Talk:Kilogram/Archive 5

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Simpler introduction

Hi all. Sorry I have been offline for a while, I have been travelling. And sorry I don't have time to read the history log and all the detailed comments here. So with that caveat, here is my 2 cents' worth. I still prefer the version that I inserted, or some variant on it. In physics, "weight" is a force and kg measures mass, period. If Wikipedia is a scholarly encyclopedia then it should presumably reflect this. It should also note the common usage (although "commerce and trade" seems a rather grand term for this) that mass is often called weight or, if you prefer, that weight is measured in kg. I think the earlier version expressed this more clearly than the current version, but that is not surprising since I helped write the earlier version! Timb66 21:01, 2 November 2007 (UTC)

Yeah, I have to agree with you Timb66. Army1987: The treatment you have (or had) in the second paragraph was a single, linear sentence of 105 words, broken up by a serial semicolons commas, and colons. Notwithstanding Wikipedia’s shortcomings in accuracy on technical subjects (something we’re all working to fix) Wikipedia’s hallmark virtue has been its tight, pithy introductory paragraphs. That’s one reason why so darn much effort is put into introductory paragraphs: crafting compact language that is always correct is really, really tough in science. Sometimes treatments elsewhere sacrifice scientific rigor in order to get a general point communicated. I hate doing so and never resort to it if I can avoid it. Whereas everything you wrote is true, such an expanded treatment this early in the article isn’t suitable IMO. I agree with Timb66; just a short mention about weight being expressed in kilograms will suffice until the reader can get to the Table of Contents. At that point, they can pick and choose their subject, or read the entire article linearly. In either case, the interested reader will have the opportunity to read about exceptions in trade and commerce in the applicable section (in this case, at Kilogram#The_distinction_between_the_two. I note too that Gene was battling me to revert to Timb66’s version. Let’s live with it, OK? Greg L (my talk) 02:32, 3 November 2007 (UTC)

I had tried to express all that stuff more concisely, and failed. So let's keep the shorter version. (BTW, I can't understand what about 75% of the "Mass versus weight" section is doing in an article on an unit of measurement, either. The article on the second doesn't deal with what time is, and the article about the metre doesn't deal with what space is.) Army1987 10:20, 3 November 2007 (UTC)

Appropriate location for “Mass versus weight”

(Copied from last entry above.)

I had tried to express all that stuff more concisely, and failed. So let's keep the shorter version. (BTW, I can't understand what about 75% of the "Mass versus weight" section is doing in an article on an unit of measurement, either. The article on the second doesn't deal with what time is, and the article about the metre doesn't deal with what space is.) Army1987 10:20, 3 November 2007 (UTC)

Army1987: I started the subject here because 1) the Kilogram article was seriously deficient when I first started on it (here’s what it looked like; you’d have to actually read it but it was rife with errors), 2) there has long been the common misperception that the kilogram is uniquely a unit of mass and the pound is a unit of weight, so people would logically first begin their research into the issue at Kilogram, and 3) the nuances of the effect of buoyancy on mass standards and precision metrology seem to be appropriately addressed in a Kilogram article too. It has previously been suggested that a new article be created called “Mass versus weight”. Indeed, we can create such an article but it’s not the sort of article title that one would think of typing directly to look up. So you end up just briefly touching upon the subject in “Kilogram” and providing a link to the “Mass versus weight” article. I like Wikipedia’s ability to link to other articles for further reading. When done judiciously, you really exploit the strength of hyperlinks; when done to excess (like linking dates to see what the hell other totally unreleated events occurred on July 17, 1763), it burdens the article IMO. When linked properly, we write for instance, “While the weight of objects are often expressed in kilograms…” and the Weight article is one that one would type all by itself and linking to it provides a logical, handy, easy-to-remember article for further reading. But an article titled “Mass versus weight” strikes me as simply fragmenting a subject for the sake of fragmenting a subject. Few would remember two weeks later that the topic is titled “Mass versus weight” but would remember that you first go to “Kilogram” to find the link. That’s the clue that an article shouldn’t be fragmented in the first place into a separate topic: how obvious and easy-to-remember is the title of the linked article? Wikipedia is getting out of hand in this regard IMO. That’s my 2¢ anyway. Greg L (my talk) 20:29, 3 November 2007 (UTC)

Let me just get this straight: Would you be happy to move most of the discussion on the "mass vs weight" issue to the "weight" article? That seems to me to be the logical place for it, then we can keep just enough to give reasonable context to this article. --Slashme 18:15, 4 November 2007 (UTC)

Copy(?), yes, move(?), no. For two reasons:

1. People who have an interest in the distinction between mass and weight often labor under the misperception that the Kilogram™®© is uniquely a unit of mass and is somehow special whereas all other units (like the pound) are measures of weight. In many, many cases, the Kilogram article is where people will begin their search on this distinction; and
2. When articles reach a certain level of polish, they become more stable; readers feel less compelled to become “editors.” The Weight article is not one of those stable articles and is continually in a state of flux. Some articles simply attract a non-technical crowd anxious to try their hand at “correcting” something they don’t truly understand.

The Moon article was once a featured article. Check out the history on it; the article is constantly in a state of flux where there are outlandish falsehoods for several weeks and a little later, it is semicorrect. Most experts on the Moon just runs from any notion of trying to do some good there. If the “Mass vs. weight” information was moved to Weight, the topic would soon get corrupted after a few weeks into something with critical falsehoods and would be next-to-worthless unless someone who really gave a crap continually rode shotgun on it. If you don’t believe me, copy it over to Weight (don’t “move” it) and assume primary responsibility to defend it (edit warring) to keep it accurate over there for several months. I think you’d soon realize that’s no fun. We’ve all got to pull together to break out of this cycle of endless inaccuracies in technical subjects on Wikipedia. Colleges now routinely caution students against researching on Wikipedia and citing it in their work and that’s a damn shame.

I’ve seen quite a few edits occur to the Mass versus weight section by editors who wanted to improve the section; they weren’t trying to diminish, delete, or move the topic. I think the topic clearly serves a valuable purpose and is logically located. Greg L (my talk) 22:18, 4 November 2007 (UTC)

Greg, your argument for keeing "mass versus weight" here is unconvincing to me. To me, it boils down to the following. The concept of lay editing on Wikipedia is fundamentally flawed, and the explination of mass versus weight can only be preserved if an expert shepherds it constantly. Since I (greg) am only willing to shepherd kilogram that carefully, I (greg) need to keep this important explination of mass versus weight here, in kilogram.

