Tilting at Ferric Windmills

As documented last week, I contacted a journal about very questionable methods used to conclude ferric iron could be detected by fluorescence methods in water. I was already aware that this was not the only occurrence of a research group failing to properly account for the aqueous solution chemistry of Fe³⁺ in their studies. With a reignited hyperawareness about this problem in the fluorescence sensing field, I noticed another study making similar mistakes while catching up on recent literature this week. I alerted the EIC of this journal to the problem as well, and got a completely different response with respect to both the scientific and peer review concerns. Since this is an ongoing dialogue, I will not comment any further until the issue is resolved. This second incident prompted me to conduct a more thorough investigation of the underlying prevalence of these protocols in Fe³⁺ sensing.

Counts of papers containing questionable ferric sensing methodologies.
*indexed in webofknowledge as of 3/26/205.

Using webofknowledge, I searched the combination of (ferric OR Fe(III) OR Fe³⁺) AND (sensor OR probe) AND (water OR aqueous OR buffer) AND fluorescence. To decrease the volume of references to analyze, I limited the results to those from journals published by the ACS, the RSC and Wiley since they have a reputation for publishing reliable sensor papers (reducing the number of results from ~500 to ~150). I then went through the search results looking for evidence that the experiments would be at risk for giving spurious results. I am not sure about the exact speciation/stability of Fe³⁺ in mixed organic/aqueous solvents; however, my experience suggests that any significant amount of water will be problematic. I excluded several studies using 1% aqueous content in solvents like THF and methanol, as that seemed to be a relatively safe protocol. Anything with 20% or more water made the "suspicious list". The overwhelming majority claimed to work in pure water, aqueous pH ~ 7 buffer or with 50% or less organic solvent added to water/buffer. There are many fewer (not counted) that describe protocols for working and handling Fe³⁺ in acidified aqueous solution, and many others using pure organic solvent (also excluded from consideration). Of the 150 results, 51 contained possible problems. The results broken down by publication year and journal name are shown in the figure above.

The results are quite informative. Before the Rurack paper in 2005, there were no Fe³⁺ sensing papers in ACS/RSC/Wiley family of journals using water (his paper has been cited >250 times). My paper showing the errors in Rurack's aqueous results was published in 2010. The yearly trends however, suggest that the acceptance of questionable (invalid) Fe³⁺ titration protocols are increasing rather than decreasing. Presumably, every published paper using similar methods provides unwarranted precedence for adoption in future studies. Whether there is a connection or not is unclear, but Inorg. Chem. where my paper was published, has not published a problematic paper in the Fe³⁺ sensing field that I can find.

Full disclosure, there are a few papers in this collection that are difficult to analyze, particularly those from the polymer/materials literature. A more thorough investigation would be required to fully evaluate the results in detail. Furthermore, some of the studies have ambiguous or nonexistent experimental protocols in the paper and/or the supporting information, which makes evaluation difficult or impossible. If procedures for measuring/adjusting the pH are not listed, I assume that this was not a consideration. A few papers don't even list the counter ion for the Fe³⁺. Also, I excluded papers that may have had questionable handling of Fe³⁺ solutions (selectivity studies), but the Fe³⁺ response was not a significant component of the paper's discussion/conclusions. The 51 papers all attempt to conclude something specific about Fe³⁺ detection in aqueous solution. No papers from Elsevier or Springer were examined.

There are some common issues in many of the 51 papers. For example, making stock solutions of FeCl₃ in water by just mixing (i.e. without adjusting the pH to <4), and titrating Fe³⁺ into neutral aqueous solution. Some use phosphate buffer, which would generate Fe(PO₄), a water insoluble salt (assuming all the Fe³⁺ wasn't already precipitated as insoluble Fe(OH)₃). A cringe-worthy method used in more than one paper to confirm Fe³⁺ binds to the sensor in aqueous solution, is mass spectroscopic detection of the ferric complex prepared in methanol. I have no doubt that they detected the complex, but Fe³⁺ in methanol is completely different than in water. The MS data in methanol does not confirm anything about the species that are (not) present in aqueous solution. 

What does one do in such a situation? Even if I was somehow asked to referee every paper on Fe³⁺ sensing, there were more papers on the topic published last year than I could possibly handle, even if they were the only kind of requests I received/accepted. A broad search suggests an upper limit of 190 Fe³⁺ sensor papers were published in 2014. I have no desire to comb the literature and complain to editors/authors every time I find a problematic paper. I've already published a paper in a good journal that includes a cautionary tale about these issues, but it does not seem to have permeated the sensing field zeitgeist. As I mentioned in the previous post, it's discouraging to find out that some individuals need a reminder about the relevant/underlying undergraduate inorganic chemistry. I have no doubt that researchers in other fields can point to similar problems in the literature on other topics. How does one effectively get through to journals, peer reviewers and researchers without wasting time that should be spent on other aspects of academic science? It seems antiquated in the information age that such mistakes should persist and be perpetuated, but the traditional practice of publishing an opposing research study is the only clear recourse.

