Here's the first known recipe (in precise detail) for making nitric acid fumes (which might, just might, have been used to produce the Shroud image via its propensity to oxidize and 'nitrate' (verb) organic matter, turning it sepia or yellow-coloured in the process).
"Take a pound of Cyprus vitriol, a pound and a half of Saltpetre, and a quarter of a pound of alum. Submit the whole to distillation, in order to withdraw a liquor which has a high solvent action. The dissolving power of the acid is greatly augmented if it be mixed with some sal ammoniac, for it will then dissolve gold, silver and sulphur"
Cyprus vitriol is copper sulphate, saltpetre is potassium nitrate, and alum is potassium aluminium sulphate. (Sal ammoniac is ammonium chloride, but is not needed to generate nitric acid).
Here's a mechanism that has been proposed for what happens when a simpler binary mixture of copper sulphate(CuSO4) and potassium nitrate (KNO3) is heated to a high temperature (600 degrees C or higher). The chief end product, nitric acid, is shown in red ( HNO3)
These days the reaction is accomplished faster and more easily by heating a mixture of potassium nitrate and concentrated sulphuric acid, H2SO4, in a glass retort, or other all-glass apparatus, i.e. no corks, rubber bungs or other organic matter.
The nitric acid collects as a liquid in the cooled receiving flask on the right. It will be yellow or brown due to dissolved nitrogen dioxide (an impurity). There may be other oxides of nitrogen too (thus the references to NOx to avoid being too specific)
So what's this got to do with the Turin Shroud?
I propose that the Turin Shroud image may have been formed by a reaction between nitric acid and/or nitrogen oxides (NOx) acting upon organic matter, notably carbohydrates (oxidation) and even protein (nitration). It may even account for the blood that is "too red".
I provisionally call it the HNO3/NOx fumigation theory.You read it here first, correction - second. I dropped some hints yesterday on shroudstory.com. (See later comments). The key concept is that of fumigation, note, with relatively little liquid water. Details to follow in the next days and weeks (nitric acid is on order for a new round of acid experimentation, close on the heels on my H2SO4 mini-project - see the posting immediately preceding this one)
Methinks that'll do for now. I'll give details in future postings, and suggest how the hypothesis can account for a considerable number of Shroud characteristics (the latter collectively earning it the description "enigmatic") and potentially be tested, possibly falsified. Please note: it's just a hypothesis for now: my interest is less to do with debunking the authenticity of the Shroud, and more to do with trashing the absurd notion that the Shroud HAS to be of supernatural origin. See that woeful article in the Independent, December 2011, the one that prompted this blogger/retired biomedical scientist to go 'mixing it' with the purveyors of pseudo-science.
On Pseudo-Geber/Paul of Taranto: preview of William R.Newman's critique: