It's because brick is not easily penetrated by cyanide ions, and the iron oxide in brick is not very reactive.
Now the gas chambers were made of brick, however all of the large gas chambers at Auschwitz were destroyed by the Germans at the end of the war.
The vent-less morgue roof looks exactly the same as it did in 1943, although it collapsed from the force of an explosion detonated by the Soviet Army between January 27 and February 18, 1945. Inspection at the locations of marks on the 1944 air photos showed no cement patches of previous holes, as any patches would have been visible along the straight line impressions left from the original 1943 cement forms. In 1944 this was what the inside of the ventless morgue roof looked like, before being tilted and partially collapsed from the winter 1945 explosion.
'Cyanide Chemistry at Auschwitz '
AHUGECAT wrote:The picture of the ceiling of Krema II shows a paint-like coating hanging loose in pieces. If there is no iron in the coating, the norm, it would not have stained.
astro3 wrote:This guy is trying to make up the idea that brick may not contain iron. But it does: there is 5% iron in the earth.
He is wanting to believe that the bricks were not very porous to hydrogen cyanide, however they were because: (1) the delousing chambers have blue inside and out, showing HCN penetration right through the walls, (2) Rudolf took some deep samples comparing cyanide levels at several depths just to answer this matter.
This guy is believing in the Polish survey, however I reckon that is rather fraudulent because it cites results in cyanide parts per billion in the brick (micrograms per kg) whereas no-one can measure that level. I suggest to him that it is the Leuchter and Rudolf investigations together which really show where the cyanide was used.
Quite low exposures to HCN can turn walls blue, as Rudolf showed in the case of church walls, indoors, which had been fumigated with hydrogen cyanide.
Or, maybe forget about the blue colour and just focus on cyanide levels: a 2000 differential between the mean iron-cyanide levels in the delousing chamber walls (around 5000 parts per million), versus the 2-3 parts per million found everywhere else (caused by occasional delousing).
The point here is, that the Rudolf & Leuchter measurements failed to find any significant elevation in residual wall cyanide,between the alleged human gas chamber remains, and other chambers eg bedrooms etc.
Of course Rudolf sleazes his way around this by trying to insert his own numbers in but even he cant sidestep the fact that the numbers corroborate the witness testimony, without the gas masks the workers were in negligible danger, with gas masks no danger at all.Inspection of Irmscher's paper shows (assuming the Erco carrier) that the concentration that would be present after 30 minutes, for example, would have been 20 to 40% of the total, i.e., 900-7200 ppmv. So it was only necessary to reduce the concentration in the gas chambers by a factor of 20-200 times in order for the Sonderkommando to enter even without gas masks. The remainder of the Zyklon could outgas safely in the outside atmosphere - without, needless to say, "poisoning the entire camp."
The gas chambers were 30 m long by 7 m wide: 210 sq m. They were 2.4 m high, for a volume of 504 cu m.  Those same chambers had a ventilation system with both intake and exhaust fans, capable of cycling 8000 cu m through the room each hour.  This is commonly referred to as 8000 ÷ 504 = 15.8 "air exchanges per hour."
If the initial concentration were more than seven times higher (7200 ppmv), owing to the nature of exponential math, the same concentration of under 20 ppmv would be reached in less than 23 minutes. Even if the residual Zyklon had not been removed and the chambers had the full concentration of 18,100 ppmv, the concentration would be less than 20 ppmv in 26 minutes. http://www.holocaust-history.org/auschw ... e-science/
After that, all it is is probability of which the probability of the effect occurring in the environment of a gas chamber would be low. None of the subsequent Rudolf experiments took note of this fact.The Prussian-Blue staining indeed owes its presence to exposure to HCN, but the conditions under which it formed were not universally present in all facilities exposed to HCN. The rate of Prussian-Blue formation may be very different under the conditions used in homicidal chamber [sic] versus the conditions in delousing chambers.