Metal sensing malarkey: (or the expected virtue of ignorance)

To paraphrase Stephen Colbert, "who's not citing me now?" It's a refrain that many researchers can identify with, but only a small part of why I was motivated to write this post on peer review, journal policy and bad science. A little background first. A couple of months ago, I attended a research presentation that covered several papers on fluorescent sensors. My experience with fluorescent sensors dates back to the late 1990s and early 2000s when I completed my Ph.D. thesis on zinc probes with Stephen Lippard at MIT. At the time we started, fluorescent sensors for metal ions were still a niche area in inorganic/bioinorganic chemistry. Now, it's a widespread topic of research. As many realize, your Ph.D. work will follow (haunt) you long after graduation, even if you no longer actively work in that area. My group published a couple of papers on fluorescent probes for ferric iron 5 years ago, but that was the last time I actively worked in the area. Despite moving on to other topics of inquiry, I am still inundated with referee requests on fluorescent sensor papers, so I remain familiar with the progress and problems in the field.

The presentation focused on two papers published in ACS Applied Materials & Interfaces on fluoride and iron sensing respectively. I questioned the lead author giving the presentation about the validity of the methods and data interpretation, but failed to make any headway or get any concession that there may have been problems with the protocols or conclusions. So-called "post-publication peer review" has become rather controversial over the last few years as social media has facilitated the community's ability to discuss published science in an open forum. The scientific community becomes incensed in cases of fraud or plagiarism, although journals have often reacted more negatively to those who exposed the problems than to those responsible for the actual infractions. After consulting with several other experts on the underlying science and scientific publishing, I sent an email to the EIC of the journal detailing the problems with the papers. To be clear, I did not, and I am not making any accusation of misconduct.* Serious mistakes were made in the research that in part, or in whole invalidate the conclusions of the studies. Furthermore, it is troublesome that these issues were not addressed during the peer review process.

The EIC responded after several days promising to address each paper in a separate message. His response to the fluoride paper was the only course of action would be to submit a peer reviewed comment (providing this as an example) where the author would have a chance to respond, since the paper had been in print for nearly 2 years. I did not find this to be a particularly satisfying response since any publishable comment would need to be supported with new information. Essentially collecting the data and conducting control studies that should have been requested by peer reviewers. With the current state of knowledge, a potential published comment could be summarized as "I think you're wrong" and speculation, which is not any better than what was done in the paper. Data-free speculation does not not usually hold up to peer review, so reluctantly I published my criticism on pubpeer with the hope that anyone seeking to follow-up or use this chemistry would be wary of the authors' conclusions. This is the greatest risk in a case of erroneous research, which makes it similar to some issue encountered in cases of data falsification. Any time spent trying to use flawed science, wastes time and resources that could go toward more productive efforts. Coincidentally, I came across this paper today on fluoride sensing that invokes attack on a positively changed ring (albeit a different heterocycle), which was my initial instinct for an alternative mechanism in the disputed study. I'll have to compare the data and see if it gives me any new insight.

As for the iron paper, I never received the promised response. About 6 weeks after the initial inquiry, I wrote again asking for an update. After receiving nothing during the last +2 weeks, I am once again in the position of not having any particular recourse other than forgetting about it, or providing public post-publication peer review. Of the 2 papers, the iron sensor annoyed me more, because it repeats the same mistake made by another group that my group investigated and published as part of a larger study.

In a 2005 JACS article, Rurack claimed his Fe³⁺ responsive sensor also worked in aqueous solution. The only significant difference between the Rurack sensor and the new one is the receptor for the metal ion; however, both rely on the same PeT signal transduction mechanism where coordination to the aniline nitrogen atom is the key event. Several years after the Rurack paper was published, my group attempted to use the same receptor for a different application. We spent many months working on the system and eventually had to re-evaluate the Rurack data because our observations did not match what had been reported. We ultimately demonstrated that while Rurack's sensor did bind and respond to Fe³⁺ in organic solvents that lacked alcohol or carbonyl functional groups, the fluorescence signal in water was due to protonation of the aniline nitrogen atom, which mimics an Fe³⁺ response. We were fortunate to still be able to develop an interesting story even though we started our investigation with a flawed premise from a published paper (in JACS!). In a similar manner, the new Fe³⁺ sensor paper provides the opportunity to examine both pre- and post-publication peer review in this post.

The error the authors made in new paper is essentially the same – you absolutely cannot titrate Fe³⁺ into aqueous solution unless you use use a complexing ligand (e.g. citrate, which has a log K > 10 for Fe³⁺ and would therefore bind the metal ion more tightly than the sensor) or work at pH ≤ 3. In aqueous solution, Fe³⁺ rapidly hydrolyzes to Fe(OH)₃ plus three equivalents of H⁺. The pK_as for the 1st three deprotonation events are 2.2, 2.9 and ~6. This neglects multi-Fe processes that are also possible and have similarly acidic pK_as. This is not an obscure fact, but textbook chemistry that would be covered in a standard undergraduate course. It's a fundamental concept in bioinorganic chemistry used to discuss the importance of siderophores in the acquisition of iron by microorganisms and the acquisition/transport/storage of iron by higher organisms using proteins.