Personally, I tell college students I'm teaching NEVER to cite Wikipedia in their writing, and I don't plan on changing that advice, no matter how good Wikipedia articles become. Wikipedia is an encyclopeida; a tertiary source. It can be a good place to go to find out basic information and sources to cite, but no encyclopedia should be cited in college level writing. Enuja (talk) 21:44, 6 November 2007 (UTC)

It seems to me that the best place to discuss "mass v weight" would be in Mass or Weight, although I wouldn't object if it were moved to its own article. I'm just an engineer, though, so my opinion may not have much... um. Sheffield Steel^talk_stalk 22:27, 6 November 2007 (UTC)

(-:

I think I agree with SheffieldSteel here. It either deserves its own article, or subsections in Mass and/or Weight. While I think it's a subject worth covering, I don't see why it should be in the kilogram article? Best, --Bfigura ^(talk) 22:37, 6 November 2007 (UTC)

I'm 100% with Bfigura, Enuja and SheffieldSteel here. Greg, I think keeping a discussion of a topic on one wikipedia article because you don't trust the people who edit another article is a Very Bad Thing. The content should go where it is best suited. I watch "weight" and "mass", and so do many of the other editors who watch "kilogram". I'm sure we can manage to keep it in shape. --Slashme 06:26, 7 November 2007 (UTC)

I also agree that a discussion on mass v weight does not belong here and should go in mass and/or weight (probably weight). And I find it rather strnge that the article on the kilogram should generate so much heated discussion. Timb66 06:35, 7 November 2007 (UTC)

Wow. OK. How about a separate “Mass versus weight” article that “Mass”, “Weight”, and “Kilogram” can all link to? Who likes that? Greg L (my talk) 20:58, 7 November 2007 (UTC)

• Wow. OK. Clearly the consensus is to move it out of Kilogram. Now we just need a clear consensus on where exactly to move it to. How about a separate “Mass versus weight” article that Mass, Weight, and Kilogram (and Newton, Kilogram-force, etc.) can all all link to? Who likes that? Logically, it doesn't seem to me that Weight “owns” the topic any more than Mass does. And its more appealing to me because transplanting the current treatment to its own article should result in pretty good stability. Can we reach a consensus for its new location as a stand-alone, tentatively titled “Mass versus weight”? Greg L (my talk) 22:02, 7 November 2007 (UTC)

Sounds good to me. I think there's probably enough said about the issue that there's justification for a stand alone article. --Bfigura ^(talk) 21:55, 7 November 2007 (UTC)

Weight currently contains a treatment of the issue of "mass versus weight," and several articles link to weight because of that discussion. If we are going to make a new article mass versus weight, this should be discussed at Talk:Weight. I created a topic there in August. One editor supported keeping the treatment of mass v. weight in weight, and Gene Nygaard and Greg L continued the argument above about the definition of weight there. I suggest that this part of the conversation should move to weight's talk page. Enuja (talk) 22:35, 7 November 2007 (UTC)

Oh, wasn't aware there was already a treatment of this there. --Bfigura ^(talk) 03:22, 8 November 2007 (UTC)

(*sigh*) Myself (Greg L) and Gene have also been arguing about the nature of mass and weight in this forum so the fact that we also argued it Talk:Weight doesn’t have any uniqueness. We only recently got a "thing" going here with a reasonable and educated crowd of critical mass interested in weighing in on this topic (puns intended) in this forum. Why pull the rug from under that inertia? Enuja, if you can get most of the people all moved over there and re-engaged on this topic, e-mail me or leave a message on my talk page that you’ve managed that trick. Greg L (my talk) 02:46, 8 November 2007 (UTC)

I think it would be OK to discuss the topic in a separate article and link to it from all over, because it affects all the articles on units of mass, the article on weight and the article on mass. However, it wouldn't really bug me to keep the discussion at the "weight" article and link there from the other articles either, so I'll support either of those options. But we must definitely discuss the proposed move at talk:Pound, talk:Weight and talk:Mass at least. —Preceding unsigned comment added by Slashme (talk • contribs) 18:50, 8 November 2007 (UTC)

• I’ve posted a notice on Talk:Weight that the discussion is ocurring here. I can do the same at the other venues. Greg L (my talk) 18:56, 8 November 2007 (UTC) P.S.: I’ve also posted at Talk:Mass and at Talk:Pound. Greg L (my talk) 22:29, 8 November 2007 (UTC)

• As regards whether or not “weight” appropriately means “force due to gravity” in the physical sciences, this issue has been (or should be) put to bed. The meaning of the term “weight” is abundantly clear in the physical sciences, as has been demonstrated above at Talk:Kilogram#Addressing more issues (in topic “Addressing 3.1”). It’s time to put that issue to bed and move on to deciding where is the best place for a proper, encyclopedic treatment of the subject. Greg L (my talk) 18:56, 8 November 2007 (UTC)

• To newcomers to this issue: So far, three people wouldn't mind seeing the Kilogram article’s Mass versus weight section moved to a new article titled the same. In the spirit of trying to expeditiously build a quick consensus, if you approve of this approach, please state as such. If not, please tell where you think it should be moved to (or other opinion). Greg L (my talk) 22:28, 8 November 2007 (UTC)

• • I am glad to see there is finally agreement to DO SOMETHING. Presently the article contains what could be at least 3 or 4 separate articles - (kilogram, issues with defining the kg & attempts to resolve, mass v weight, buoyancy). Of these, the first 2 are most relevant to a kilogram article -- however the issues with part is broken up by having the others intervening in the exposition--JimWae 20:36, 10 November 2007 (UTC)

Where should the "mass versus weight" issue be dealt with? It seems just obvious to me. Mass should be discussed in mass, and gravitation should be discussed on gravitation. Nobody would make weight a disambiguation page, right? So I think that the weight article should look like that: 1) A brief explaination of what weight means in physics, with a Main articles: gravitation, force notice; also a summary of apparent weight, and the buoyancy issue (AKA "does 1 kg of gold weigh more than 1 kg of feathers?"); 2) A brief explaination of what weight means in commerce and trade with a Main article: mass notice; 3) The reason why these concepts are often confused/used interchangeably in everyday life, and a clear distinction between the two, such as most of the Mass versus weight section here. Creating a new article for fear of an existing article being deteriorated, known as content forking, is not a very good idea. If done, the title of an article should be the one most likely to be used as the caption of a link to it, and in few places one would use the phrase mass versus weight other than for its own sake; a link caption such as in "The distinction between mass and weight is often etc." would be more likely. Note that "well-defined meaning of a word in physical sciences" doesn't mean "only correct usage for a word"; would you say that the use of "force" in Air Force, the use of "field" in a field in a database record, the use of "curl" in curls of hair are "wrong"? As for this article, it should contain no more than one or two paragraphs to summarize the weight article (with a link to it) to make that distinction clear and to define the kilogram-force, and it should discuss the issue of weight and buoyance only as relevant to the difficulty of obtaining precise measures of mass in air (the current Buoyancy and “conventional mass” sub-section could be more concise but it is otherwise OK). --Army1987 11:25, 11 November 2007 (UTC)

Very good points, Army 1987. All that really matters here is that it doesn't belong here. But Greg L's failure to understand the simple fact that a well-defined meaning in the mechanics branch of the physical sciences doesn't mean that a word cannot have an equally well-defined but very different meaning in another context such as the sale of goods is the root of the whole problem here. [Uhm… riiiiiight  Greg L (my talk) 20:26, 17 November 2007 (UTC)]

Like you said, discuss mass at mass. Discuss force at force. Discuss gravitation at gravitation and a whole host of related articles.

And discuss the kilogram at kilogram. Gene Nygaard 12:36, 16 November 2007 (UTC)

• [I confess I haven't read all of the above!] I agree that the "mass versus weight" issue should be explained once, and not split over multiple articles. I don't feel massively strongly about where it goes, but I'm wondering if the best place might be the weight article. This is because "weight" seems to be the problem term, and much of that article is already involved in trying to explain the two different usages. If we have a separate "mass versus weight" article then I'm wondering what we will do at "weight". Will we just explain the scientific meaning (i.e. force), and link to "mass versus weight" for the other meaning (i.e. mass)? If we explain both then we're automatically covering the same ground as "mass versus weight". Matt 03:56, 24 November 2007 (UTC) —Preceding unsigned comment added by 86.133.243.205 (talk)

What happened to moving mass-v-weight out of this article? Sorry, I don't have time, but I hope someone else does. Timb66 (talk) 11:28, 28 November 2007 (UTC)

• Done. There was a clear consensus to move it out of here but no clear consensus on where to move it to. There appeared to be two candidate locations being bandied about: Weight, and an all-new article titled “Mass versus weight”. I preferred the latter option because I don’t think Weight is any more logical of a location for the subject than is Mass, Kilogram, Pound (mass), or Weighing scale.

  To break the logjam, I created a new article, Mass versus weight. All articles that want to link to the subject can link to it there and won't have to link to either the top of Weight (or some other article), nor to a subsection within some article. Greg L (my talk) 03:23, 29 November 2007 (UTC)

Billiards on the Moon

• re the billiard balls on the moon. I am a complete layperson but i assume that gravity on earth would increase the friction so the decreased friction on the moon would mean that the balls broke and moved more swiftly, although falling into the pockets more slowly. Any experts there who can answer this question? 89.241.254.21 14:54, 9 November 2007 (UTC)

F<=uR is a good approximation for friction (u should be 'mu', the coefficient of friction). In this case, the maximum friction F on a billiard ball would be lower on the moon because the reaction R would be lower, in turn because the weight of the ball would be less. It should be noted that other effects (e.g. lack of drag due to lack of atmosphere) also come into play. In future, Wikipedia:Reference_desk may be able to answer your question. Hope this helps. Sheffield Steel^talk_stalk 16:32, 9 November 2007 (UTC)

The balls would also be much more inclined to rebound out of the pockets. A “Moon-grade” billiards table would probably have much enlarged pockets to compensate for this. Of course, all of these are subtleties that go far beyond the basic principal being conveyed. And technically, during a break shot, where the racked billiard balls are typically touching each other (or at most a few millimeters away from each other), the opportunity for meaningful differences in friction to come into play as the kinetic energy is distributed is effectively nonexistent (except for the speed of the incoming cue ball). The racked balls’ initial behavior would be very similar to that kinetic demo game where six steel balls hang from strings and “click-clack” back and forth. So, no, they would not ‘break with more swiftness’. Indeed though, they would do better on the Moon at retaining the finite kinetic energy (speed) the farther they got from their racked positions due to less rolling resistance; as Sheffield pointed out, the magnitude of this effect can be calculated. As for air friction, I was imagining the game being played on the Moon indoors in a shirt-sleeve environment (what do astronauts on a Moon base do in their spare time?). Greg L (my talk) 20:25, 9 November 2007 (UTC)

oops :-) Serves me right for answering the question in vacuo rather than reading the relevant part of the article and getting the context. Sheffield Steel^talk_stalk 20:51, 9 November 2007 (UTC)

legend of first picture

I almost had a stroke reading this:

Shown above is a computer-generated image of the International Prototype Kilogram (“IPK”). The IPK is the kilogram. It sits next to an inch-based ruler for scale.

an inch-based ruler? Right next to one of the cornerstones of the SI? Some people were drawn and quartered for less than that... We should try to find a better picture than something computer-generated. Toitoine 13:52, 11 November 2007 (UTC)

• Details of the creation of this image were all hashed over when the picture was nominated for Featured picture status. It didn’t make the cut. One of the objections was the inch-based ruler that you pointed out above. The CG image—as is most everything else in Wikipedia—was contributed by a volunteer (me, in this case). I made the image to replace an orphaned placeholder after the original photograph was deleted from Commons due to copyright issues. I happened to have had a solid model of the ruler on hand from a “real life” project. As the program I use (Ashlar Velum) is rather cumbersome when "painting" legends and numerals, I saved a lot of time in the creation of this image by recycling the ruler. I suppose that was my prerogative: to not spend an extra evening making a millimeter-based ruler. Thank you for the observation though.

  If you want to go beyond the “near-stroke” observation (and with respect to your “We should try to find…” sentence) and do something constructive to really help Wikipedia, you are welcome to find a nice, free-use image of the IPK and upload it to Wikipedia. You will find, however, that access is somewhat restricted to the BIPM’s vault in Sèvres. Alternatively, I would be thrilled if you volunteered to create a ruler from scratch (like I originally did) and "paint" all the thousandths-inch-thick, millimeter-pitch ink legends on it (complete with the numerals). Save it as IGS. I can then open your digital solid model, apply the textures and wood color maps, and ray-trace the image. I am sorry the current picture doesn’t meet your expectations. Being “drawn and quartered” for being responsible for this outrageous juxtaposition (the IPK along side an inch-based ruler) is certainly not something I look forward to! I do hope you approve of my tracking down the original blueprints used for specifying the machining of the four-angle chamfer on the two edges of the cylinder. I faithfully made the solid model per that blueprint. It also took me many, many hours to get the lighting right; reflective cylinders are tough to light. Next time, I’ll try to do even better. We can’t risk your having a stroke over shortcomings like this. Thanks for the help.

  You might also notify the other non-English versions of the Wikipedia Kilogram articles (these: be-x-old, cs, da, ka, sw, It, hu, mn, ja, sr, ay, bs, es, it, ru, and zh-yue), as well as GA Tech University because of this press release, and Physorg.com because of this press release—all of which are using this very same image. We can’t assume that the editors responsible for these image placements were all properly aware of this “inch-based ruler” issue when they made their individual decisions to also use the image. And we certainly can’t afford to have any readers suffering a forehead-hemorrhage after they realize the true nature of that ruler! Greg L (my talk) 03:24, 12 November 2007 (UTC)

Notes-section text size

Zginder: Regarding this edit using AutoWikiBrowser, according to Wikipedia:Footnotes, Resizing references: “Some editors prefer references to be in a smaller font size than the text in the body of the article.” There is no “preferred” method of doing this—even for expansive lists of notes.

The above-quoted article on {{reflist}} discusses a good rational why reduced-size text sometimes makes good sense: sometimes the “Notes”, or “References” sections are nothing but long lists of citations, such the references section for Psycho (1960 film). In citation-only References sections like this, all you get is a highlighted citation when you click on a footnote. Small text is adequate for this purpose. In other cases, like the Kilogram article, the notes section is truly a Notes section, where points are sometimes expand on (in addition to providing citations). Especially on some computer systems with high-res monitors, reduced-size text is too small for comfort so normal-size text in situations like this is the better option. Greg L (my talk) 21:52, 24 November 2007 (UTC)

Restoring to consensus version

Jimp: Regarding this edit, please see above sections (1, 2, 3, 4, 5, 6, 7, 8, 9, and 10) of this discussion page. As you will see as you skim through the above, very much discussion has transpired regarding the nature of mass vs. weight and its proper treatment here on Kilogram. A huge editing battle resulted in an enormous amount of effort to clear up a Wikiquette alert that arose from it all. The information you deleted was all included for one (supposedly) good reason or another. For instance, the discussion of the Pound (mass) was included because there is a (very) widespread belief that the kilogram is uniquely a unit of mass whereas the pound is a unit of weight. An expansive treatment of the subject of Mass versus weight was originally included in this article but eventually found a home with its very own article. What remains of the subject is now very limited, is the product of great effort and compromise, and mainly relies upon the link to the Mass versus weight article. The consensus is that the current, limited treatment is appropriate, encyclopedic, and balanced. Thank you by the way, for fixing the micro symbol template. Greg L (my talk) 07:15, 11 December 2007 (UTC)

While the language in the lead has seen a lot of back and forth editing to get to a consensus, consensus can always change. Jimp, your edits will probably be less likely to be reverted if you try to clarify language and organize the content instead of only deleting content (although sometimes a delete is needed!). Personally, I think that the conversion to pounds is important because it tells people who use pounds how much a kilogram weighs, and I do think people should know both that the kilogram is a unit of mass and that there are related and unrelated units of weight. If any user can come up with a more clear and concise way to say these things, I at least would grateful to that person. I don't think that the first section should be titled "the nature of mass"; I'd much prefer a top section titled something like "Common use" which had a smidge about mass and was a place for all of the important, hard to characterize stuff that should be early in the article. - Enuja (talk) 00:22, 12 December 2007 (UTC)

Avagadro Project

Is there a source to any part of the Avagadro Project section? I think that this information is much too detailed to omit a citation. NatePhysics (talk) 22:16, 11 December 2007 (UTC)

• I added the citations Nate. Much of the information in the Avogadro project section came from the Avogadro Project NPL Web site, which used to be much more expansive than it is now. About a month ago, NPL deleted the site and replaced it with a different URL that is much stripped down compared to the original. Hopefully, they will slowly add information to the new page until it is as informative as what it replaced. Greg L (my talk) 00:51, 13 December 2007 (UTC)

Proper venue

Mcgeachy: Regarding this edit (which greatly expanded upon the distinction between inertial mass versus gravitational mass), please see above sections (1, 2, 3, 4, 5, 6, 7, 8, 9, and 10) of this discussion page. As you will see as you skim through the above, very much discussion has transpired regarding the nature of mass vs. weight and its proper treatment here on Kilogram. An ensuing battle resulted in an enormous amount of effort to clear up a Wikiquette alert that arose from it all. The information you added was all originally here in an expanded treatment of the topic that had its own section titled Mass versus weight (historical version here). After the above-mentioned debate, the subject was moved out of this article and given its own Wikipedia article at Mass versus weight. What remains of the subject here at Kilogram is more limited and is the product of great effort and compromise. As you no doubt saw, the subject of inertial vs. gravitational mass (weight) is now briefly and appropriately covered in the section titled The nature of mass and, further, the section has a header in this form:

Main article: Mass versus weight

…which lets the reader know where to go for an expanded treatment of what is effectively a tangential topic. Only two days ago, another editor made this edit, which deleted all treatment of the topic of weight vs. mass here on Kilogram. Well, it’s clearly impossible to make all the people happy all the time and some sort of compromise must be struck between wholesale deletion of the subject and a much-expanded treatment. What now remains of the topic here at Kilogram (after being restored from the previous deletion) is covered with an appropriate level of detail for an article that is supposed to be about the kilogram after all.

A far better home for what you added clearly would be in Mass. I suggest you carefully read Mass and make your edits on the distinction of inertial mass versus gravitational mass there. In fact, the Mass article already has a section titled Inertial and gravitational mass, which, in turn, has three related subsections (Inertial mass, Gravitational mass, and Equivalence of inertial and gravitational masses). Further, the Mass article is currently flagged for a lack of citations and footnotes; it could use some professional cleanup. Greg L (my talk) 03:40, 14 December 2007 (UTC)

American vs. British spelling and punctuation

Slashme, regarding your recent edits, some “American vs. British” issues cropped up and made for an inconsistency. According to Wikipedia:Manual of Style, our official policy is that the spelling convention used by the first major contributors should be retained. The Kilogram article is written throughout with American spelling (kilogram instead of kilogramme, liter instead of litre) and further, has been using American punctuation conventions; specifically, it’s been using em-dashes set closed—like this—rather than set open with spaces. Note that according to Wikipedia’s own article on the em-dash Dash: ‘m’ dash…