Experts forced Rudolf to retreat his previous claims of certainty. "[Critic] Green's second prerequisite is that I have to "demonstrate rigorously" "that the kinetics involved with the formation of such pigments dictate that significant quantities should be formed in all of the homicidal gas chambers". I stated before that this is nearly impossible. Consequently we must conclude that chemistry is not a science with the power to prove or refute human gassings in Auschwitz "rigorously"
astro3 wrote:THE STRANGE LOGIC OF RICHARD GREEN
Dr Richard Green, the Holocaust chemist, has his own Wikipedia section . His anti-Rudolf polemics on the web include The Chemistry of Auschwitz  Leuchter, Rudolf and the Iron Blues  and Rudolf, Rhetoric and Reduction . We'll here allude to these as CA, LR and RR, respectively. In these texts, weak chemical arguments alternate with strong invective. The arguments are saturated with venom, as are the delousing-chamber walls of Birkenau with cyanide. He scoffs at the practical labour and conclusions of others, himself a mere armchair theorist.
A lot of his argument is about the Iron Blue, so let's remind ourselves with a quote from Rudolf:The walls of the delousing buildings are saturated through and through with cyanide compounds, of which only a part becomes visible as iron blue, predominantly in damp areas and at the surfaces due to accumulation processes .
In addition there are very small traces of cyanide not bound to iron, mainly calcium cyanide, Ca(CN)2, water-soluble. The Polish 1991 study looked at this, and Dr Green is concerned to extol this survey, dismissing the others.
The Burden of Proof
The terminology used in Green's essay can be confusing. Thus, we find statements like: 'The burden of proof that Prussian blue must have formed under the conditions present in the gas chambers is on the deniers' [LR]. and again: '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. [LR]' Clearly, (a) Leuchter and Rudolf don't believe in the existence of any such homicidal gas chambers, and (b) no Prussian blue ever formed in such alleged chambers. Let's try one more time to follow Dr Green, here:Yet the burden of proof here lies with the deniers. They claim to prove that gassings could not have occurred in the gas chambers. To make such an argument, they need to demonstrate that their proposed mechanism of Prussian blue formation must be operative in the gas chambers under the precise conditions under which they were operated. Their task is daunting. [LR]
We ('the deniers') are affirming the simple fact that Prussian Blue never appears in the AHGCs - which Dr Green here calls 'the gas chambers' - for the simple reason that cyanide wasn't used in them; whereas, it is present in the DC walls. We are not obliged to explain any 'proposed mechanism' whereby this blue complex forms ; it suffices to point out that it does form, it is there, is permanent, and those parts of wall having it, contain high iron and cyanide levels.
Jean Pressac may have been correct, that the deep blue only matured slowly, appearing there after the War . Mother Nature was thus pointing out something, which turned out to be vitally relevant. Green correctly states, that 'Yet the burden of proof here lies with the deniers. They claim to prove that gassings could not have occurred in the gas chambers. [LR]'
We do, indeed: chemical proof, Dr Green. One needs to add a caveat that his terminology can mislead: Pressac's hard-to-find magnum opus showed diagrams of rooms labelled 'gas chambers' (gaskammers) that were clearly the delousing chambers and that is not Dr Green's meaning.
Where is the Prussian Blue located? Dr Green tells his readers, that 'Some of the delousing chambers exhibit blue-staining, whereas the homicidal gas chambers do not,' [CA, V] whereas the truth is, that all of the DC walls exhibit blue-staining while none of the AHGCs do so. The sole exceptions here are (a) the AHGC at Majdanek which has blue walls, easily explained by the fact that what is shown there was, in reality, a delousing gas chamber , and (b) the Dachau DC walls have no blue pigment, because their walls were coated with paint that was impermeable to gas and water. 
He doesn't want conclusions to be drawn from the blue hue, nor indeed from Leuchter and Rudolf's measurement of their ultra-high iron cyanide levels:The bulk of the cyanides detected by Leuchter and Rudolf were in the form of Prussian blue and/or related compounds. That there is a discrepancy between the amount of Prussian blue between some of the delousing facilities and some of the homicidal facilities is clear from inspection of the prominent blue staining on some of the delousing chambers (and the chemical work of Leuchter and Rudolf, even if honestly conducted, shows no more than is evident from inspection). The important question is whether such staining is an accurate marker for exposure to HCN. Must it always be present in buildings exposed to HCN? ... These measurements (of iron cyanide) are essentially meaningless. The information content is not more than the fact that some of the delousing chambers have blue-staining and the homicidal chambers do not. [RR]
Dr Green seeks to persuade his readers, that the contrast between the DC walls glowing with deep blue and the AHGCs which have absolutely none, is merely 'a discrepancy between the amount of Prussian blue between some of the delousing facilities and some of the homicidal facilities.' Sophistry can be carried no further! The Prussian blue has appeared, he explains, for complicated reasons, but one cannot say that it is caused by the cyanide gas of half a century ago. He then dreams up the notion that Leuchter and Rudolf measured cyanides 'in the form of Prussian blue and/or related compounds' - whereas what they measured was total cyanide. The conclusion he draws from all this, is that the Polish approach has the advantage, because it avoided the Prussian Blue issue:Cyanide residues, not in the form of Prussian blue are far more susceptible to weathering away. The IFRC researchers experimented with exposing building materials to HCN and found that the cyanides were easily removed with exposure to water. The samples that they found containing cyanides from the Kremas were carefully taken from places in the chambers that were as sheltered from the elements as possible. Leuchter and Rudolf, collecting their samples illegally, could not afford that luxury. [CA,V]
We agree that the 'cyanide residues not in the form of Prussian blue' are more susceptible to 'weathering away', which could be why Ball, Leuchter and Rudolf didn't measure them.
Blue Church Walls
The connection between fumigation with Prussic acid for de-lousing treatment and the development of Prussian blue, has been demonstrated by Rudolf's survey of the latter forming in an old church (a Protestant church of Wiesenfeld) after it received this treatment. A report found that:Several months after the building was opened to the public, small ink-blue spots appeared at various places on the newly plastered surfaces. Little attention was paid to them at first; it was assumed that they were ink stains or the like. But the spots grew larger, and in some parts of the building discolored patches up to about a square meter (10 sq.ft.) in size developed. Even after one-and-a-half years new blue discolorations still formed in some places. No-one could remove the blue and so all of the plaster had to be removed. 
Here Dr Green complains 'The fact that blue staining occurred in this church is not sufficient to demonstrate that the same mechanism is responsible for the blue staining in the delousing chambers.' Isn't it? What more does he want?  Let's listen carefully:buildings that were exposed to HCN but did not form Prussian blue stains (as Gauss's fumigation experts attest is the normal state of affairs). 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. We must therefore conclude that Prussian blue is not a good marker for exposure to hydrogen cyanide. Because of the fact that Prussian blue is much less susceptible to weather, a building that has Prussian blue stains will have a total cyanide content much greater than one in which Prussian blue did not form. Because of these facts, we must conclude that judging exposure to cyanide by means of the total cyanide content is inappropriate. A fair marker for exposure to hydrogen cyanide is to measure the remnant cyanide content when iron compounds are excluded. Such an experiment was actually performed by the Institute for Forensic Research in Cracow.? [RR]
Did you follow that? He is endeavouring to avoid the plain-as-day conclusion that massive cyanide gas infusions caused walls to turn a deep blue due to the formation of iron cyanide, which endure for half a century! He is irked by the simple force of the argument. This effect does not always happen, to be sure, and some churches have not turned blue after de-bugging with cyanide gas (a procedure still used today in Germany).
After the human gassings had taken place the walls were washed down, Dr Green explains, and this would have dissolved out all of the cyanide: this 'may actually be the explanation for the presence of Prussian blue in the delousing chambers yet its absence in the homicidal chambers.'[LR] This is an argument which might work better in reverse: if the walls were kept damp by washing them down, this would facilitate their absorption of cyanide, as compared to the dry walls of the DCs.
The polish survey (IFRC), he claims, found raised cyanide in the AHGCs as compared to 'control' samples, but not much of a difference between DC & AHGC walls:The IFRC found traces of cyanide at levels significantly above background in all 5 Kremas as well as bunker 11. They also measured concentrations in bath-house B1-A in Birkenau, which was used for delousing prisoners' clothing ... So it is true that the highest measurements were higher in fumigation chambers ... but not by much [CA].
The DC wall values ('bathhouse B1-A in Birkenau') were, as we have seen, three times higher than the AHGC walls, using the Polish approach . Measuring the iron cyanide gives at least a thousandfold difference, as three surveys have shown, whereas if, for some obscure reason, Dr Green does not want to use this, then measuring only the non-iron bonded cyanide, will give him a factor of three. Comments about 'not much' difference are here totally inadequate. Further, if he is keen on measuring soluble cyanides, as opposed to the insoluble iron cyanide complexes, can he please tell us why he believes that these are a memory of what happened sixty years ago? The iron cyanide presence is permanent - despite experts at the Zundel and Irving trials trying to scoff at Leuchter's work in this respect - but, what reason is there to assume that parts per billion of soluble cyanide hold any such memory? Scientific method should here involve starting off with the null hypothesis, that these extremely low levels of soluble cyanide in the walls merely reflect ambient conditions, eg atmospheric nitrogen somehow combining with carbon or whatever. One then has to refute this, if one is to establish that these are a record of something done to the walls in the past. Merely to say that the sample sites were 'sheltered from the elements' may not here be adequate.
Green is prone to stating that the Polish team 'took several samples from Bunker 11, and Kremas I-V. They found levels of cyanide significantly higher than background levels in all of these sites of homicidal gassing.' A concentration of 0.09 parts per million is not significantly higher than background, which as I've argued earlier the Polish team did not well ascertain (they just put it as zero parts per billion). 'Do the homicidal gas chambers contain more cyanide compounds than an ordinary barracks? The answer is yes as discussed below' [CA, III]. A more truthful answer here would be that, if the Leuchter and Rudolf data-sets are combined, they give a mean AHGC wall cyanide level somewhat elevated with respect to control levels ('ordinary barracks'), however this difference lacks statistical significance (see above, April 2nd).
As a general comment, the scientific method is used if one is not sure about an answer, and wish to be guided, by putting questions to Nature. The experiment thereby aims to test Nature, and find an answer. Dr Green, in contrast, always appears as being certain about his answers, and what he wants to believe. His essays aim to show the moral depravity of those who disagree with him, owing to their wilful pursuit of Untruth. This seems to me more a theological goal, whereby Truth is revealed (and Green quotes some not-to-be-doubted sources of What Really Happened) and an apologist like him is there to damn and dismiss doubters. If we turn to the Nizkor website (the official Polish Holocaust info site) section on Leuchter , it complains that, by taking his samples, Leuchter committed sacrilege, that he profaned and violated the sanctity of this site by his act of 'desecration.' Dr Green here appears as rather defending the sacred legend. Unperturbed, it must be our business to ensure that technical-scientific considerations are applied to this debate, and become its fulcrum, and not be derailed by such endeavours to ethically-damn persons of incorrect opinion.
This powerful debate, of interest to the entire human race, has never been published in any English-language chemistry journal!
2. 1998 http://www.holocaust-history.org/auschwitz/chemistry/
3. 1998 http://www.holocaust-history.org/auschw ... stry/blue/ , also http://veritas3.holocaust-history.org/a ... stry/blue/
4. By Green & J McCarthy, 2000: http://www.holocaust-history.org/auschw ... e-science/
5. Dissecting the Holocaust 2003 p.366, http://www.vho.org/GB/Books/dth/fndgcger.html.
6. Iron in the wall mortar is present in its trivalent form, whereas the Iron blue is present in both di- and tri- valent forms. Some form of reducing agent is therefore necessary to obtain the bi-valent iron, and Green and Rudolf debate this.