The authors perform their fluorescence assays in 9:1 H₂O-CH₃CN. The water is not buffered and the authors do not report the pH at the beginning or the end of the fluorescence titration. A back of the envelope calculation shows that at ~150 equiv of Fe³⁺ added (~1000 μM Fe³⁺), the pH of the solution should reach ~3 (the approximate point at which Fe³⁺ hydrolysis no longer occurs and Fe³⁺ persists in solution). This is also the point at which the fluorescence response levels off for the sensor. The calculation is based on the use of deionized water without accounting for dissolved CO₂, not that it would make a huge difference. CH₃CN can act as a metal-binding ligand, but CH₃CN does very little to stabilize Fe³⁺ in water. The authors go on to claim that reversibility of the fluorescence response with TPEN (tetrapyridylethylenediamine), a strong metal chelator, demonstrates that the fluorescence response is Fe³⁺-induced. This is also a flawed conclusion because the pK_a of a protonated pyridine is about the same as a protonated aniline (both pK_a ~ 5) and the aliphatic amines of TPEN are even more basic. Coordination (protonation) of the aniline nitrogen atom drives the PeT process responsible for the fluorescence response. TPEN can act as a base as well as a chelator, and the authors use a huge excesses of TPEN to demonstrate reversibility (60 equiv or 360 equiv of N bases). There may be some modest equilibrium between [Fe(Sensor)]³⁺ and [H(Sensor)]⁺ at pH<3, but the authors are observing a H⁺-, not an Fe³⁺-based fluorescence response in their titration. The argument is further supported by the receptor being used. Ethers are notoriously poor metal binding ligands in water. It would be very surprising if a cryptand ligand, even one with as many donor groups as the one in this sensor, could stable an Fe³⁺ complex with in water. The low affinity for the purported "[Fe(Sensor)]³⁺ complex" based on the fluorescence data supports this conclusion.

Returning to the Rurack report, the erroneous aqueous chemistry accounted for perhaps 25% of the discussion/conclusions in the paper. The rest of the Rurack paper is correctly interpreted (and an interesting counter-intuitive inorganic story). The flawed methodology accounts for 100% of the discussion/conclusions in the new paper. In my opinion this paper should be withdrawn; however, the EIC's lack of a response suggests that this isn't going to happen. I'd also like to contrast the response I got from the editor at Inorganic Chemistry to the one I got from ACS Applied Materials and Interfaces. Granted, I was trying to published a completed study in Inorg. Chem., but it should not be necessary to conduct months worth of work to prove something that only requires an understanding of basic inorganic chemistry. The Inorg. Chem. editor carefully handled the situation and facilitated a review of the conflicting data by the original author. I recall that I might have sent the EIC a note afterwards commending the editor who handled the situation. To his credit, Rurack completely supported the publication of our paper. The only unfortunate thing is that there is no indication anywhere that the original JACS paper contains a flawed set of experiments except in our paper. I still see this paper cited periodically as evidence that Fe³⁺ sensing can be done in aqueous solution. 

As an aside, our Inorg. Chem. paper was kind of an "end of the innocence" moment for me in scientific publishing. As a recent news story on pubpeer indicates, you can't always believe what you read in scientific journals. As someone who looks at sensor papers regularly, fluorescence might be the most misinterpreted spectroscopic assay used in chemistry. Fluorescence is an easy to execute and readily available technique, but there is a great tendency to interpret the results without acquiring additional supporting data (e.g. absorption spectroscopy, product analysis, etc.). As part of the Inorg. Chem. paper, my postdoc was trying to obtain a crystal structure of the Fe³⁺ complex of the ligand. After many failed attempts, he tried with Cu²⁺, and to our surprise got a structure containing only Cu¹⁺. Another colleague in the fluorescent sensing field, pointed us in the direction of a synthetic paper where Cu²⁺ in CH₃CN is used as a 1 electron oxidant (by forming [Cu(CH₃CN)₄]⁺). This was clearly what happened in our crystallization as we used CH₃CN as the solvent. Despite our attempts to educate the fluorescent sensor community about the dangers of using Cu²⁺ in CH₃CN, this is still a common practice. There are dozens of ring-opening spirolactam probes for Cu²⁺. These probes are usually based on rhodamine fluorophores, which have 2 embedded aniline groups, and give a terrific fluorescence response in CH₃CN; however, everyone attributes the signal transduction mechanism to coordination/Lewis acidity of Cu²⁺, and ignores the possible contributions of redox chemistry.

There are clearly problems with peer review. In going through my significant backlog of TOC alerts today, I realized that RSC Advances moved to a 100 issues/year publishing schedule in 2014. This is a tremendous number of papers for a single journal, which requires a correspondingly huge number of peer reviewers. Inevitably, the same people who make mistakes in their research will be asked to review papers on similar science. This lets more errors slip through to publication and propagates errors in the literature. So what should editors do when they are alerted to a potentially serious problem? "Nothing" does not seem like an appropriate answer. Is pubpeer the the right pathway? It appears that some journals are very resistant to changing the status quo, and unless the pubpeer comments are linked to the articles, post-publication peer review may go unnoticed. It also remains to be seen if flawed protocols/conclusions will generate the kind of impassioned response that accompanies cases of scientific fraud; however, anyone who has wasted time with someone else's scientific mistakes surely has an opinion they will share without much prompting.

Update 3/22/15:
A note added in proof: the same group has a similar K⁺ sensor using a very similar receptor. The amides from the Fe³⁺ system are replaced by anilines, which would make metal interactions stronger. This sensor does not respond to Fe³⁺; however, the authors used buffered water, which means that protons from the are prevented from interacting with the aniline fluorescence switch. There is almost certainly an impact of having 3 "basic" aniline nitrogen atoms in the receptor as the amount of buffer (5 mM) is low compared to the added metal ions.

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*The PI has since move to NJIT as a Dean, which would suggest the research group at UCF is no longer active. He is and was listed as a member of the editorial advisory board for ACS Applied Materials and Interfaces. While it is not uncommon and should not be problematic for board members to publish in the journal for which they serve, this may make some readers more suspicious about the impartiality of the peer review process.

Periodic table challenge

There was a phenomenal response to my blog post on the periodic table with emphasis graphic (thanks everyone!). While I still hope to uncover more information about the history of the graphic and gain insight into what Sheehan thought about it in his later years, I suspect that Sheehan was always aware that the relative sizes of the different element blocks did not accurately represent the abundance of the elements. For the target audience of pre-college (elementary?) students however, it no doubt succeeded fantastically in generating curiosity about the periodic table and stimulating interest in chemistry. As I hope was clear, my criticism was not directed at Sheehan's pedagogical efforts but rather at the indiscriminate spread of an inaccurate "meme" portrayed as a truism. The Sheehan periodic table appeals to both our aesthetic sensibilities as well as a human desire to simplify the complex. For the same reason it was an effective outreach tool, it became the perfect mechanism to propagate misinformation.

As several have pointed out, this will not be the last time Sheehan's graphic surfaces. We can point of the errors in the graphic every time that it is shared (maybe using my blog post), but a better approach would be to displace it from the zeitgeist. Since I lack the necessary artistic skills, I'm issuing a challenge for someone to create a periodic table that illustrates relative abundance. Sadly, I can't think if anything to offer as a reward, unless there is a sudden uptick in demand for signed reprints of my papers. 

As I cited in the original blog post, several versions of the periodic table showing abundance exist; however, each have shortcomings. The new periodic table with emphasis should meet the following criteria:

1. The periodic table must be visually striking. It should be more aesthetically appealing than Sheehan's graphic. It must encourage sharing and therefore promote education.

2. The periodic table must show all the naturally occurring elements (i.e. at least up to neptunium, element 94). Obviously, this the hardest thing to achieve. As we've pointed out, the magnitude of the difference between most abundant and least abundant elements precludes presentation on anything resembling the standard periodic table. The weakness of the existing elemental abundance cartograms and the Google table is that one could conclude that rare elements do not exist. Using Google's periodic table as an example, it is accurate to say that astatine is present at 0 ppm in the Earth's crust, but it is incorrect to say astatine does not exist on earth. If one looked in locations with deposits of radioactive uranium and thorium ores, astatine would be detectable. Google also shows radon at 0 ppm. If radon was nonexistent on earth, radon abatement systems would be relegated to the dustbin of pseudoscience with the QRay bracelet and rhino horn. Radon can be found at approximately parts per trillion in the crust, but concentrated in uranium and thorium ore. 

While the cartograms pass criteria 1, Google's periodic table offers nothing beyond a standard visual. The same lack of artistry applies to all the other abundance tables that I have found.

To get people thinking, I have the skeleton of 2 possible ideas

A) An interactive periodic table that operates like Google Earth. A wide view would show the abundant elements, and the less abundant would come into view as the user zooms in closer. The big difference between Google Earth and this hypothetical periodic table is the amount of zoom required. The transition from a complete map of the continents down to the the standard street level map requires zooming through approximately 6 orders of magnitude. The abundance of elements is a much larger range of values (ca. >20 orders of magnitude).

B) A 2-fold Sheehan-inspired periodic table. The basis for this would be a color coded log scale. Colors would follow the electromagnetic spectrum such that each order of magnitude corresponds to a color (e.g. 10^-16 abundance = violet with colors red shifting as the magnitude increases). Within a given color/order of magnitude, the blocks are sized relative to one another similar to Sheehan's graphic and cartograms.

To get you started, here's one possible resource for finding the amount of the elements in the crust or oceans.