“ According to most American sources (e.g., The Chicago Manual of Style) and to some British sources (e.g., The Oxford Guide to Style), an em-dash should always be set closed (not surrounded by spaces). ”

Most of your recent edits were good and I accept them (I debated whether underlining was warranted for “in comparison to its official copies” as I thought it an extremely important point that merited great emphasis). However, your changing of some em-dashes to a set-open style 1) betrays your habits of the South African/British punctuation style, and 2) you only changed some of the em-dashes, many others were left as is. Inconsistency within a single article isn’t good either. Please also take note of another common-sense policy from Wikipedia: Manual of Style: National varieties of English: (Consistency within articles):

“ An overriding principle is that style and formatting should be applied consistently throughout an article, unless there is a good reason to do otherwise, except in direct quotations, where the original text is generally preserved. ”

Greg L (my talk) 19:37, 14 December 2007 (UTC)

Avogadro Project, silicon sphere picture

An interesting development: Yesterday I e-mailed two groups working on the Avogadro Project and asked them for some free (uncopyrighted) pictures of the silicon sphere (hopefully a nice, quality picture like this one). Both responded this morning that they’re working on my request. Hopefully, both organizations will provide multiple pictures to choose from. Greg L (my talk) 21:20, 14 December 2007 (UTC)

• And… done. It took over a month (Christmas vacation and all). I got the photo and they agreed to a GNU license. I also had some e-mail exchanges with the project manager of Gravity Probe B to check some facts on “roundness.” Check it out here. Greg L (my talk) 06:02, 12 January 2008 (UTC)

Great work! --Slashme (talk) 09:19, 24 January 2008 (UTC)

Thanks. Greg L (my talk) 03:05, 5 February 2008 (UTC)

Anti-carbon bias in the article

>Carbon-12 Though not offering a practical realization <

Why exactly? In fact it would be splendid if the new kilogram prototype would be made of pure diamond, since diamonds are forever. As diamonds have a perfect crystal structure, the number of carbon atoms in it could be counted exactly. Diamond is also the hardest material and is noble, so mechanical wear and undesired reactions would become a non-issue. The next kilo should be a big artifical diamond! 82.131.210.162 (talk) 18:26, 9 January 2008 (UTC)

I wonder if there's a law against elemental discrimination ... :-) Thunderbird2 (talk) 18:33, 9 January 2008 (UTC)

• To anonymous author from Budapest Hungary: I commend you on your command of English.

  Well, I haven’t found a reputable, peer-reviewed science journal in which someone is proposing a defining mass prototype of the kilogram made of diamond. Has anyone else? Regardless, you’re right; in an ideal world, diamond would be a perfect realization. The operative word in “practical realization” however, is “practical”. Diamond as a “technical realization,” yes. A “practical realization,” no. And I thought the 40 kilograms of platinum for the first lot of prototypes was expensive.

  It seems to me that the trouble with diamond is that it's a bit like that cure-all engineering material “unobtainium”: short of mining a white dwarf star, it’s rather hard to come by; especially in multi-kilogram lots. The largest clear diamond ever discovered had a mass of 621 g in its rough form. In over a century of digging with modern earth-moving equipment, no clear diamond bigger has yet been discovered. The biggest single cut diamond they could get out of it that was free of cleavage lines, strain, and defects, the Great Star of Africa, had a mass of only 106 grams. In 1985, the “Unnamed Brown” diamond (755 carats or 151 g) was discovered and was later faceted as the 545.67 carats (109.13 g) Golden Jubilee diamond. But, as you can see in this picture, the Golden Jubilee diamond’s brown color means it has a lot of extraneous dopants that severely affects its weight and would make atom-counting approaches nearly impossible.

  With regard to your “[t]he next kilo should be a big artificial diamond!”, it also seems to me that man-made diamonds have some deal-breaking shortcomings. The biggest man-made diamonds are only about a half gram. Plus, man-made diamonds are yellow because the entrained nitrogen atoms in them are clustered together in aggregates large enough to disrupt light. I strongly suspect this non-homogeneous distribution of nitrogen is the underlying reason why man-made diamonds are softer and more brittle than natural diamonds: it’s presence strains the crystal lattice. Further, the presence of nitrogen means that you just can’t “count” atoms; once again, you are in the business of quantifying the nitrogen and characterizing its isotopic composition in order to compensate for its effect. Even ignoring nitrogen, isotopic characterization would still have to be done if you want to count atoms because no one can separate carbon-12 to a purity of eight or nine 9s. And who knows how the presence of exposed nitrogen clusters at the surface of a man-made diamond might affect its long-term mass stability?

  If you believe the article is “biased,” something that would be very helpful would be for you to track down an article published in a reputable, peer-reviewed science journal in which someone is proposing to make a defining kilogram mass prototype out of diamond. It would be an intolerable situation for an on-line encyclopedia to be biased. Such an important factual error—if it exists—should be corrected. Greg L (my talk) 19:11, 12 January 2008 (UTC)

• P.S. Having said all that, I think there still might be a role for diamond: serving as long-term mass-stability artifact. Instead of trying to count atoms and instead of trying to use diamond as a defining mass prototype, an assembly of small, natural diamonds might be useful, in my opinion, to help establish the long-term stability of future single-pan scales (like the watt balance), or mass artifacts (like the IPK and silicon spheres from the Avogadro project).

  The IPK may have drifted 1000 µg over the last 50 years and there is absolutely no way of knowing whether that actually occurred or not. Further, even cutting-edge single-pan scales like the watt balance might suffer from systematic errors. Right now, the NIST’s watt balance is demonstrating fairly low uncertainty but I believe this term is best interpreted as “mid-term repeatability” because there are now differences in published values between the Avogadro project and watt balance experiments. Not too long ago, the NIST discovered that some epoxy for reinforcing the wires in a coil they built in 2001 had entrained pockets of uncured epoxy. The “liquid” epoxy polarized in the presence of magnetic fields and was interfering with their measurements. What do you do if you discover another systematic error in the future and you not only improve your short-term uncertainty after you fix it, but discover that new measurements seem to differ by 5–10 ppb from those made several years earlier? Is your machine different or was there a foul-up somewhere in the cleaning or stability of K4? How do you compare measurements this year in the NIST’s watt balance to ones made six years from now in a the UK’s watt balance? The Pt10Ir prototypes are drifting at least 0.5 µg/year, and some are undoubtedly drifting much more than this. Thus, performance comparisons bewteen single-pan scales on different continents can only be accurately (~2 ppb) done within about a few months of each other. Proving relative performance across time at a level of even 10 ppb per decade is impossible right now.