7. Truth Prevails: Demolishing Holocaust Denial 1990, Ed S. Shapiro, p.38
8. Thanks to F.P. Berg for this info. Jean Pressac (in Auschwitz: Technique and operation of the Gas Chambers, 1989, p.555) commented likewise upon this Majdanek DC, that its red-ochre bricks were stained dark blue because this 'gas chamber' had been a delousing installation; Green denied this (C of A), with an argument that solely involved scoffing at the 'deniers:' 'Happy to be logically inconsistent as long as they can spread a bit of confusion'.
9. The Rudolf Report p.152
11. Iron Blue used to appear as a by-product of city gas or 'coke gas' in Germany. It was washed with iron peroxide in order that the cyanide in would be eliminated. Iron Blue was the end-product of this, so there is Iron Blue around old German city gas works. (The Rudolf Report p.179) It is regarded as non-polluting because of its great stability.
12. Reminder: I showed that the mean cyanide levels of the Polish study were, DC wall mean 0.27 ppm (Birkenau Bath-House Camp B1-A) compared to 0.09 ppm for 5 AHGCs, that's a big difference.
astro3 wrote:Dr Green's Fallacy
Dr. Richard Green asks his readers to believe - in his usual armchair, arm-waving fashion - that the Polish method is three hundred times more exact than that used by Rudolf: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.
We get no hint that Dr Green might need to go into a laboratory to ascertain this. He starts by trying to obfuscate the accuracy achieved by others: Alpha Laboratories used by Leuchter could only achieve 1 ppm, while the Feselius Institute used by Rudolf seems to have been able to measure reliably down to 0.1 ppm - quite an achievement.
I here argue that the method used by Rudolf and that of the IFFR (Polish) actually have the same accuracy, so that Dr Green's claim, central to his entire argument, is totally bogus.
There are two relevant papers. The first is a 1947 paper by Epstein which gives the method that was used by the Polish team, Marciewicz et al. clearly allude to it as such . It measured cyanide ion by a colourimetric method. The second paper is the more modern DIN-protocol as used by Rudolf. Ask yourself, how likely is it that a 1947 method would be 300 times more accurate than the modern, German method? That's what Green is averring. As a general comment, chemists only started to be able to measure parts per billion within the last couple of decades. For example, EU mandates for pollutants and pesticides are liable to cite such low levels. But, prior to, say, 1980, you would be hard-pressed to find a chemist who would claim to be able to measure anything much down much below one part per million.
The 1947 paper by Epstein makes it quite clear, that his method only goes down to 0.2 parts per million. Or, fairly clear: it says, e.g., 'One millilitre of the solution containing up to 1.2 micrograms of cyanide ion is treated in the manner described above.' That's 1.2 parts per million; and again, 'As little as 0.2 micrograms of cyanide can be estimated ... ' and that is in one ml of solution, i.e the lower limit of detection. At last! We are clearing up the deep, deep confusion - inexcusably perpetrated by Jan Markiewicz et al in their 1994 paper. One is startled that in the (fairly respectful) debate that went back and forth between them and Rudolf, no-one seemed to realise this.
It seems to me, that this throws doubt upon the endeavour of the Polish team, with their false claim to have measured down to 2-3 micrograms of soluble cyanide, per kg of brick - which Dr Green fell for. One is surprised that he was so gullible. Let's quote the untrue and persuasive-sounding words, from the Polish report:In various posts above I expressed scepticism over that, but now, having finally checked out the original paper, I'm more categorical! However many years one uses a colorimetric method, ie measuring the intensity of a colour (which is logarithmically related to the concentration), it will never go down to anywhere near that accuracy.Having applied this method for many years, we have opportunities to find its high sensitivity, specificity and precision. Under present circumstances we established the lower limit of determinability of cyanide ions at a level of 3-4 ,ug CN- in 1 kg of the sample.