Periodic Table with {wildly inaccurate} EMPHASIS

Studies show that scientists and those interested in science are susceptible to misinformation contained in memes.¹ In 1976, William Sheehan published an article entitled "Periodic Table with EMPHASIS".² This publication remained virtually undiscovered for 36 years until a series of events appears to have brought this obscure document to the forefront of chemical (mis)information. A Google investigation suggests that a Tumblr user posted a periodic table graphic with the caption "Totally in love with this image". The Radiolab Tumblr reposted the illustration, and finally io9 posted the image on its website. The unique version of the periodic table has been tweeted, retweeted, shared, +1 and liked into viral status,³ which would be quite a coup except that no one in the initial series of postings appears to have investigated or critically analyzed the veracity of the science this periodic table purports to illustrate. 

Two versions of the "Periodic Table with EMPHASIS". The version that appeared in 2012 and was subsequently went viral (top), and the original version from the article (bottom).

Take a look at the graphic (top). Anyone with sufficient background in rare elements will immediately spot problems with this periodic table (more on that later), but it's easy to see why this caught people's attention. You could get a contact high from the vintage LSD that the previously normal periodic table dropped before having its picture taken. This is probably what Salvador Dali would have produced if the periodic table commissioned him to paint its portrait. As my good friend and frequent co-author Brett mused "It looks very retro...You can smell the early 70s from the unshaven armpit between Y and Zr." After explaining on twitter for the umpteenth time that the information in this graphic was terribly wrong, I ordered the source paper through interlibrary loan.⁴ The original version of the picture is less striking as it lacks the color scheme (bottom), which as an aside does not correlate exactly with any normal categorization of elements.⁵ While it is unclear exactly who modified the original, the tie-dyed version was the one posted on Tumblr in 2012. 

To defend Sheehan, I don't believe he intended this to be anything other than a thought experiment to stimulate interest in the periodic table with children. The "paper" contains almost no information on how it was constructed. The only citations are to papers on other artistic versions of the periodic table from the educational literature. The article is 1 ¹/₂ pages long. The bottom half of the 2^nd page contains two poems written by high school students – one a ballad on Mendeleev and the other an ode to chemical bonds. The page also contains two separate lists of chemical puns. Not exactly the material you find in most scholarly journals, but a staple of internet science. I am unsure of what kind of publication Chemistry was, but the Sheehan "paper" has never been cited according to Scifinder. The composite evidence suggests that the article is from a magazine targeted toward a more general audience, not a peer reviewed journal.

So, what are the most egregious errors in this table? Tc (Technetium, element 43), At (Astatine, element 85), and Fr (Francium, element 87) are the most striking. At occurs naturally as a product of uranium and thorium radioactive decay, however, the half-life of all At isotopes are so short that less than 30 g of the element exists at any time on earth. A similar amount of Fr exists for analogous reasons. Their neighbors Po (Polonium, element 84) and Rn (Radon, element 86) exist at approximately 10^-10 and 10^-13 mg/kg in the earth's crust respectively. Small numbers certainly, but still 7 orders of magnitude greater than the estimates for At or Fr. The element boxes in the image are roughly the same size, not 10 million times larger.⁶

I discussed the table's problems with my friend Brett. His musings:

"Did I say that that table was actually impossible to display on a computer monitor correctly? I checked the math. It's amusing:

For argument's sake, let’s say that naturally occurring Tc is 10^-10 the amount of U (Uranium, element 92). There are about 6 orders of magnitude less U in the earth’s crust (at least) than O (Oxygen, element 6) or Si (Silicon, element 14) the 2 most abundant elements. So there is 10^-16 less Tc than O in the earth. I think this overestimates the amount of Tc, but 10^-16 is bad enough.

To have a visible block for Tc requires how many pixels? If you want to read the "Tc" symbol, you need at least a 6×6 pixel square by my estimate. 36 pixels for the smallest element "block" on this hypothetical table. That means the largest block (O) would have (roughly) 3.6×10¹⁷ pixels. I don't have the motivation to figure out the exact size of all the other element blocks, but the earth's crust is dominated by just a few elements, so let's say that the total pixels required for the table would be about 2×10¹⁸ pixels (this is the worst estimate in this calculation, but it would take longer to calculate exactly and it's not off by more than an order of magnitude).

I'm typing this on a screen with 1920×1200 pixels, or about 2.3 million pixels. At the same resolution as my monitor, to be able to SEE the Tc element block, the monitor would be 8.68×10¹¹ times larger. Yes, the screen would need to be 868 BILLION times larger.

I think there MAY be enough pixels on all the monitors in the world to do this. Especially now that there are so many smartphones around. Right? A little Googling reveals that in March 2014 Apple sold the 500 millionth iPhone. Let's be generous and assume that all iPhones to date had the large high-res screen size available at that time, 1136×640 pixels (A slightly bad assumption, but since each iPhone has outsold its predecessors, not a terrible assumption). So each iPhone has 727,040 pixels. The block for oxygen would require 495 BILLION iPhones to display. The entire table would require about 3 TRILLION iPhones to display.

Yikes. Looks like smartphones are still a growth market."

