Good Chemistry Questions

imageA reader who is a high school chemistry student writes:

In Rogers’s book on page 78 I read that “Image color can be chemically reduced with diimide, leaving colorless fibers.”  I’ve seen this mentioned on several websites and I’ve read that the image does not respond to ordinary bleaching.

My teacher and I looked it up in Wikipedia. Neither one of us can understand what it says.

What does it mean?  What does it rule in or rule out? 

Good questions? I just looked up reductions with diimide in Wikipedia and I could not understand it either.

18 thoughts on “Good Chemistry Questions”

  1. Looks like we need some fairly sophisticated organic chemistry knowledge (Where’s Colin when you really need him?) You have to be very careful with the nomenclature. Diimide = diazene isn’t diazine and isn’t diamide.

    My reading of diimide is that it’s used for preparation for certain stable plastics – polyiimides not polyamides. An Encyc Brit extract if you can make any sense out of it:

    “Polyimides are polymers that usually consist of aromatic rings coupled by imide linkages—that is, linkages in which two carbonyl (CO) groups are attached to the same nitrogen (N) atom. There are two categories of these polymers, condensation and addition. The former are made by step-growth polymerization and are linear in structure; the latter are synthesized by heat-activated addition polymerization of diimides and have a network structure.”

    “Network polyimides are formed from bismaleimide and bisnadimide precursors. At temperatures above 200° C (390° F), bismaleimides undergo free-radical addition polymerization through the double bonds to form a thermosetting network polymer. Bisnadimides react somewhat differently at elevated temperatures. The nadimide group first decomposes to yield cyclopentadiene and maleimide, which then copolymerize to form the network polyimide structure.”

    “Polyimides are amorphous plastics that characteristically exhibit great temperature stability and high strength, especially in the form of composites. They are used in aircraft components, sporting goods, electronics components, plastic films, and adhesives.”

    I’d be guessing that Ray Rogers discovered that image discolouration occurred when image fibres were reacted with diimide.

  2. On searching this blog, I found that in May of 2012, Thibault Heimburger wrote in a comment:

    Diimide was in fact used by Adler on colored fibers among 21 solvents employed in dye extraction tests. Only hydrazine (very slowly) and diimide (a strong powerful reducing agent) could bleach the yellow color of image fibers.

    This test only show that the color is not a dye and that the color is only at the surface of the fiber. Rogers wrote clearly :” Up until this time, we had assumed that the image color was a result of chemical changes IN the cellulose of the linen; The most likely change would involve the dehydration of the cellulose to produce conjugated double bonds system. Adler’s observations strongly suggested that the cellulose was not involved in image formation”.

    If the color is only in the pcw, you’ll find exactly the same result because the pcw is a thin surface layer. The cellulose is not involved. The fact that diimide leaves undamaged fibers behind shows only that it can not destroy or modify the strong cellulosic structure of the secondary cell wall. It is not surprising. But, because diimide is able to bleach the colored fibers, the chromophore carrier is likely a non-cellulosic structure at the very surface of the fiber. No more no less.

    It is the same for all the other properties found by the STURP, Rogers etc..regarding the chemistry of the image. To my knowledge there is no known fact able to distinguish between the 2 possibilities.

    However the fact is that Rogers never wrote the world primary cell wall. Why ?
    Here we must remember that he was fascinated by the ( true ) fact that the image appears to be more dense in the dark bands than in the light bands. He thought that the bands seen on the Shroud could be explained if there were more impurities left after washing and bleaching in the dark bands than in the light bands.

    Therefore everything makes sense : dark bands = thick impurity layer = dense image.
    ALL the impurity layer hypothesis is based on this hypothesis.

    But the fact is that this hypothesis is very controversial.

    For example, many textile experts think that the bands can be explained by the heterogeneity of the density of the threads (something which is often observed in ancient fabrics).

    Dark bands = more threads = more fibers = more “pcw” = dense image and vice versa.
    In my opinion, Rogers did not even think about the pcw as a possible color carrier because he found very early a complete reliable hypothesis able to explain all the observed facts. This is human.