  What might be useful for future generations is to collect about 250–500, ten-to-twenty-carat (2–4 gram) natural diamonds. This wouldn’t be quite as expensive as it sounds because you wouldn’t cut them into classic gem shapes, which wastes a lot of material, and would instead cut and polish them close to their natural octahedral shape. It also wouldn’t matter if they had ugly inclusions so long as they were deep; you only need “flawless gem quality” near the surface. I don’t know all the details of diamond and why it should be more stable than Pt10Ir, but they’re single crystals (very good because they won’t allow anything else into their lattice structure after they’re formed), non-catalyzing (damn good when VOCs deposit on them or if you’re using hydrocarbon-based cleaning solvents like ether and ethanol), non-metallic (damn good because they don’t absorb hydrogen or mercury), harder than hell (good), won’t loose even a molecule-thick layer to oxidation (CO₂) unless heated to high temperatures (good), and they’ve survived eons being thrust up from 100 km deep in the Earth imbedded in blazing hot rock and don’t look half bad after the trip. There wouldn’t be much left of the IPK after such a trip except, maybe, a peanut-size nugget and some platinum dust on the bottom of your pan.

  Because of all their surface area, a large quantity of diamonds would be somewhat of a pain to clean but there are liquid-solvent cleaning processes in the semiconductor industry that could be adopted that might do the trick. This collection of diamonds could be compared to the IPK and assigned an offset value and comparative date (similar to star positions, which were assigned “2000.0” coordinates in star catalogs). A 250-piece “diamond kilo” might be designated “1 kg + 452 µg, 2009.3”. This should produce a rock-stable mass artifact to compare against. Even if physicists reconcile the differing values of a carbon-12-based definition of the Avogadro constant (which traces straight back to the IPK) vs. an Avogadro project artifact vs. the watt balance, no one to my knowledge has advanced a plan for establishing long-term mass or mass-measurement stability that doesn’t rely on spectacularly complex engineering analysis arguments as to why, for instance, forces and geometry and physcis in something like the watt balance precisely cancel and therefore must be zero. It would be reassuring to be able to drag in the ol’ box of “K_diamond 2009.3” and double check. I guess of course, this is what they thought there were accomplishing in 1879 with Pt-10Ir: rock-stable, long-term mass. Didn’t get it though. Unless some of those scientists managed to live until 1948, they never had a clue of the instability in their lifetimes. Greg L (my talk) 22:52, 13 January 2008 (UTC)

Carbon, continued

Long story short: Find good refs of a serious proposal to use carbon as the next IPK or it's WP:OR.

To Greg L: Check out synthetic diamond. Things have changed somewhat since you last surveyed the field. Sure, they're nowhere near a kilogram yet, but the colour and clarity are now better than mined diamonds. --Slashme (talk) 05:52, 17 January 2008 (UTC)

• Slashme. Thanks for the link. I hadn't noticed the synthetic diamond article. From what I read there, the colorless diamonds produced by Apollo Diamond using chemical vapor deposition (CVD) generates nanocrystalline diamonds that are only 30%–75% the hardness of single-crystal diamond. Those zillions of crystal boundaries are certainly not a good thing, and my bias is that they’re likely a bad thing. Man-made, compression-formed (single-crystal) diamonds still have nitrogen and are yellow (and max-out at about 7 grams). It appears that given the current state of the art, an agglomeration of synthetic diamonds still would be unsuitable to serve as a long-term mass stability artifact. It appears though that they’re making rapid progress though! Greg L (my talk) 01:23, 18 January 2008 (UTC)

Check out Chemical vapor deposition of diamond:

The Carnegie Institute's Geophysical Laboratory can produce 10 carat (2 g) single-crystal diamonds rapidly (28 nm/s) by CVD, as well as colorless single-crystal diamonds. Growth of colorless diamonds up to 60 g (300 carats) is believed achievable using their method

Also see Apollo Diamond:

produces nearly flawless single crystal diamond wafers and crystals for the optoelectronics, nanotechnology, and consumer gem markets.

But the fact remains that until someone proposes using diamonds, in a reputable secondary source, it remains OR and should stay out of the article. --Slashme (talk) 07:28, 18 January 2008 (UTC)

• Interesting. It appears synthetic has quite some promise as a long-term mass-stability artifact. Regarding OR (original research), I completely agree; that’s why I began and concluded my initial response with a statement about the need for a peer-reviewed scientific article for the subject to be introduced into the article. My postscripted thoughts regarding diamond are nothing but hypothetical musings intended to provoke critical debate for fun and intellectual stimulation; I would hope that nothing I wrote suggested otherwise and I assume that your pointing out the latest virtues of man-made diamonds was offered in the same spirit. Greg L (my talk) 21:27, 18 January 2008 (UTC)

Ditto: My comments on the advantages of synthetic diamonds were academic in nature, and my repeated references to OR were to avoid being misinterpreted. --Slashme (talk) 13:25, 21 January 2008 (UTC)

water volume vs kg

In the article it is stated that the IPK was found to deviate from 1 dm³ of water by 25 ppm. If they can determine this number that accurately, wouldn't this provide a simple way to determine whether the IPK's drift relative to its copies is due to its own mass drifting or due to an average drift of the herd of copies? --Slashme (talk) 09:16, 24 January 2008 (UTC)

I've wondered the same thing. My first major Wikipedia contribution was to Vienna Standard Mean Ocean Water so I can shed some light on this one. VSMOW has a peak density of 999.97495 kg/m³ at 3.984 °C, which is a measured precision of only 10 parts in 10⁹ (maybe only 50 parts as the CRSU isn’t specified). The bigger trouble is that isotopic composition of VSMOW wasn't established until 1968. A hundred years ago, scientists used water of uncontrolled isotopic composition. Further, its likely they didn't even start with ocean water (why hassle with all those solids). If the scientists back then had been using spring or river water (or similar water that had recently fallen as rain), it would have been enriched in the more volatile, lighter-mass isotopes. The long-term (50–100 year) 1000 µg uncertainty in the mass of the IPK in concise form relative to the density of water appears as 999.97495(100) kg/m³, thus the “4” could have been one count different as little as only 50 years ago.

