
blue dissolves enough to poison the surrounding soil and ground
water with soluble iron cyanide. This means that prussian blue will
weather away, contrary to the claims of Holocaust deniers.
Would rain be of the correct pH to dissolve prussian blue? Based
upon a study of acid rain {22} in Northern Europe, the pH of
rainfall steadily drops from about 5.8 to 5.0 over a twenty year
period (1955 - 1975). An average pH level for the past fifty years
could then be very roughly estimated at 5.4 units. Given that
prussian blue begins to dissolve at a pH of 4.0, and that any
prussian blue on Krema II, III, IV, V has been exposed to this rain
for almost fifty years, it is surprising that any such traces remain
at all.
In their report on cyanide traces in the Auschwitz-Birkenau
complex, The Polish Institute for Forensic Research at Krakow
erroneously claims that prussian blue will dissolve in weak acid
{23}. While it will most certainly dissolve in strong acid (pH<0),
it is clearly less soluble at a moderately acidic pH from 2 - 4
{24}. Prussian blue is quite soluble in alkali, but even at the
relatively acidic pH of 4 (pH <7 is acidic), prussian blue will
dissolve enough to contaminate groundwater to hazardous levels {25}.
Perhaps this pH region of 4 - 7 is what they mean, as many weak
acids have pKa's in this region. Regardless of the Institute's
error, they are correct in surmising that very little, if any
traces of cyanide would be found in the homicidal gas chambers at
Auschwitz.
Besides the chemical mechanism of dissolution, prussian blue
exposed to the elements is subject to the physical mechanism of
erosion. Any compound which formed on the surface, would be liable
to break away in minute particles over time due to the physical
impact of rain and wind-blown dust. However, some of the compound
infiltrates into the porous brick, and becomes protected by its
hardness from this effect. Thus we see long-lasting stains even on
some outside surfaces of the delousing chambers - though these
surfaces too will have less prussian blue relative to what they did
fifty years ago. Still, it is important to keep in mind the main
point, namely that the overwhelming reason for the small amount of
prussian blue in the homicidal chambers is that there was too small
a concentration of cyanide allowed to react for too short a time
before the room was ventilated. Thus no significant quantity of
prussian blue could form in the first place.
VI. Summary and Conclusion
Prussian blue is a sparingly soluble salt with the chemical
formula Fe4[Fe(CN6)]3. It forms rather slowly, and is quite
insoluble at acidic pH. It will dissolve readily at pH of 6.0 or
above. Other components formed during prussian blue formation
would be soluble and be washed away almost if not completely in a
short time.
Given the very short time of cyanide exposure in the homicidal
gas chambers and that prussian blue forms very slowly, it is
unlikely that prussian blue could form there in significant
amounts. In delousing chambers, with their high concentration of
cyanide and long exposure times of many hours, significant amounts
of prussian blue would form.
As prussian blue is soluble enough to contaminate groundwater
with cyanide at a pH above 4.0, and that it is soluble above pH 6.0,
one should expect to find even fewer cyanide traces in the rubble of
Krema II, III, IV, and V after fifty years of exposure to the elements.
Rainfall can be expected to dissolve prussian blue, albeit slowly.
Taking all of these factors into account, it is very unlikely that
significant cyanide traces would be found in the rubble of Kremas
II - V.
Surprisingly, cyanide traces were actually found in the homicidal
gas chambers, which proves that HCN was used there. Since the Nazis
destroyed these facilities while leaving less incriminating structures
intact, it becomes clear that their purpose was not benign. The only
apparent discrepancy is that much more cyanide is found in rooms used
to delouse clothing. However, with a basic understanding of cyanide
chemistry and toxicology one can readily explain the scarcity of
prussian blue in the extermination gas chambers despite its prevalence
in the delousing facilities.
Appendix
i. Copyright Notice
(c) Brian Harmon and Mike Stein, 1994. This document may be
distributed freely as long as credit is given to the authors. This
text may not be modified in any way. Sources quoted in this text are
copyrighted by the original publishers or authors.
ii. Acknowledgements
We would like to thank Ken McVay, whose archives and personal
assistance have been of great help to us. Ken McVay maintains a
large archive of material on the Holocaust and various aspects of
Holocaust denial. These files can be accessed by anonymous ftp at
http://nizkor.org/ftp.cgi, and via the World Wide Web at
http://nizkor.org. [URLs updated 12/25/2005 knm]
iv. Quote From Polish Institute For Forensic Research
Here is the section from the Polish Institute that makes
reference to prussian blue dissolving in acid:
----------------------------------------------------------
INSTITUTE OF FORENSIC RESEARCH
In the name of Prof. Dr. Jan Sehn, Krakow
Division of Forensic Toxicology
Krakow, 24 Sept. 1990
Westerplatte 9 / Code 31-033
Tel. 505-44, 592-24, 287-50
Telex 0325213 eksad ...
