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| Discovered on googling (nitric acid stains clothes). Click to enlarge. OK, it's a bit small. What it says is "Spilled some dilute nitric acid on my clothes in chem lab, is there any way to get the yellow stain out?" |
R-NO2 + 6[H] -> R-NH2 + 2H2O
REAL INTRODUCTION
One of the curious features of the Shroud is the exceedingly weak contrast between the body image and the background. It's said one has to stand 3 or 4 metres away to discern the image...
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| Shroud of Turin (from the Turin custodians' own site) |
The image colour appears to be an intensification of the background colour, rather than a distinct colour in its own right. This has led to comments like "image formation is the result of accelerated ageing of the cloth". It's easy to say, but is it true, and if it were, what possible mechanism could be operating to make an image behave in that manner?
Then there's the logistics that any medieval forger had to address in order to pass off a 14th century length of linen as 1st century. Surely the cloth would have to be artificially aged, but how? If one knew how, then it might be possible to conceive of an imaging system that accelerated in the body image area the chemistry of what was happening in the larger non-image area.
It was a problem that Luigi Garlaschelli addressed in his modelling of the TS image by capturing and imprinting images off live volunteers by powder frottage and variants thereof. He pre-roasted linen in a heated oven and there was additional roasting later after application of powder (or slurry). Straightaway one can see how "accelerated ageing" becomes possible in a forgery scenario. Conceiving of a mechanism is a pro-authenticity scenario is another rmatter.
G.Fazio is another author who makes frequent references to the development of colour in background as well as image, with "latency" and "stochastic imaging" being referred to constantly (though I suspect I am not the only one to wish that he would enlarge some more on precisely what he thinks is happening on a physical, chemical and biological level).
More recently, the Dutch sindonological scholar and pro-authenticist Adrie van der Hoeven has devoted a vast open-access paper - some 260 pages no less- to the question of the Shroud blood that is "too red". Her solution? She proposes that the cloth had been impregnated before use with an extract of a yellowish dye (madder), and that blood subsequently mordanted to that dye to produce the permanent colour we see today, 2000 years later (in her view). There is much about that paper and its claims I find interesting and perplexing at the same time, despite (or because of) the wealth of documentation. I only mention it here as yet one more instance in which there has been a focus not only on the image characteristics, but on the phenomenon of a 'pre-conditioned' background for that image. I'll be returning to Adrie's paper again, probably in the third posting in this 'nitric acid' series.
So the question of dual colour, maybe of the same provenance but occurring at different rates, or maybe something more complex (two different mechanisms that just happen to look the same) cannot be avoided.
I propose to address it in two parts, using my new model (see posting immediately previous to this one) - namely the HNO3 (and NOx) fumigation model, and to address background colour first, then image colour, and see if linkage between the two, albeit at different rates OR extents, can be rationalized.
Let's take the Garlaschelli model as our starting point. Heating linen in air to get a discoloration almost certainly involves oxidation. What's more, infrared and other spectral analysis of Shroud image AND non-image areas has detected the kind of functional groups that are consistent with oxidation, namely carbonyl functions ( ) etc,
But is atmospheric oxidation the only means of oxidizing organic compounds?
Answer: most definitely no. The common mineral acid studies in the last but one posting - sulphuric acid - is an oxidizing as well as dehydrating agent - but only when its close to its maximum concentration (98%) and HOT. But there's another common mineral acid, namely nitric, HNO3, which is oxidizing over a much wider range of concentration, and which importantly can act at low temperatures too, albeit more slowly that hot. As the previous post relates. nitric acid was known as early as the 13th century in Europe. What's more, it was first prepared in vapour form, albeit contaminated with oxides of nitrogen, by heating a particular mixture of solid mineral salts (nitrates and sulphates) at high temperature. Might the fumes from that reaction have been used to artificially age linen as a first step in faking a 'relic' without even bothering to condense the fumes as recoverable liquid ("concentrated nitric acid" + NOx contaminants).
I propose that the linen was suspended horizontally in a pit (probably) over a retort that was generating fumes from the aforementioned reaction mixture. It was withdrawn when the linen was judged the right aged-look colour. (The body image - next posting- may or may not have been exposed to the fumes at the sane time).
So what's the chemistry? Oxidation of sensitive carbohydrates, especially the more superficial ones of the PCW, could account for the background colour. We'll deal with the spectral analysis later (a tricky area, one I'm not looking forward to, but the nettle will have to be grasped). However, there's a second way that nitric acid can operate, especially when it's concentrated and/or relatively water-free in the vapour state - namely by nitration of protein, notably of aromatic amino acid side groups. Tyrosine is the one that dominates the literature, but tryptophan and phenylalanine occasionally figure too.
Here's a schematic diagram of the end-result of nitration (e.g. substitution of NO2 for H) of tyrosine in a protein.
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| Nitrated tyrosine side group in a protein - colour coded |
There are two systems where protein nitration occurs to make a yellow colour - one wll known, one less so, except to clinical biochemists.
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| Concentrated nitric acid acid quickly does this to unprotected skin. It looks like a burn, but is in fact a xanthoproteic reaction to produce nitrotyrosine and other nitrated proteins that are bright yellow in colour. |
The other, which I merely flag up at this stage, is the modern focus on nitrotyrosine as a marker for the overproduction of active oxygen and nitrogen species in a range of disease conditions. on which there is a growing literature. In brief, the gas nitric oxide, NO, is an important regulator in our body tissue. affecting for example the tone of smooth muscle in our arteries and thus blood pressure. However, an excess of NO can react with the active oxygen species superoxide, O2-, to form the peroxynitrite , ONO2-, which can then attack a number of sites including the tyrosine residues of proteins, forming the same nitrated entity that caused the yellow skin in the above photograph. Should my current hypothesis ever find traction (these are early days) be prepared for some pro-authenticists to seize upon in vivo nitration as a marker for what I call crucifictional physiology, comparable to Adler's outrageous ideas on 'trauma bilirubin', mere airy-fairy speculation that far too many, the STERA president included, tout as if established fact.
Enough of the chemistry. Let's look at more practical details of what's being proposed. Might the Shroud linen have been fumigated before acquiring the body image in order to give it an aged look? If so, how would that have been achieved in practice to ensure an even coloration, with no tell-tale defects that would arouse suspicions? Let's imagine that a pit was dug into the ground, into which NOx and nitric acid fumes were led from a chemical retort, and that a pole had been placed or inserted over the top on which to peg or drape over the linen (later covered with a lid of some kin or large sheet (or sheets) of glass through which to check on progress. There's a problem. Pegs, if used, would have protected part of the linen, leaving pale areas that look like 'negatives' of the pegs. If draped over, there would also be a contact zone that was protected from the fumes.Might we perhaps have a novel explanation for the Shroud's mysterious so-called 'side-strip', or 'selvedge' as referred to by Adrie van der Hoeven. It's just visible in the photo at the top of this posting as a faint line extending horizontally from the corners of the cut-out portions of the fabric, some 8cm across its small dimension. It's in fact a seam that can be unpicked. Importantly, it's the same fabric both sides of the seam.
Anyone who's anyone in Shroudology has pondered on that side strip and offered opinions, and there's no time to discuss them all. Let's take just two of them. First, there was Bernard Power's. He thought the Shroud linen's width was too wide for the slab on which the body of the crucified Jesus lay in its rock tomb, so part of it draped vertically over the side facing the viewer. He proposed that an 8cm wide strip was removed from the edge of the long dimension (i.e. 4.4m x8cm) and then sewn back onto the opposite side.
Adrie rejects that explanation, claiming that the continuity of weave both sides of the seam is too good for Power's scenario to be true. She claims the strip was cut off, then immediately re-attached by stitching. Why would anyone do that? Her explanation? What we called the Shroud linen was originally intended to be a garment, and 1st century Jewish/Pharisaic law required that garment cloth had at least one seam.
I have a rather more mundane explanation, which can be accommodated to Power's side-to-side switch OR to Adrie's in situ detachment/re-attachment. Let's suppose the Shroud linen had been pegged out and fumigated, and then the unsightly peg marks discovered. Solution: cut off and discard the border with the peg marks, and replace with the same width cut from the opposite side. How will one explain away the seam? We'll come to that in a minute.
In the Adrie scenario, the problem of peg marks was foreseen. How can one suspend the linen in fumes to get even coloration without peg marks (or pole-marks)? Answer. Cut a strip off the edge, then re-attach loosely by lengths of strong thread, and use those threads to support the linen - main section and strip - during fumigation. Later, the bridging threads are removed and the strip re-attached.