    But recently, on the basis of the description of the pcw by some experts, we found (in SSG) that all the known microscopic, macroscopic and chemical properties could be explained if the image were the result of some kind of dehydration-oxydation of the hemicellulose found in the pcw.

    Both hypotheses are possible but the pcw hypothesis does not necessarily imply the complex process required to explain the impurity layer.

    1. Quote: “However the fact is that Rogers never wrote the world primary cell wall. Why ?”

      Most probable answer: Simply because, at the time he was doing his research, no one (namely : Fanti) had yet to come up with the primary cell wall hypothesis as a possible solution for the image chromophore. Therefore, Rogers, even if he knew perfectly well the composition of a linen fiber, including the PCW (in his writings, he makes some specific references to the composition of the external part of the fiber, including hemicellulose and pectin), had no need to talk specifically about that external part of the fiber. We must understand that his conclusion didn’t include at all the linen fiber (including the PCW) as part of the image chromophore, but only a thin layer of carbohydrate impurities, which left the whole structure of the linen fiber intact (and, for him, this was proven by the ghosts of color that leave a clean fiber behind and the diimide reduction of the color, which also left a clean fiber behind).

      Quote : “Therefore everything makes sense : dark bands = thick impurity layer = dense image.
      ALL the impurity layer hypothesis is based on this hypothesis.”

      Comment: That’s unfair to Rogers to reduce his hypothesis to such a simple premise. In fact, along with this observation of the bands, Rogers hypothesis was mainly based, as I already said, on the observation of the ghosts of color that leave a clean fiber behind and the diimide reduction of the color, which also left a clean fiber behind and also on the FACT that traces of starch had been found on the STURP samples (first by McCrone and, later on, confirmed by Rogers himself). Also (and this is important), we must note that Rogers, thanks to his preliminary tests concerning his image formation hypothesis, was able to prove that such a thin layer of carbohydrate residues on the top-surface of a linen cloth were able to get colored with the same kind of coloration as the Shroud image when exposed to a post-mortem gas like ammonia, which reinforce the credibility of his chromophore hypothesis…

      1. At the end of my previous comment, I said “which reinforce the credibility of his chromophore hypothesis…”

        I should have add this: as well as the credibility of his whole image formation hypothesis.

  3. Much simplified, but the color is a property of the presence and arrangment of double bonds. Double bonds result from the sharing of electrons (two pairs). Oxidizing and reducing agents function by promoting the loss or gain of electrons-this alters the original electron arrangement. Altered arrangement results in loss of color.

    1. Not for Rogers… He thought the image was the product of a dehydration of a thin layer of carbohydrate impurities mainly made of starch and some other components (like maybe saponaria).

    2. Concerning the idea that the image on the Shroud is the result of oxidation of the fibers, here’s what we can read in Ray Rogers’ book: “The first steps of the Maillard reactions are rather fast at much lower temperatures, and they produce colorless compounds (for example, glycosylated-proteins). The rates are even higher at body temperatures; however, they
      increase by factors between two and three for each 10°C (18°F) increase in temperature. The colorless compounds are unstable, and they rearrange to give brown polymeric materials, melanoidins, most of whose structures are still unknown. It takes some time at lower temperatures for the color to appear. The color IS NOT a result of oxidation.”

      Elsewhere in his book, we can also read this: “Prof. Alan Adler of Western Connecticut University found that the image color could be reduced with a diimide reagent, leaving colorless, undamaged cellulose fibers behind. All image color resides on the outer surface of the fibers. This confirmed spectral data that indicated that the image color was a result of complex conjugated double bonds; however, it proved that image color was found only on the outer surfaces of colored image fibers. Until this time, we had assumed that the image color was a result of chemical changes in the cellulose of the linen. The most likely change would involve the DEHYDRATION of the cellulose to produce conjugated-double-bonds systems.
      Adler’s observation proved that the cellulose was not involved in image formation.”

      Note that, in Rogers language, when he say that “the cellulose was not involved in image formation, he mean the whole linen fiber, including the most external part named “primary cell wall”.