So just like every other meme and viral post, take things shared on the internet with a grain of salt until you do some research. Fortunately, Google has a better version of the periodic table by relative abundance. Not as groovy as the Sheehan table, but more accurate. Our analysis of the problems with the graphic are by no means comprehensive. I would encourage readers to highlight their pet peeves about the table in the comments, so this post can be a resource to educate people about the true natural distribution of the elements.

Update: 7:32 PM 12/31/14
Here are a couple of other representations of the periodic table showing abundances. These cartograms are both aesthetically appealing and informative. This one by geochemists is also interesting if not all that artistic.

Update: 3:47 PM 1/2/15
Here is an in memorium from the Santa Clara University website on William Sheehan that references his periodic table graphic. Further updates or a new blog will be posted if/when I can track down further information.

Update: 11:25 AM 1/3/15
EUREKA! After doing a lot more digging and coming up with very little from Santa Clara University, I found a J. Chem. Ed. paper from 1993 by Kathleen Carrado at Argonne. It's copyrighted material and behind a paywall. The article discusses using a black and white version of the Sheehan table as a coloring book exercise with elementary-aged students. The paper also references a 1978 calendar by Instruments for Research and Industry that used Sheehan's graphic. Confirmation pending, but this seems like where the colored graphic originated, and further proof that this table was not intended to be an absolute representation of relative abundance.

Update: 11:34 AM 1/4/15
Another calculation analogy from Brett:
A properly scaled table would cover an area of about 3×10¹² × ((58.6/1000)*(123.8/1000)) m², or 21764 km² or 8403 square miles. That’s an area about 7 Rhode Islands or 80% of the size of Massachusetts. Kind of hard to carry around or print out 

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1. This is an anecdotal observation made by one blogger, which seems to be sufficient evidence of validity in the internet age.

2. W. F. Sheehan. Chemistry. 1976, 49, 17-18.

3. What counts as viral in the chemistry world anyway.
4. I would post the paper in total, but this would probably violate copyright law. How about a link to the pdf in Google drive instead?
5. Colors correspond to relative electronegativity. This has been clipped off of some of the images being circulated. Also, the colors do not accurately represent electronegativity. See here. For example, Kr and Xe have approximately the same electronegativity as their halogen neighbors. 
6.  The Sheehan graphic has the disclaimer "To accommodate all elements some distortions are necessary. For example, some elements shown do not occur naturally", but does not provide details. The transuranium elements fit the latter characterization, nevertheless 7 orders of magnitude seems like a broad interpretation of "some distortions."

Protactinium’s Discovery Redux: Kasimir Fajans and Oswald Göhring discovered element 91 in 1913

The great Periodic Table of Videos series on YouTube a few weeks ago published a video on element 91: protactinium. Protactinium is an element that is (a) obscure and rare (b) has a confusing discovery story, and (c) had linguistic issues with its name. Given our interest in discovery, isotopes and nomenclature, we found a few details in the video that should be revisited. For an element such as protactinium, which has few applications today, an element’s entire “story” concerns how it was discovered.

The Periodic Table of Videos series is exceptional, but things go slightly awry beginning around 3:00 in the protactinium video with the still frame of Frederik Soddy & John Cranston. These two British scientists, along with Lise Meitner & Otto Hahn of Germany, are credited with the discovery of protactinium. That’s incorrect: Meitner & Hahn published their successful precipitation of element 91 in 1918, but this was not the discovery of the element—it wasn’t even the first precipitation of the element. The independent work of Soddy & Cranston, also published in 1918, also was not the true discovery.

Starting around 4:00, the professor explains that the isotope ²³⁸Pa, which has a 32,760 year half-life, was discovered by Meitner & Hahn and “a few years earlier” Kasimir Fajans discovered ²³⁴Pa. ²³⁴Pa has a much shorter half-life and was named “brevium” (Fajans’ co-discoverer Oswald Göhring is not mentioned).

Shouldn’t Fajans & Göhring be the credited as the discoverers of element 91? They beat Meitner & Hahn and Soddy & Cranston by five years! In 1913, Fajans & Göhring had three separate publications on element 91 including the precipitation of ²³⁴Pa (K. Fajans & O. Göhring, Phyik. Z., 14, 877, 1913). This work is discussed explaining “[Fajans'] was the first discovery of protactinium, but it turns out that there is a custom if several different isotopes of an element are discovered, whoever discovers the longest lived isotope, wins, and they’re deemed the discoverer.” Wait, what??? That sounds like redefining the word “discovery”!

What is explained in the video is only half the story. The other half is that Kasimir Fajans pushed the idea that the elements should be given the name of the longest lived isotope (in his 1919 book Radioaktivität und die Neueste Entwicklung der Lehre von den Chemischen Elementen). In the 1910s, isotopes were a very new idea and it was still unclear whether or not they should be treated as separate elements. Meitner & Hahn’s 1918 paper clearly claims a new “element” even though they knew they knew that their “element” had the same atomic number as Fajans & Görhing’s “element” discovered 5 years earlier. Meitner & Hahn were using the definition of the word “element” as was common in 1918 when it was still unclear how to classify isotopes. When chemists say “element” today, they clearly mean all isotopes with the same atomic number. Fajans never intended to give away the credit for element 91’s discovery to Hahn & Meitner or Soddy & Cranston. In fact, one of Fajans’ last papers defends his discovery priority.