How to explain the border with the seam? The Lirey Pilgrim's badge, circa 1357, issued to commemorate the first undisputed exposition of the Shroud in a tiny French hamlet provides the answer, It is being held out vertically for display by hands that can an be seen gripping the edge. The owners of those hands are missing, due to that part of the badge being missing, but the Machy mould for a second Lirey badge shows the hands are those of men in clerical attire. It would have been an easy matter to explain why there should be a segregated part of the Shroud set aside for gripping manually, citing reasons to do with this or that practical consideration for safe or respectful handling of an allegedly 1300 year old burial shroud.
There;s another practical aspect that needs addressing: the suitability of using a strong oxidising acid and its precursors (NOx) to age linen. Wouldn't that damage the fabric, making it later prone to disintegrate, comparable to the effect that evaporating sulphuric acid had on linen (not cotton) in my recent experimentation (see last but one posting)?
There's a big difference between sulphuric and nitric acids. Soak linen in dilute sulphuric acid, and will still look wet days later, and indeed is wet, as can be confirmed by touching (then quickly rinse off with runnin g water). Why is that? It's because dilute sulphuric acid becomes more concentrated on evaporation, due to evaporation of water, while the relatively involatile H2SO4 stays behind. That is far less likely to happen with nitric acid - HNO3 being more volatile (prone to evaporate) than H2SO4.
Boiling points: nitric acid: 83 C. Sulphuric acid: 337 C.
Even pure sulphuric acid has a vapour pressure of less than 0.001 torr at 25 °C and 1 torr at 145.8 °C. (That's tiny, considering that a torr is a unit of pressure equivalent to just 1 mm of mercury in a barometer. Typical atmospheric pressure is a whopping 760mm mercury).
Even pure sulphuric acid has a vapour pressure of less than 0.001 torr at 25 °C and 1 torr at 145.8 °C. (That's tiny, considering that a torr is a unit of pressure equivalent to just 1 mm of mercury in a barometer. Typical atmospheric pressure is a whopping 760mm mercury).
Even if there were traces of HNO3 left in the cloth days or weeks after fumigation, there are chemical mechanisms too that remove it. HNO3 is prone to decompose, not only when heated but when exposed to light. It breaks down to gaseous end-products that can escape:
4HNO3 (liquid) -> 4NO2 (gas) + O2 (gas) + 2H2O(liquid)
(Terms in brackets indicate physical states at normal temperature and pressure).
As the above process occurs the acidity will gradually decrease. But in any case, the ageing process on fumigation would have been closely monitored to achieve minimal discoloration only . That would have limited the amount of unreacted nitric acid left in the fibres of the cloth. It's not inconceivable either that the treated cloth would have been treated with an agent or treatment known to neutralize and decontaminate acid, e.g. a light dusting with chalk. (There we have, in passing, an alternative explanation for the allegedly high levels of calcium on the TS).
OK, that's do for now. The next posting(s) will be asking if and how the body image could have been imprinted using HNO3/NOx chemical technology as well, either subsequent to pre-ageing of linen, or even simultaneously. At some stage the known visible and infrared reflectance spectra of the TS image and background will need to be matched against available literature values (limited!) for yellow nitrated tyrosine and other aromatic amino acids in proteins. We'll then need to consider what the target proteins are or were.
Here's a screen shot preview for starters (the full version is behind a paywall). It's the infrared absorbance spectrum of free nitrotyrosine (in acid) versus tyrosine. Click to enlarge.
Personal credo of this retired science bod: we scientists exist primarily to propose plausible and testable hypotheses. I offer that as a plausible hypothesis, as indeed I offer my novel but as yet untested nitric acid/NOx fumigation model of the Turin Shroud. It may or may not stand up to testing. If it doesn't, I'll simply abandon it, and try to think of something else. Anything's better than simply resorting to "Oh, it had to be supernatural". My beef is not with the supernatural as such. It's with those who use pseudo-science to push their agendas (any agendas), or who simply have lazy minds, or who despise scientific curiosity (or "meddling")...
Finally, there have been many false dawns for this blogger since beginning his Shroud project at the tail end of 2011 (some 250 postings to date, here and on his main specialist Shroud site. In fact there have been so many false dawns that he's occasionally felt the need to install motion sensor night lights in his head simply to see where he's going 24/7, if only to avoid bumping into solid fixtures and fittings in the all-pervading gloom. Maybe the HNO3/NOx hypothesis will turn out to be yet another false dawn, like thermostencilling, thermal contact imprinting, Maillard-assisted imprinting, alum-mordant -assisted imprinting etc etc.