The DIN Protocols
There are special laboratories that perform Deutsches Institut fur Normung (DIN) standard analyses. These are inspected, to make sure they are following the protocols adequately. I was able to read a copy of the cyanide-method used by Rudolf in English translation, from the British Standards Institute, and its called DIN 38-405, 13 . Its very expensive, 105 Euros for a mere dozen web-downloaded pages! I was allowed just a few of its pages photocopied. This is the best, modern method - people wouldn't pay all that and have the high-standard labs required, if there were some better method available, elsewhere. There is no better method.
I summoned up my courage, and strode into my university's chemistry department, brandishing the DIN protocol. As good fortune would have it, I got chatting to a chemist, who had his elbow resting on a large book of inorganic chemical analysis - a reassuring sight. He was intrigued by the idea of cyanide wall-measurements, and he explained to me about DIN. It described two different types of cyanide that were to be measured in any sample, the one total cyanide, and the other 'readily liberable cyanide' - these two correspond to the two methods we have been examining, viz the Leuchter/Rudolf versus the Polish . He explained how one must not pour cyanide residues down the sink because quite weak acids will dissociate the salts and liberate cyanide. The readily-liberatable cyanide was defined by DIN as, that which produced the gas at room temperature, with an air current and a pH of 4, i.e., weakly acidic. This worked for salts of sodium, potassium, magnesium etc., whereas the complex iron-bonded cyanide (Prussian Blue) only dissociates on boiling with hydrochloric acid (in the presence of dissolved copper) . Those are the two methods.
They are both assigned the same exactitude, the same level of accuracy, by the DIN protocol. The threshold of detection applies for the final solution of cyanide, after it is liberated from the original sample, and then re-dissolved in sodium hydroxide solution. Starting with a few grams of wall, one could easily end up with a few hundred ccs of solution in which the cyanide is dissolved. Thus, if the limit of accuracy is given as 0.01 ppm or 10 ppb , then this could imply a limit of accuracy of 1 ppm for the brick sample. This, a major problem as regards accuracy, is the same for both methods.
For an up-to-date discussion, one should consult http://www.cyantists.com/analysis.html , which explains the different classifications of cyanide, which are: (1) total cyanide; (2) weak acid dissociable cyanide; and (3) free cyanide.
1. http://www.holocaust-history.org/auschw ... stry/iffr/ Green 'A study of the Cyanide Compound Content in the Walls of the Gas Chambers in the Former Auschwitz and Birkenau Concentration Camps,' in John C. Zimmerman, Holocaust Denial: Demographics, Testimonies and Ideologies, U.P.Amer., 2000, pp.259-262.
2. Joseph Epstein, 'Estimation of Microquantities of Cyanide' Analytical Chemistry 1947, 19, 272-4.
3. http://www.nizkor.org/ftp.cgi/orgs/poli ... ter.report
4. Order a copy from http://www.mybeuth.de.
6. DIN's definition of readily liberable cyanide: 'cyanide of hydrogen and all compounds containing cyanogen groups which split off cyanide at room temperature and at a pH of 4.'
6. The non-complex iron compound, hexacyano-ferrate Fe(CN)6 is soluble, he explained.
7. This DIN procedure will work in solutions 'containing more than 0.05 mg/l cyanide ions,' at which threshold level it is repeatable within about 10%.
astro3 wrote:ADVICE FROM A CYANIDE EXPERT
The official, pro-Holocaust chemical argument, as put forward by Dr Richard Green, has to a large extent disintegrated, because (a) the Polish method of analysis was not reliable down to the low levels claimed, and (b) it does not convey a reliable memory of bygone decades. I have written to Dr Green advising him of these problems with his argument.