There is one other element that was renamed based on its longest-lived isotope: radon. Radon’s discoverers wanted to call the element emanation. For decades, “radon” was only the name of the longest-lived isotope of emanation. After the name was changed, history began to forget who had actually discovered radon. Just like protactinium, people preferred to give credit to the individual or group who had discovered and named the longest-lived isotope of the element. We wrote quite a bit about the linguistic twists of radon last year in Nature Chemistry. In an accompanying blog post, we explored protactinium’s naming and discovery confusion. There is also an excellent Nature: In Your Element piece that delves into the protactinium story.

Is there is a lesson here for chemists? If you get to name something, you might get credit for discovering it, even if you didn't. That can happen both inside and outside of chemistry, which might be a more than a little disconcerting.

It’s incorrect to say that “the discover of the stablest isotope gets to name the element” as a general rule, especially today. Since most superheavy elements are created as highly unstable, neutron-poor isotopes first, only later are (slightly) more stable isotopes created. No one is ceding naming or discovery priority to anyone who years later makes the most stable version element 112 for example. The Periodic Table of Videos project is great and everyone should follow their work, but examine the protactinium discovery a little more closely to get the complete story.

- Brett F. Thornton with editorial assistance by Shawn

Winning the "War on Chemicals" by redefining victory

With some rudimentary photoshop skills I could appropriate one of Stephen Colbert's "War On _____" graphics as a post banner. Alas, I have none.

With clock-like regularity, some synthetic compound bearing the unnerving label "chemical" is brought to the public's attention. To make matters worse, the "chemical" also is identified by its proper name, an intimidating number of consonants and vowels jumbled together into a seemingly incomprehensible order to the untrained eye. The end result is most often a demand that the offending substance be expunged from existence because of the inherent risk in coming into contact with "chemicals." The public's irrational fear of chemicals has been dubbed chemophobia, which is also a popular hashtag for connecting discussions of the subject online.

The most recent dustup involves the use of azodicarbonamide in Subway's flour/bread. This instance has all the hallmarks of chemophobia: bad analogies, (wildly) exaggerated claims of health risks, insinuations of conspiracy. Chemists immediately took to twitter and blogs to defend chemicals and debunk claims that led Subway to decide to phase out azodicarbonamide. In the Pipeline had previously summarized why the risks of using azodicarbonamide are extremely small, and the Curious Wavefunction discussed the real danger of chemophobia. The response is typical of how we chemists have combated these controversies, and we are losing.

As people who spent an inordinate amount of time in institutions of higher learning (including as a career), the "defend and debunk" strategy comes quite naturally. We like education and educating. Being scientists also makes exploiting this tactic even more amenable because we've been trained to collect, analyze and interpret data. When we see dubious claims or "chemical-free" products, our instincts take over and we make solid arguments backed by science; however, we are not engaged in a scientific debate with paper reviewers or grant referees. As has been documented previously, facts don't matter in these situations. When presented with evidence that a belief is demonstrably wrong, people often become more entrenched in their position. In order to defend chemistry, we need to change course and redefine what constitutes winning an argument. What strategies should we employ? Here are some ideas, but there certainly need to be more.

As the Curious Wavefunction alludes to, the biggest problem is when fear subverts the solutions to problems that science has produced. Feeding the world's +7 billion (and growing) people using only organic farming is almost certainly impossible. It has even been suggested that much-maligned GMOs will be necessary to produce enough food on a planet suffering from the adverse effects of climate change. These are more global versions of the problems science and chemistry has produced to deal with problems of food production, distribution and storage that are essential to modern lifestyles. In the discussion of azodicarbonamide, I have only seen passing references to its use as a flour conditioner, but not a justification. Oxidants like azodicarbonamide are used to oxidize sulfhydryls in gluten to disulfides. This conditioning ultimately speeds up flour processing, which historically was accomplished by the oxygen in air and takes weeks. As a non-food chemist, I conclude that azodicarbonamide was developed in the 1960s as a replacement for bromate as an oxidant. Bromoate, like azodicarbonamide, is banned in the EU, but it is unclear (to me) what has been adopted instead.

In a case like this, the discussion should be about the process and whether or not it is the best one available. Clearly, multi-week air oxidation of flour is incompatible with modern demand and production limitations, but azodicarbonamide is also +50 year old technology. While the risks may be small (or non-existent), is there an equally effective (or superior) alternative that would be more appealing to the public? The advantage of the alternative need not be limited to public perception, they could easily be more effective, efficient or cost-effective. As Carmden Drahl tweets, this may best be viewed as an opportunity to develop new chemistry and employment opportunities. Instead of focusing on the fear aspect, overcoming chemophobia may be easier by emphasizing the benefits of the chemical process and engaging in conversations about the alternatives. Such discussions may better illustrate what the safest option is, as well as why chemistry is essential. This may even be more convincing ways to show that the current methods were actually chosen because they are the safest/best.