But kindly note one thing, .Joe Marino: he has not yet reached a dead end, as you so engagingly put it. There are always new avenues to explore, and NO - (that's NO the negative, not nitric oxide) invoking the supernatural is not one of them. Now that's what I call a dead end, at least in experimental/scientific terms. One shouldn't need to remind him of that.
Update, Tuesday 7th April
Response so far to the new thinking? Absolutely none, despite posting the following to the shroudstory site two days ago. Yes - a complete silence reigns. It's eery!
April 5, 2015 at 8:42 am
The timing is unfortunate (this being Easter Sunday). However,
having spent 3 years in attempting to suss out the peculiar TS image,
and been told by fellow scientists (well, some at any rate) that it has
to be “supernatural” I can scarcely contain my growing conviction that a
solution is finally within reach. A hint was provided in the previous
comment or two. The question is: how to communicate the new idea? A fait accompli set out point by point? Sorry, not my style. I don’t do fait accompli
Science works by hypothesis, experiment, interpretation, modification
of hypothesis etc etc. There’s no room there for springing a fait accompli
on folk. Better to build the story in easy instalments, ones that
address the many disparate peculiarities of the TS image that have to be
accounted for. (The new “hunch” could of course be wrong, and quickly
demonstrated to be so, given it is capable of immediate testing by
existing means were there free access to the Shroud. But there’s not,
and indeed this blogger/retired biomedical scientist is not even able to
wander into that Turin Cathedral simply to see the TS with his own
eyes, so feels it’s not a huge and shameless imposition on folk,
certainly on this ‘cutting edge’ site to say what’s in his mind, and to
do so sooner rather than later.
There are two ways I can lift the lid on the new thinking. One is to post on my own site, and (no disrespect to Dan) hope it gets reported here with no details neglected or glossed over – detail being crucial in scientific research. The alternative is to drip-feed the new model here as a series of comments, as a continuation of this particular thread (why not, since Dan’s posting links to my site?) and not bother composing a posting to my own site until the feedback here has appeared. Might that not be a more internet-friendly and democratic way of doing things, while admittedly a far cry from the traditional route via peer-reviewed publication in journal articles (abstract only, cough up $$$ to get behind the paywall). What do folk think? Fait accompli on my site, or drip feed to this one?
Title for the new idea? How about: “A novel NOx/protein fumigation model for the Turin Shroud.” NOx represents the binary mix of nitrogen oxides (NO and NO2) that react together with water and oxygen to form nitrous and nitric acids (HNO2 and HNO3 respectively), or alternatively are generated in a reverse reaction when preformed HNO3 from a reaction mixture in a distillation flask dissociates at high temperature. Nitric acid reacts quickly with proteins that contain aromatic side chains (tyrosine, tryptophan etc) to form yellow ‘xanthoproteic’ reaction products. Both light sepia TS non-image background or darker, more intense TS image could be xanthoproteic reaction products formed by NOx fumigation of intrinsic linen OR extrinsic non-linen protein, or both. Several boxes can be ticked (e.g. lack of image fluorescence, even the Shroud’s mysterious side strip).
Comments invited re the best strategy for reporting a distinctly new angle on the TS body image – blood will have to wait until later. Happy Easter.
Further thought- 7pm Tuesday
Some might consider, with some justification, that too many eggs are being placed in the one basket. What if the spectral characteristics of the image and/or background do not fit with nitrotyrosine, or any other 'nitrated' entity? Does that mean having to abandon completely the nitric fumigation model (which has quite a lot going for it in general terms, as far as producing a 'ghostly' image is concerned). In fact there's at least one other chemical system/interaction that could deploy nitric acid, but which does not require protein or any other 'nitratable organic compounds. It uses green vitriol, known to medieval alchemists, and indeed conjectured to be the source of the first sulphuric acid. Green vitriol is known today as iron (II) sulphate heptahydrate, i.e. FeSO4.7H2O, and I already have a large bag of it in the garage (it's cheap to buy as moss killer for lawns) and in fact used it 3 postings back to test out Joe Accetta's ideas re ink imprinting (the iron forms an intense black solution when added to extracts of plants tannins, like boiled/sieved pomegranate rind in my experiments - a substitute for medieval oak galls). Nitric acid turns green iron(II)sulphate brown. It's a simple oxidation of iron(II) to iron (III), or ferrous to ferric in the older system of chemical nomenclature. It might be possible to devise an imprinting medium based on iron(II) sulphate that is then "developed" by exposure to nitric acid fumes until the desired colour is achieved. Admittedly one would then have to find a way to remove the unreacted iron (II) while leaving the iron(III) in the fibres of the cloth, but that's not impossible (washing etc).