Having worked with SF₆ density monitoring equipment (equipment designed to detect slow leaks in other equipment) and hydrogen-powered fuel cells (hydroge is tough to seal), one of my engineering specialties is ultra-tight seals. Bell jars don’t impress me much. I personally think it is more likely that the entire world-wide ensemble of prototypes have been increasing in mass—the least protected ones more so than others. Note that K20 (the U.S.’s primary standard that is most protected and least used) wasn't plotted in the stability graph but it would have been exactly on the zero line with the IPK. Few countries have two [three] Pt-10Ir prototypes like the U.S. so the fact that our primary national standard was flatlined relative to the IPK is a strong clue as to what's going on in my book. I think the prototypes that spent the most time outside of their bell jars gained the most. Those that were best protected and spent the most time under their bell jars (like the IPK and K20) gained the least. All gained something, I figure. Greg L (my talk) 06:24, 29 January 2008 (UTC)

OK, that makes sense. --Slashme (talk) 10:17, 29 January 2008 (UTC)

Coal and atmospheric mercury

Mass drift over time of national prototypes K21–K40, plus two of the IPK’s sister replicas: K8(41) and K32. All mass changes are relative to the IPK.

One theory advanced by those who have dedicated their careers to the international standard of mass is that platinum, which has great affinity for mercury, is absorbing atmospheric mercury. This theory (for which there is currently no way to prove or disprove it), holds that all the world’s prototypes are gaining mass—just that some are gaining faster than others.

• The recent addition of the picture of K48 to this article and the caption regarding K48’s rapid mass gain got me doing a bit of exploration. K48’s mass gain works out to a rate of 78 µg per century. On the chart of mass changes, it would be slightly off the scale had its rate of mass gain gone on for a full hundred years. OK, the question is: Why? If there is a connection to absorption of mercury, does Denmark have a lot of it?

  I note that the Danish National Metrology Institute is way out on the far eastern part of Denmark, downwind of many major cities like Randers, Viborg, Holsebro, Herning, Silkeborn, Arhus, and Ringkøbing. I also note that Sweden is complaining about all the coal-fired pollution being “exported” from Denmark. Denmark on the other hand, is complaining about Sweden’s nuclear reactors and how they might endanger nearby countries. Note that roughly half the world’s atmospheric mercury comes from world-wide energy production, particularly coal. Note too, that Sweden’s kilogram prototype, K40, has gained only 2 µg (relative to the IPK) in 100 years. Note too that the IPK is stored in France, which has 90% of its electrical power produced by nuclear reactors (not coal). Thus, the two countries known for nuclear power posses kilogram prototypes that have gained little over the last century whereas the one stored in a country noted for exporting coal-produced atmospheric pollution has rapidly gained mass.

  I find that just darn fascinating. Don’t you? I wish I had more time to study this one and add more data points to it. Anyway, this observation supports the hypothesis that all the prototypes are gaining mass and the phenomenon is due to mercury absorption. Greg L (my talk) 06:52, 8 February 2008 (UTC)

That's a very interesting hypothesis! How many ppb mercury would there have to be in the atmosphere to do that, I wonder? It looks like the kind of thing that could be quite easily subjected to a reality check. --Slashme (talk) 07:50, 8 February 2008 (UTC)

• From a quick Google search, it appears there is “gaseous elemental mercury” (GEM), and “reactive gaseous mercury” (RGM). I saw that a study in urban Detroit measured GEM at 2.2 ±1.3 ng/m³ and RGM at 17.7 ±28.9 pg/m³. This site reports “total gaseous mercury” (TGM) concentrations in Beijing of around 10 ng/m³. As this is much greater than in Detroit, my hunch is that a Pt-10Ir kilogram prototype wouldn’t have any stability whatsoever in Beijing.

  Spain (K24) is also interesting. Note K24’s upturn leading into the 1988–1992 periodic verification. According to CountryStudies, “Spain is poor in energy resources, with the exception of coal.” Further, they write that higher oil prices have spurred Spanish coal production. Spain’s annual production of coal and lignite in in the early 1970s amounted to about 13 million tons. By the mid-1980s, the industry’s annual production had trippled to 38 million tons. France (the IPK) is almost all nuclear and is on the upwind coast of the eurasian continent. Spain has always been dependent upon coal and oil but transitioned even more heavily into coal in the ’70s. And just see what K24’s mass gain trend looks like. Double-interesting.

  I’m going to be keeping my eyes peeled for a by-country breakdown of electrical generation by fuel source, or (better yet) coal consumption per country. Unfortunately, the CIA factbook (the lock {} means it’s a secure, “https” site) only enumerates natural gas and oil imports. It also only mentions coal in a general sense in that it is one of Spain’s natural resources; it doesn’t cite how much is used. Greg L (my talk) 18:31, 8 February 2008 (UTC)

unclear sentence

I'm having trouble understanding this sentence:

Note that the redefinition of the meter in terms of a duration of one second reduced the uncertainty in the wavelength of the laser light.

Maybe someone who understands what the intention is here can re-write it to make it clearer? --Slashme (talk) 09:29, 24 January 2008 (UTC)

I deleted it as it wasn't worth the wind. My point was that we had gone from a definition of the meter based on wavelengths of krypton-86 to a delineation based on a HeNe laser. Thus, the meter is still measured out in terms of light wavelengths. I was trying to almost parenthetically point out that at least what was accomplished via the new definition of the meter (in terms of light time-of-flight) was a 5X reduction in the uncertainty in the measured wavelength of HeNe laser light and thus, a reduction in the uncertainty in the length of the meter. It's a nuance of the meter that doesn't have anything directly to do with the kilogram. Given that you didn't understand the sentence (and you've been studying this article with great intent), the near-parenthetical, off-topic aside wasn't worth the effort to read and understand it. Greg L (my talk) 06:36, 29 January 2008 (UTC)

Ah, OK. --Slashme (talk) 10:18, 29 January 2008 (UTC)

Ion deposition

Well, why not use Be, Al, or Mn?? They're all naturally much harder than gold, especially Be, and while oxide coated, aren't nearly as badly coated as Bi. SBHarris 06:11, 1 February 2008 (UTC)

Interesting. I don’t know but I can guess. At the time I was faithfully memorializing what is in the CGPM report, I had the very same question you did and (very) briefly looked for other elements that have only one naturally occurring isotope. I didn’t find any and concluded they were pretty rare. I believe your point is that you’ve identified three other elements that have only one naturally occurring isotope. One of the things I made for myself when I was working in the fuel cell industry is a pocket periodic chart for M.E.s. It skips over all the “electron orbital” stuff that chemists love (*yawn*) and zeroes-in on the sort of issues an M.E. in fuel-cell R&D needs: bulk density, melting point, molecular weight, and electromotive potential (so you can avoid galvanic corrosion). I just dug both it and my jeweler’s loupe out of my pocket (my eyes don’t focus that close anymore) and here’s what my chart says:

Electromotive potential

(Hydrogen = ±0.000) 

Gold, (MW 197) = +1.401

Bismuth (MW 209) = +0.2

Manganese (MW 55) = –1.185

Aluminum (MW 27) = –1.662

Beryllium (MW 9) = –1.847

As you can see, the three elements you cited are rather easily oxidized. That’s not the whole story with oxidation; for instance, aluminum develops a coherent oxide (similar lattice spacing to the underlying metal) so it doesn’t spall off like iron and is therefore passivating (protective). However, even the briefest exposure to air would instantly form an oxide layer on aluminum. I believe the same would go for both Mn and Be given their electromotive potentials.

