The complete absence of Prussian blue staining on the interior walls of the homicidal gas chambers at Auschwitz such as the subterranean chambers of Krema II and III is in my view a direct consequence of fundamental physical chemistry chemical kinetics and the specific environmental conditions of those spaces when hydrogen cyanide gas was introduced into these chambers it contacted concrete and lime plaster containing slaked lime known chemically as calcium hydroxide through an acid base neutralisation hydrogen cyanide initially converted into calcium cyanide on the damp surface of the walls however calcium cyanide is a simple ionic salt held together purely by electrostatic forces because calcium lacks the specific electronic structure necessary to share electron density back into cyanide ions a process chemists call back-donation it cannot lock cyanide into a permanent chemical lattice also calcium cyanide is extraordinarily soluble dissolving in water at a rate of 427 grams per liter at 20C (for reference this is more soluble than table salt) rather than forming a permanent blue pigment any cyanide that initially reacted with the lime plaster in the gas chambers existed as a transient highly water soluble liquid salt film that was exceptionally vulnerable to ambient acidification and physical removal while iron cyanides like Prussian blue chemically known as iron(III) hexacyanoferrate(II) possess an extraordinary thermodynamic stability with a cumulative formation constant on the order of One hundred decillion (for reference that’s 35 zeros 100000000000000000000000000000000000) thermodynamics only determines what is chemically possible at equilibrium physical kinetics determines how fast a reaction can actually occur in the real world for prussian blue to synthesise on a wall cyanide ions must react with free dissolved ferric or ferrous iron ions in the building materials of the gas chambers iron did not exist as free ions floating in solution it was locked inside solid crystalline structural rust such as hematite or ferric hydroxide ferric hydroxide has an extraordinarily low solubility product constant of six point three times ten to the negative thirty eighth meaning it is virtually insoluble in neutral or basic water to extract even microscopic amounts of iron out of a solid rust lattice using dilute cyanide requires weeks to months of continuous contact under stable highly alkaline conditions in the gas chambers where execution cycles lasted only 20 to 30 minutes the rate of solid iron dissolution out of the plaster was effectively zero creating an insurmountable kinetic barrier that prevented Prussian blue from ever initiating its synthesis this kinetic barrier was further reinforced by the extreme biological and atmospheric acidification caused by the victims inside the chambers when hundreds of people were contained within the sealed space of a chamber human physiological stress generated massive chemical inputs into the room's atmosphere (sweat urine etc) Human respiration emits approximately 40000 PPM or 4%, carbon dioxide which rapidly dissolves into the thin surface water films on the plaster walls to form carbonic acid a chemical species with a primary acid constant p K a of 6.35 simultaneously intense physical stress produced liters of sweat containing lactic acid p K a = 3.86 alongside organic acids from bodily fluids buffering the liquid film on the masonry to a pH between 5.0 and 6.0 because hydrocyanic acid is an exceptionally weak acid with a p K a of 9.21 carbonic acid and lactic acid are hundreds to thousands of times stronger as proton donors applying the Henderson-Hasselbalch equation to the surface moisture film on the plaster reveals the dramatic impact of this biological acidification at a buffered surface pH of 5.5 over 99.98% of the dissolved cyanide in the liquid film was instantly protonated back into un ionised volatile hydrogen cyanide gas, leaving less than 0.02% as free cyanide ions because un ionised hydrogen cyanide has a low boiling point of 25.6C and a very high vapour pressure it immediately off gassed out of the surface moisture and escaped back into the air at the same time the incoming wave of carbon dioxide permanently reacted with the slaked lime in the plaster converting calcium hydroxide into insoluble calcium carbonate or limestone this process permanently exhausted the wall's surface alkalinity and destroyed its chemical capacity to absorb any further hydrogen cyanide gas (one and done) the transient calcium cyanide that had briefly formed on the plaster was thus chemically stripped and forced back into the room's air mass as a gas once surface acidification forced the cyanide out of the moisture film and back into the atmosphere as volatile hydrogen cyanide gas mechanical ventilation occurred to purge the air mass from the chamber immediately following this ventilation process the sonderkommando units entered the space and hosed down the concrete floors and plastered walls with high pressure liquid water to clean away bodily fluids because calcium cyanide is freely soluble at 427 grams per liter this hydrological washing operation instantly dissolved and flushed any remaining surface cyanide salts down the floor drainage channels within seconds the rapid off gassing of the gas into the ventilated room air combined with the water washing by the sonderkommando completely stripped cyanide from the masonry long before the slow kinetic dissolution of solid rust could supply the iron ions required to build Prussian blue these physical realities directly refute multi step mechanisms proposed in revisionists like Germar Rudolf's five step model which attempt to argue that Prussian blue should have formed Rudolf proposed a sequence involving the absorption of hydrogen cyanide its ionic splitting into cyanide ions the displacement of rust to form iron cyanides the reduction of ferric to ferrous iron and the final precipitation of Prussian blue every single step of this model would collapse under the environmental conditions of the chambers adsorption required a permanent alkaline film which was destroyed by carbon dioxide acidification ionic splitting was suppressed at pH 5.5 forcing 99.98% of the gas to off gas rust displacement was blocked by the extreme solubility barrier of iron oxide over short exposure times and water hosing by the sonderkommando flushed away the soluble intermediates in seconds furthermore the model fails due to the alkaline decomposition paradox: while step two required high alkalinity to generate cyanide ions prussian blue itself is thermodynamically unstable in alkaline environments decomposing via hydroxide attack into brown ferric hydroxide at any pH above 6.4 in fresh un carbonated plaster with a pH between 12 and 13 any trace Prussian blue that managed to form would have been instantly destroyed by the surrounding hydroxide ions while in carbonated or acidified plaster the cyanide off gassed into the air and was flushed away
This is my proposal for the lack of Prussian blue is that calcium cyanide formation and the victims themselves severely hindered the blue staining and the proposal by Rudolf is self contradictory.