The hydrocyanic acid (HCN) that is released from the
Zyklon B preparation is a liquid with a boiling point of
about 27 degrees Celsius. It has an acidic character, and
therefore forms compounds with metallic salts, which are
known as cyanides. The salts of alkaline metals (such as
sodium and potassium) are water soluble.
Hydrocyanic acid is a very weak acid, and accordingly
its salts dissolve easily in stronger acids. Even carbonic
acid, which is formed as a reaction of carbon dioxide with
water, will dissolve ferro-cyanide.
Stronger acids, such as sulfuric acids, easily dissolve
the cyanides. The compounds of cyanide ions with heavy
metals are longer lasting. This includes the already
mentioned Prussian blue, although this will also slowly
^^^^^^^ ^^^^^^^^ ^^^^^^^^ ^^^^^^^^^ ^^^^^^^^^
dissolve in an acidic environment.
^^^^^^^^ ^^^^^^^^^^^^ ^^^^^^^^^^^^
Therefore, one can hardly assume that traces of cyanic
compounds could still be detected in construction materials
(plaster, brick) after 45 years, after being subjected to the
weather and the elements (rain, acid oxides, especially
sulfuric and nitrogen oxides). More reliable would be the
analysis of wall plaster [samples] from closed rooms which
were not subject to weather and the elements (including acid
rain).
The discovery of hydrocyanic acid compounds in samples of
material which had been subject to the elements can only be
accidental.
----------------------------------------------------------
While prussian blue will dissolve in a somewhat acidic
environment, increasing acid makes it less soluble, contrary
to what the Polish report implies.
v. Endnotes
1) Leuchter, Fred. _The Leuchter Report: The End of a Myth_.
Samisdat Publishers, (c) 1998. p 17.
2) The Institute of Forensic Research Report is cited in The
Summer 1991 issue of the _Journal For Historical Review_
(Institute for Historical Review: Torrance, CA)
3) Leuchter, p 1.
4) Brugioni, Dino and Poirier, Robert. _The Holocaust Revisited:
A Retrospective Analysis of the Auschwitz-Birkenau
Extermination Complex_. (Washington D.C.: Central
Intelligence Agency). (c) Feb. 1979, pp 13-14
5) ibid, p 5.
6) Institute of Forensic Research Report, JHR, summer '91
7) Leuchter, p 17.
8) Leuchter, p 11.
9) Sharpe, A. G. _The Chemistry of Cyano Complexes of the
Transition Metals_. (Academic Press: New York, London, San
Francisco) (c) 1976, p 122.
10) Meeussen, Johannes C. L., Meindert Keizer G., van Riemsdijk,
Willem H., and de Haan, Frans A. M. "Dissolution Behavior of
Iron Cyanide (Prussian Blue) in Contaminated Soils"
_Environmental Science and Technology_, vol 26, no 9, 1992.
p 1834 (figure).
11) Meeussen, p 1832.
12) Sharpe, 104.
13) ibid, p 104.
14) _"The Good Old Days": The Holocaust as Seen by Its
Perpetrators and Bystanders_. ed by Ernst Klee, Willi Dressen,
and Volker Reiss. English translation of "Die Scho"ne Zeit".
(New York: The Free Press, div. of MacMillan, Inc.) (c) 1991.,
p 255.
15) _"The Good Old Days"_, p 272.
16) _Documents on the Holocaust: Selected Sources on the
Destruction of the Jews of Germany and Austria, Poland, and the
Soviet Union_. ed. by Yitzhak Arad, Yisrael Gutman, and
Abraham Margaliot. (Jerusalem: Yad Veshem) (c) 1981, p358.
17) Hansen, James D., Hara, Arnold H., Chan, Harvey T., and Tenbrik,
Victoria L. "Efficacy of Hydrogen Cyanide Fumigation as a
Treatment for Pests of Hawaiian Cut Flowers and Foliage After
Harvest" _Journal of Economic Entomology_, vol 84, no 2, p 534.
18) Nuremburg Document NI-9912, the Degesch Manual on how to use
Zyklon properly. Both German and English versions were obtained
from:
Mendelsohn, John and Detwiler, Donald S. _The Holocaust:
Selected Documents in Eighteen Volumes._ "Volume 12: The 'Final
Solution' in the Extermination Camps and the Aftermath" (New
York: Garland Publishing) c. 1982, p 137.
19) Pressac, Jean-Claude. _Auschwitz: Techniques and Operation of
the Gas Chambers_ (English edition) (New York: Beate Klarsfeld
Foundation) c. 1989, p 53.
[The translation quoted in this document is by Michael Stein, made
directly from the photographic facsimile of the original French
statement. It is slightly more literal than the translation
appearing in the English edition of Pressac.]
20) ibid., p 124-125.
21) Meeussen, p 1832, 1835.
22) Ode'n, Svante. "The Acidity Problem -- An Outline of Concepts".
_Water, Air and Soil Pollution_ vol 6, 1976. p 142.
23) Institute of Forensic Research Report, _JHR_, summer '91
24) Meeussen, p 1835.
25) ibid, p 1832.
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