The ‘cyantist’ website (http://www.cyantists.com) offers advice concerning the measurement of cyanide and I found that one of the experts there commented helpfully on the dilemmas here examined. Thus, what follows is from a top expert on the subject! I doubt he will mind me quoting from his replies. What the Polish survey measured is here called ‘weak-acid dissociable’ (WAD), i.e. cyanide that is readily liberated by weak acid. First, his general comment:He is clearly not approving of the Polish method in the context of Auschwitz walls.There are three basic forms of cyanide, free, weak acid dissociable (WAD), and total cyanide. Total cyanide measures all forms including iron cyanide (Prussian blue), the weakly bound metal cyanide complexes such as copper, nickel, and zinc, and free cyanide which is HCN and CN-. The weak acid dissociable cyanides or WAD cyanides which are the weakly bound metal complexes is equivalent to the German [i.e. as described by the DIN protocol] readily liberated cyanide, also known as easily liberated or available cyanide. It seems very unlikely if the German procedure was used that any cyanide would have been found as these cyanide forms are not persistent over time certainly fifty years. The Polish researchers should have used the total cyanide method which measures not only the WAD forms or readily liberated but also iron cyanide the most likely form in the event the cyanide interacted with brick material which likely contained iron [it had 1% iron]. This form is stable chemically and breaks down only rapidly in the presence of light. So to answer your question the iron cyanide compounds (Fe(CN6)) would only show up if the total cyanide analysis was used. The methods I am referring to are found in Standard Methods. So in other words the Polish researchers did not use analytical procedure I would have used in this investigation.
One is startled that the accuracy of the methods seem not to have improved, in recent years:He is here NOT crediting the Polish data, endlessly repeated by Dr Green and various other pro-holocaust authors, which has parts per billion background levels, and the threshold he quotes is that of the DIN protocol. The latter is dated 1981, and I was shown on a visit to the British Standards Institute (at Ealing, in London) an online draft of the new version expected next year: it still had the same limits of accuracy, unchanged!. Concerning the Cyantist's comment on how the limit has to be ‘back calculated on the amount of solid originally crushed,’ let’s recall that the 0.05 ppm DIN threshold is for the solution to be measured, and this will give a rather higher limit for the original brickwork, ie it is not evident that one can attain that 50 ppb limit for the brickwork.The methods for cyanide analysis have not evolved for many years and since they are based on colorimetric analysis which is an indirect measurement it is subject to many interferences at low levels. The method can be extended for solutions down to about 0.05 mg/L which could be translated into a solid ppm value back calculated on the amount of solid originally crushed and placed in the distillation flask. Nonetheless, a very low level of cyanide could be identified. .. Reported values in the single digit ppb range are more than likely interferences and not real values as the method is subject to considerable error at this level. It is also important that a very reliable laboratory conduct the analyses one that routinely does these analyses.
Here’s a further comment from him upon the need to measure total cyanide, ie mainly iron-bound, suggesting that we cannot aspire to any further accuracy beyond that attained by the Fresenius Institute for Rudolf around 1990:If cyanide is present at all after a half a century it would be bound in its iron form which is reasonably stable in the absence of light for decades. This of course assumes, the hydrogen cyanide in the air could penetrate and combine with metals in the brick. Of course collecting a representative sample for analysis is critical. Assuming a representative sample could be collected, the proper method would be to crush the material to a small mesh size and subject it to a total cyanide analysis using the traditional full flask distillation method followed by colorimetric finish as specified in Standard Methods for the Analysis of Water and Wastewater. If it was present it may be measurable down to a range of 0.10-1.0 ppm but very unlikely any lower.
He advised me of a US institute which was the best for cyanide measurement and which would analyse samples sent. We're now in a good position to advocate further sampling of a relatively few wall samples taken from Birkenau and Auschwitz and have them analysed both for total and ‘WAD’ (easily-liberated) cyanide to compare them.