There are two ways I can lift the lid on the new thinking. One is to post on my own site, and (no disrespect to Dan) hope it gets reported here with no details neglected or glossed over – detail being crucial in scientific research. The alternative is to drip-feed the new model here as a series of comments, as a continuation of this particular thread (why not, since Dan’s posting links to my site?) and not bother composing a posting to my own site until the feedback here has appeared. Might that not be a more internet-friendly and democratic way of doing things, while admittedly a far cry from the traditional route via peer-reviewed publication in journal articles (abstract only, cough up $$$ to get behind the paywall). What do folk think? Fait accompli on my site, or drip feed to this one?
Title for the new idea? How about: “A novel NOx/protein fumigation model for the Turin Shroud.” NOx represents the binary mix of nitrogen oxides (NO and NO2) that react together with water and oxygen to form nitrous and nitric acids (HNO2 and HNO3 respectively), or alternatively are generated in a reverse reaction when preformed HNO3 from a reaction mixture in a distillation flask dissociates at high temperature. Nitric acid reacts quickly with proteins that contain aromatic side chains (tyrosine, tryptophan etc) to form yellow ‘xanthoproteic’ reaction products. Both light sepia TS non-image background or darker, more intense TS image could be xanthoproteic reaction products formed by NOx fumigation of intrinsic linen OR extrinsic non-linen protein, or both. Several boxes can be ticked (e.g. lack of image fluorescence, even the Shroud’s mysterious side strip).
Comments invited re the best strategy for reporting a distinctly new angle on the TS body image – blood will have to wait until later. Happy Easter.
Further thought- 7pm Tuesday
Some might consider, with some justification, that too many eggs are being placed in the one basket. What if the spectral characteristics of the image and/or background do not fit with nitrotyrosine, or any other 'nitrated' entity? Does that mean having to abandon completely the nitric fumigation model (which has quite a lot going for it in general terms, as far as producing a 'ghostly' image is concerned). In fact there's at least one other chemical system/interaction that could deploy nitric acid, but which does not require protein or any other 'nitratable organic compounds. It uses green vitriol, known to medieval alchemists, and indeed conjectured to be the source of the first sulphuric acid. Green vitriol is known today as iron (II) sulphate heptahydrate, i.e. FeSO4.7H2O, and I already have a large bag of it in the garage (it's cheap to buy as moss killer for lawns) and in fact used it 3 postings back to test out Joe Accetta's ideas re ink imprinting (the iron forms an intense black solution when added to extracts of plants tannins, like boiled/sieved pomegranate rind in my experiments - a substitute for medieval oak galls). Nitric acid turns green iron(II)sulphate brown. It's a simple oxidation of iron(II) to iron (III), or ferrous to ferric in the older system of chemical nomenclature. It might be possible to devise an imprinting medium based on iron(II) sulphate that is then "developed" by exposure to nitric acid fumes until the desired colour is achieved. Admittedly one would then have to find a way to remove the unreacted iron (II) while leaving the iron(III) in the fibres of the cloth, but that's not impossible (washing etc).
Later still, 8:20pm This posting with a video clip (which I'll view later) has just appeared on shroud story.com. It's a puff for Professor Fanti of Padua University and his claim, based on (dubious) chemical alternatives to radiocarbon dating, that the TS is much older than its apparent C-14 content would indicate. His new date range? It centres on 33BC +/- a few centuries either side. Well well.
But there's a snag, if one assumes for the sake of argument that my model is correct. Exposure to nitric acid fumes would wreck all his chemical clocks that rely on natural oxidation and ageing. That's especially true of the test, one of 3 as I recall, that measures fibre mechanical strength. Two seconds of exposure to fumes might do more oxidative damage than two centuries exposure to atmospheric oxygen! One could go further and say that the assumed correctness of the radiocarbon dating (1260-1390) and the evidence for 'super-aged' fibres is supportive evidence for a manufacturing process that employed a powerful chemical oxidant. Sorry Prof Fanti. You win some, you lose some, as every scientist knows only too well.