  4. What is the final result of diimide (a powerful reducing agent) treatment on images produced by Corona Discharge ? … and on images produced by VUV excimer laser irradiation ?
    It is possible to see the result of these treatment (on linen fibrils) using the UV and IR controls. But …
    Where are these UV-(and Vis)-IR controls ? I see nothing.
    Where is the control (ncluded the nano-mechanical control) on treated thin layers ? I see nothing.
    Where are the nanomechanical comparisons (on Maillard, CD, VUV excimer laser treatments … and with the material as such as it is !) before and after the treatment with N2H2 ? Sorry. I see nothing.
    Perhaps there is alot of work to do … and few money …

    1. Quote: “What is the final result of diimide (a powerful reducing agent) treatment on images produced by Corona Discharge ? … and on images produced by VUV excimer laser irradiation ?”

      Comment: Those are VERY GOOD QUESTIONS that DiLazzaro or Fanti or anyone else has been able to answer yet (to my knowledge at least)… I guess that if it is so, it’s simply because no one (starting with DiLazzaro and his team) have chosen to make the test, which would probably discard their hypothesis right away, because I seriously doubt that a diimide treatment of their oxydized samples would be able to remove the color and leave a clean linen fiber behind as it was the case for the colored fibers of the Shroud…

      1. You should read: “Those are VERY GOOD QUESTIONS that DiLazzaro or Fanti or anyone else has NOT been able to answer yet (to my knowledge at least)…”

    2. Here’s another test DiLazzaro should do with his oxydized samples: Try to apply sticky tapes on it with a similar amount of pressure as Rogers used in Turin and see if he can find the same kind of ghosts of color on the tapes. Again, I seriously doubt he could find any… And if my guess is good, that would also be enough to discard his hypothesis right away. Same thing for Fanti and his corona discharge hypothesis.

    1. This was a joke, really… At least, they ended up adding the possibility that the chromophore is located in a layer of impurities…

  5. Thanks to Alvin, all excellent arguments for Rogers’ chromophore hypothesis, image is on starch layer, image dissolved by diimide, leaves unaffected linen fibril behind.

    However: The suggested diimide test on the Fanti & DiLazzaro treated samples might not have a starch layer. Also likewise Colin’s and Hugh’s samples probably also did not have starch layers. Their tests all need to be repeated on Edgerton type linen with a starch layer, then tested with diimide, before their hypotheses can be properly evaluated. Does scorching, excimer lasers work when a starch layer is present, and are their images removed when treated with diimide leaving an unaffected PCW behind?

    1. Quote: “The suggested diimide test on the Fanti & DiLazzaro treated samples might not have a starch layer. Also likewise Colin’s and Hugh’s samples probably also did not have starch layers. Their tests all need to be repeated on Edgerton type linen with a starch layer, then tested with diimide, before their hypotheses can be properly evaluated.”

      Reply: I agree with you. And between you and me, the fact that they didn’t made their coloration tests on proper samples (i.e. samples that would have been made with the Antique technology, which would have created a thin carbbohydrate coating on the surface) is a very negative aspect of their test plan and, simply for this reason, their results must be considered with high suspicion in regard of the image formation that occured on the Shroud.

      Then, you ask: Does scorching, excimer lasers work when a starch layer is present, and are their images removed when treated with diimide leaving an unaffected PCW behind?

      THAT’S THE QUESTION!!! And in all logic, the answer should be “no” since their coloration processes are directly affecting the PCW of the linen fiber. One thing’s for sure: DiLazzaro and Fanti have never show us any kind of proof that their coloration results is the same thing, chemically speaking, as what Adler saw on his Shroud sample. They must do those kind of comparison tests if they want to get some credibility.

  6. I wish to thank you for your interventions and points of view. So… Are we able to do anything on linen fibrils ? I believe that some simple experiments can be performed. See for example : an exposure with an excimer lamp on treated and not treated linen samples.

    You can read under the address :
    http://www.resonance.on.ca/excimer.htm

    >What is an Excimer Lamp ?
    >Excimer refers to the bound excited upper state of a molecule
    that breaks apart when a photon is emitted.
    >Resonance excites Excimer emission from its lamps
    with a proprietary RF power supply.

    (Some of the UV emission wavelengths for various gas fill
    and window combinations are shown)

    >BETTER THAN LASERS = Excimer lasers are typically only 1 to 3 % efficient …

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