{"id":549,"date":"2022-02-14T23:21:00","date_gmt":"2022-02-14T23:21:00","guid":{"rendered":"https:\/\/sites.rutgers.edu\/motley-emblem\/?p=549"},"modified":"2022-02-20T17:01:56","modified_gmt":"2022-02-20T17:01:56","slug":"x-ray-fluorescence","status":"publish","type":"post","link":"https:\/\/sites.rutgers.edu\/motley-emblem\/x-ray-fluorescence\/","title":{"rendered":"X-Ray Fluorescence"},"content":{"rendered":"
\"\"<\/a>
Casey Mallinckrodt at the Penn Museum, working with the XRF Analyzer– possibly the same device that will be pointed at an instance of the Motley Emblem.<\/figcaption><\/figure>\n

The curators at the University of Pennsylvania are close to agreeing to spray a single copy of the motley emblem with some high-energy x-rays.\u00a0 We’re hoping the page will give up a few secrets about the chemical composition of its pigments.\u00a0 Just knowing the chemical composition won’t be enough to determine which pigments were used; two of the emblem’s colors are almost certainly botanicals, and organic compounds are difficult to tell apart just by knowing their atomic composition.\u00a0 But getting this work done will go a long way towards eliminating many possibilities, and give some clues to isolate the ones that remain.<\/p>\n

As I’ve been embarking on this part of this project, I have wondered what a contemporary chemist would have made of all this.\u00a0 Laurence Sterne’s marbled page began as an extended exercise in practical chemistry, as British bookbinders tried to get up to speed with Continental skill, and doing the work of recreating it has meant relearning that chemistry.\u00a0 But what we’re proposing to do, by putting one under an x-ray emitter: that’s a chemistry of a different sort, what Thomas Kuhn would call “incommensurable<\/a>.”<\/p>\n

\"\"<\/a>
William Morgan, by Thomas Lawrence (1818), Staples Hall, Institute of Actuaries. It is tempting to think that Morgan’s ashen skin\u2014especially of his hands\u2014is due to overexposure to x-ray radiation, but is more likely the result of a different chemical effect: the fading of the translucent lake pigments Lawrence was known to employ for flesh-tone effects.<\/figcaption><\/figure>\n

When William Morgan, a Welsh physician who would later emerge as a pioneer in the actuarial sciences, reported in 1785 on the glow emitted<\/a> when an electrical current was made to pass through a rarefied gas, he saw a sign of what he called “the conducting power of air.”\u00a0 And when the glow ceased, when he had perfectly evacuated the tube, he concluded that the electrical fluid simply ceased to flow.\u00a0 Had someone from our moment been there, armed with the knowledge available even in a high-school physics textbook, they might have seen it differently.\u00a0 They probably would have seen signs that there was still an electrical current.\u00a0 And they might even have been open to the idea that some sort of invisible radiation was being emitted.\u00a0 One such modern witness was Sir Richard Gregory, writing 150 years after Morgan’s experiment.\u00a0 Morgan “did not know it,” writes Gregory, but Morgan was filling the room with x-rays, “and his simple apparatus represented the first X-ray tube.” \u00a0It is just that Morgan’s metaphysical models didn’t admit the explanation of an absence as a different sort of energetic presence.<\/p>\n

There can be a danger of being like that woman at a performance of Othello<\/em>, who (Jonathan Lamb<\/a> points out) cries out from the audience that Othello is a fool for not believing Desdemona innocent.\u00a0 Someone like Gregory can wonder how Morgan repeatedly doesn’t see x-rays for x-rays– a site of non-seeing repeated (he notes) when Humphry Davies and then Michael Faraday differently confirmed his experiments<\/a>.\u00a0 But chemistry in England, in the moment of the motley emblem, was engaged in a different set of tasks.\u00a0 It was mostly of the pragmatic sort.\u00a0 England’s best chemists were manipulating materials that can be seen and felt, in order to produce other effects, also felt and seen. \u00a0The talented experimentalist William Lewis, for instance, confined his metaphysical mood to a couple of pages in the preface to his Commercium Philosophico-Technicum<\/a> <\/em>(London: 1763).\u00a0 Though he firmly believed that chemical action was owing to “bodies considered as… insensible and dissimilar parts,” those interactions receive little discussion in his treatise.\u00a0 His goal was to develop a practical course of chemistry of use in British manufactories, and while, from a theoretical perspective, it helps to commit to a plausible metaphysical theory of the stuff you’re working with, from a practical one, it was more important to develop a repertoire of procedures that might prompt chemical effects in certain situations\u2014processes like heating or dissolving in solution.\u00a0 Chemical reactions are, he concluded, “not investigable from any principles,” at least, any principles he knew.\u00a0 They can be “discoverable by observation only,” and so an active program of practical research seemed preferable to theoretical or metaphysical explorations. \u00a0What was important, he might have said, was intervening<\/a>; even if he had had the technical expertise and equipment to check for x-rays, representing by models would have been less of a concern.<\/p>\n

\"\"<\/a>
The primary photons from the X-ray tube have high enough energy that they can knock electrons out of the innermost orbitals, creating a vacancy (1). An electron from an outer orbital will move into each newly vacant space at the inner orbital to regain stability within the atom (2).<\/figcaption><\/figure>\n

Chemistry would have to wait for roughly a century for the metaphysical model involved with x-ray fluorescence.\u00a0 But it’s worth saying that that working model, the Rutherford or planetary model of atomic physics, is also a metaphysical assumption not strictly favored by current theory, I mean as an accurate picture of things as they are.\u00a0 In virtually every handbook or instruction manual on x-ray fluorescence, you will see an image of x-rays irradiating a solar-system-like atom.\u00a0 Working the device means buying into the assumption that every atom has a dense atomic core orbited at some distance by negatively charged electrons\u2014much as planets orbit the Sun. \u00a0The device registers the change when an atom’s electrons are punched out of low-level orbits by high-energy x-rays, and each atom promotes a replacement from a more concentrically distant position.\u00a0 As the electron falls, it sheds a discrete amount of energy as it goes, emitting a compensatory x-ray in a process called “secondary fluorescence.”\u00a0 That is what the XRF device reads; because each element, by this model, has its own arrangement of electrons, the precise amount of energy released in the reshuffling is a signal as unique as a monogram or heraldric crest.\u00a0 It doesn’t matter that we should really be thinking about an atom as a set of probabilistic distributions, or an electron as a smear of electrical charge.\u00a0 The Rutherford metaphysics of atomic structure gives rise to the technical apparatus of the XRF gun, and the interpretive programme that makes sense of its results.\u00a0 We need that model to put xrays to work, and interpret what they do after their done, even if the model isn’t strictly accurate, from a metaphysical point of view.<\/p>\n

But all this is by way of reflecting on the difficulty of knowing what Robert Dossie or William Lewis would have made of our efforts to put the device to work.\u00a0 When we put the motley emblem under an x-ray fluorescence device, two radically different chemical paradigms will be made to meet.\u00a0 On the one hand, there is the practical chemistry of Dossie and Lewis, not to mention the technical expertise of the apothecaries and colourmen who mixed the pigments of the page, which produced the page in the first place.\u00a0 That expertise is what I am attempting to gather in my (comparatively modest) alchemical laboratory.\u00a0 But, on the other, there are the different, incommensurable, and also essentially outdated theories of Ernest Rutherford and Wilhelm R\u00f6ntgen, that will burst into brightness when we fire up the XRF apparatus.\u00a0 We are not attempting to arrive at the Enlightenment from a position of greater enlightenment.\u00a0 Rather, we are trying to arrive at their moment, with the assumptions that made their accomplishments possible, with the tools we have available, some of which imply metaphysics that would have seemed as unlikely to them as the woman yelling to Othello from the crowd.<\/p>\n","protected":false},"excerpt":{"rendered":"

The curators at the University of Pennsylvania are close to agreeing to spray a single copy of the motley emblem with some high-energy x-rays.\u00a0 We’re hoping the page will give … Read More<\/a><\/p>\n","protected":false},"author":136,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-549","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"acf":[],"yoast_head":"\nX-Ray Fluorescence - The Motley Emblem<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/sites.rutgers.edu\/motley-emblem\/x-ray-fluorescence\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"X-Ray Fluorescence - The Motley Emblem\" \/>\n<meta property=\"og:description\" content=\"The curators at the University of Pennsylvania are close to agreeing to spray a single copy of the motley emblem with some high-energy x-rays.\u00a0 We’re hoping the page will give … Read More\" \/>\n<meta property=\"og:url\" content=\"https:\/\/sites.rutgers.edu\/motley-emblem\/x-ray-fluorescence\/\" \/>\n<meta property=\"og:site_name\" content=\"The Motley Emblem\" \/>\n<meta property=\"article:published_time\" content=\"2022-02-14T23:21:00+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2022-02-20T17:01:56+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/sites.rutgers.edu\/motley-emblem\/wp-content\/uploads\/sites\/786\/2022\/02\/Casey-xrf-analyzer.jpg\" \/>\n<meta name=\"author\" content=\"Sean Silver\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Sean Silver\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"7 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/sites.rutgers.edu\/motley-emblem\/x-ray-fluorescence\/\",\"url\":\"https:\/\/sites.rutgers.edu\/motley-emblem\/x-ray-fluorescence\/\",\"name\":\"X-Ray Fluorescence - 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