The language and tenor of debate also does not help to advance the cause. When someone calls for a "chemical free" version of something, chemists are quick to point out that everything is composed of chemicals. There is even a line of t-shirts and posters that aim to show everything, including the humble banana, is nothing more than a complicated mixture of chemicals. While this is unarguably correct, this undoubtedly comes across as condescending and put those propagating erroneous information on the defensive. As indicated above, this will only serve to further entrench these people into the "anti-chemical" camp. Chemists are not particularly renowned for PR and marketing skills, but the chemophobia problem has more parallels with politics than science. To shift public opinion, we must be able to change the perception of chemicals. A better approach may be to suggest an alternative to "chemical-free" for the specific case without the condemnation. We like to be right, but proving we're right is losing the debate.

This brings us to the central thread of this debate, chemophobia. Like "chemical-free," the objections to synthetic additives based on uninformed opinions can undoubtedly be classified as an irrational fear. "Chemophobia" is certainly an accurate moniker that quickly summarizes what is, or what we believe to be, the basis for someone's objections to a chemical like azodicarbonamide; however, even though it's a relatively new term, chemophobia has already become a pejorative. Name calling and insults seldom (never) persuade someone to a different point of view. Godwin's Law could readily be applied to chemistry where every argument ends when we call someone a chemophobe.

The Right To Say "Aluminum" Instead of "Aluminium": the Real Reason the Pilgrims Fled England

In the spirit of Thanksgiving, a little bit of American vs British English discussion.

A couple of days ago Kat Day wrote a blog post about the spelling of sulfur/sulphur, which started a conversation that eventually landed on the aluminum/aluminium controversy. I became aware when Stuart Cantrill brought me into the conversation on the basis of a Nature Chemistry thesis that Brett Thornton and I wrote recently on element suffixes. The aluminum/aluminium issue was mentioned in passing, but was one of many tangential anecdotes that were truncated due to limited space. A little web searching by others yielded a couple of articles by Grammarphobia and World Wide Words on the topic. Brett and I (but mostly Brett) did some more research and think there’s more here than the common knowledge. Here are some thoughts and speculation. Consider this a working hypothesis as there are pieces of the puzzle we are still chasing down.

First, the "Latin-sounding" argument is probably the reverse, as we noted in the thesis. Aluminum is too Latin-like, which was the complaint, not the reverse. We are not 100% sure about this as the Quarterly Review was a literary journal, and early 19th century English can be magniloquent. It was however, a literary argument similar to Ampere wanting to rename fluorine phtorine. Either way, Humphry Davy's original nomenclature clearly didn't stick, since everyone used aluminium. Bill Bryson's book The Mother Tongue credits Webster with pushing the aluminum spelling in America. That's plausible since Webster was big on simplifications; however, most of these were routinely ignored. As soon as he died in 1843, his heirs promptly removed many of his "simplified" words from his eponymous dictionary.

The 1870 edition of Webster's dictionary has neither aluminum or aluminium. The 1913 edition has both. We haven't been able to check all the intervening editions, but we believe the 1844 version, the last by Webster himself, has aluminum. If Webster was basing his words on Davy's chemistry texts, which is not an unreasonable assumption, he would have found the word "aluminum", which was promptly expunged after Webster died because no one was using it (just like other Webster spellings such as ‘tung’ for ‘tongue’). So the problem with crediting Webster is that no one paid any attention to aluminum before Webster died. If it wasn't Webster who changed the spelling, who did?

Wikipedia had a juicy, unreferenced tidbit in the entry for Charles Martin Hall of the Hall-Heroult Process fame. They credit Hall for misspelling aluminium on a "handbill publicizing his aluminum refinement process", and subsequently this spelling took off in the US. There is more on this in a book called "Boron Group." It adds that Hall used the -ium suffix on all his patent applications and the supposed handbill was from 1892. Hall's company (now Alcoa) was named the "Pittsburg Reduction Company" in 1888. It was changed to "Aluminum Company of America" in 1907, so clearly aluminum had supplanted aluminium by then. The archives have a lot of referrals to aluminum for the 1880s (before the 1892 handbill), exactly when Al went from curiosity to a practical metal, which is also when the nomenclature might have changed. Our hunch is that this was Hall's doing, perhaps unintentionally, but his 1889 patent says aluminium throughout. Why didn't he use the aluminum spelling that was also in use?

The Washington Monument cap, was cast from Al in 1884 just before Hall's work. The corresponding patent from William Frishmuth for refining Al from 1884 used aluminium just like Hall's patent. This suggests that the accepted spelling in the 1880s was probably aluminium, so it seems pretty conclusive that Webster's use of aluminum in the 1820s didn't stick. 

Of course ACS changed to aluminum in 1925, and IUPAC took the other route in 1990.