10:00 pm One thing I've been keeping on the back burner while writing this and recent blogs is a hunch I acquired about a year ago as to the way the Shroud was supposed to be interpreted by the first cohorts of pilgrims arriving at Lirey. No, it was not meant to be seen as a "painting", as suggested by Charles Freeman, and certainly not executed as such. It was meant to be seen as a bodily IMPRINT (thus the negative light/dark reversed character) and, more specifically as a SWEAT imprint acquired when the NEWLY crucified Jesus was transferred from cross to Joseph of Arimathea's linen., the latter serving as a kind of makeshift stretcher or body bag or transport. Here's a link to a late Nov 2014 posting, just one of many on the sweat imprint idea:.
In other words, our medieval artisan set out to SIMULATE a sweat (and blood) imprint, and did so using the most up-to-date chemical, or rather alchemical knowledge available at that time, say late 13th to early 14th century. Tomorrow's post will flag up out some ideas about how that may have been done, using nitric acid fumes as a "chemical developer" for the artificial sweat to create what might be termed a 'chemograph', fumes that may have chemically modified the blood at the same time to account for its odd character ("too red" etc).
Who might have had both the alchemical technology AND the audacity to produce a fake relic that still holds millions in thrall to this very day? The answer I believe is obvious. See the posting that precedes this one. The Shroud was I suggest the work of the Franciscan monk Paul of Taranto, the same man as the one previously described as Pseudo-Geber according to some modern scholars. It was made possible by Paul's technology for generating nitric acid either as fumes or condensed liquid. Whilst I've so far been able to find next to nothing about Paul the man, or even his birth and death dates, there's plenty on his philosophy and world view, and some of it looks very, very interesting. Expect a posting at some stage that puts together these hunches, together with further findings for or against the hypothesis.
Update: Wed 8th April
Have just responded to Max Patrick Hamon on shroudstory.com with this:
Max patrick Hamon
April 8, 2015 at 4:41 am
Is it for convenience’s (or gross approximation’s) sake too you keep asserting a medieval super-genius
forged the TS image?
forged the TS image?
April 8, 2015 at 5:09 am
In fact there is a possible candidate for that ‘medieval genius’
. Max, provided you accept an alchemist with a sideline in deep
philosophical discourse. I refer to the 13th century (pseudo) Geber.
Geber, who in his day was regarded as an alchemist, and thus viewed with deep disapproval by the Church, had used Geber as a pen name (it’s complicated, being an attempt it would appear to pose posthumously as an much earlier Arab alchemist). However, a strong case has been made for identifying the pseudo-Geber as the Franciscan monk, Paul of Taranto.
Geber/Paul are credited with the first clear recipe for generating nitric acid and accompanying oxides of nitrogen by calcining a mixture of metal nitrates and sulphates, initially in the form of fumes from the reaction vessel. I am coming round to the view that those fumes could have been used to produce the image we see on the Shroud – as oxidation products of carbohydrates – and possibly even nitrated products of protein (yellow xanthoproteic products can be formed by nitration of aromatic side chains of tyrosine, tryptophan and phenylalanine).
See my most recent two postings for details.
Geber, who in his day was regarded as an alchemist, and thus viewed with deep disapproval by the Church, had used Geber as a pen name (it’s complicated, being an attempt it would appear to pose posthumously as an much earlier Arab alchemist). However, a strong case has been made for identifying the pseudo-Geber as the Franciscan monk, Paul of Taranto.
Geber/Paul are credited with the first clear recipe for generating nitric acid and accompanying oxides of nitrogen by calcining a mixture of metal nitrates and sulphates, initially in the form of fumes from the reaction vessel. I am coming round to the view that those fumes could have been used to produce the image we see on the Shroud – as oxidation products of carbohydrates – and possibly even nitrated products of protein (yellow xanthoproteic products can be formed by nitration of aromatic side chains of tyrosine, tryptophan and phenylalanine).
See my most recent two postings for details.
(Links inserted)
Conc.nitric acid is on order. Rest assured I’ll be testing the hypothesis at the earliest opportunity, at some risk to my lungs.
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