My hunch is that the biggest virtue of bismuth is that it has a molecular weight even greater than gold. Thus, the scientists got more “bang for the buck” mass-wise while neutralizing all those ions with their modest (but exquisitely measured) electrical current. In fact, of all the chemical elements, gold and bismuth are the ones with the two very highest atomic masses that have only one stable, naturally occurring isotope. That can’t possibly be an accident and must be by design. Plus, bismuth isn't as electronegative relative to oxygen (which is +1.229 V relative to hydrogen) and it’s cheap. It is clearly the element to experiment with if you don’t want to endure the expense of gold. That’s my take anyway on why they chose bismuth. Greg L (my talk) 01:01, 3 February 2008 (UTC)

P.S. I found this on Wikipedia: Isotope table (complete), which makes it very easy to find other single-isotope, non-radioactive chemical elements. Wikipedia has a lot of information; it’s really quite an amazing thing. Beyond the elements you cited, I also found eleven [nine] more: ⁷²As, ⁸⁵Rb (highly reactive), ⁹³Nb, ⁸⁹Y, ¹²⁷I , ¹³³Cs (highly reactive), ¹⁴¹Pr, ¹⁵⁹Tb, ¹⁶⁵Ho, ¹⁶⁹Tm, and ¹⁸¹Ta.

For ultra-accurate work, I would think that those elements that are strip-mined and which have atomic masses in the range of roughly 72 u to around 165 u would be contaminated with small amounts of artificially created radioisotopes from atomic bomb experiments. An estimated 5000 kg of plutonium was released into the atmosphere by nuclear weapons tests. Since atomic bombs are about 25% efficient, I would estimate that about 1700 kg of fission byproducts were released into the air. The Pu-239 nucleus rarely splits down the middle. Instead both the atomic mass and atomic numbers of the fission fragments have a Gaussian distributions centered around two means (one around 95 u and the other at 135 u). Bismuth (209 u) however, is so close to the starting weight of Pu-239 that I would expect very little Bi-207 or Bi-208 (the two long-lived radioisotopes) would have ever been created in the first place. The same goes for gold—even if it’s strip-mined. Greg L (my talk) 02:42, 3 February 2008 (UTC)

Both tantalum and rubidium contains two naturally occurring isotopes. ⁸⁵Rb is radioactive and ^181mTa is predicted to be slightly radioactive.--V1adis1av (talk) 23:38, 3 February 2008 (UTC)

• Yeah, you’re right V1adis1av (and SBHarris, below). I was referring to Web Elements at the time and must’ve got just flat sloppy as I didn’t winnow out those two.

This is two separate questions, of course. It's not enough that an element only have one stable isotope. It also must have no radioisotopes with half-lives larger than about 100 million years, so you don't measure THEM. K-40, Rb-87, Ta-181m and so on cause problems only in that way. There are at least a dozen more elements which have multiple stable isotopes, but are radioactive anyway, due to even more long-lived ones. In caesium's case, there is only one stable isotope, and I wonder if the radioactive isotope is in quantity large enough to matter anyway. In fact, I was a bit shocked to find that of the 340 or so naturally-occuring nuclides on Earth, less than 80% are stable. Anyway, the extra 11 elements you found indeed all have only one stable isotope (my provisional number is 16 for this property, and I'm going to add this to the isotope article so correct if wrong), but for several of them, it doesn't matter due to the long lived radioisotope contamination. SBHarris 04:28, 13 February 2008 (UTC)

• Yes, well, obviously to avoid fission products we want to use deep-mined minerals for this purpose, but that's not hard. I was aware of the others you mention, but they're all quite reactive, with the exception of Ta. And that's effectively out for an interesting reason: Ta-180m is so long lived it might as well be stable, so Ta, which otherwise has excellent corrosion properties, is an isotopic mix of 181-Ta and 180-Ta. I suppose that leaves us with Au. I was merely pointing out that the thinness of the passivating oxide on the others might make one of them attractive with respect to Bi, even with the other considerations of weight per reducing current and electromotive potential that you mention. SBHarris 09:52, 3 February 2008 (UTC)

• Well, not “all” are “quite reactive.” Niobium (electromotive potential: –1.099 V) was used to coat the fused quartz gyroscopes on Gravity Probe B and no one worried about exposing those to room-temperature air because its oxide is highly passivating. Also, given that bismuth’s electromotive potential is +0.2 V, and the fact that the researchers chose it for ion deposition mass-prototype experiments, it seems to me that its oxide should be every bit as thin and passivating as Be, Al, and Mn—probably more so. Still, your question prompted exploration that reveals how bismuth and gold were clearly the only two logical choices for very important reasons. And the Kilogram article is better off for that interesting exercise. Greg L (my talk) 20:07, 3 February 2008 (UTC)

• P.S. It’s hard to find much on the Internet regarding the oxidation of bismuth, but…

  Thinking that an electromotive potential of +0.2 V should be a pretty slow rate of oxidation, I found this Google search, which produces a hit (third one down) that gives the following “Google book” quote: “Bismuth oxidizes slowly when exposed to the air at ordinary temperatures, becoming covered with a brownish film of suboxide.” Accordingly, I’ve changed the text in the Kilogram article to reflect this “slow” aspect so as to not mislead anyone that bismuth has an unusual propensity for oxidation. The old text, which said “readily” oxidizes, was in the context of long-term (hundreds of years of exquisite stability) with mass-prototypes and was in contrast to gold, which doesn’t oxidize whatsoever at room temperature. Greg L (my talk) 20:31, 3 February 2008 (UTC)

Well, bismuth's oxide is much more noticable than the oxides of aluminum or beryllium. As a long time element collector I can tell you that it's just about impossible to keep bismuth samples nice and silver in air. Quite soon they turn yellowish and (worse still) the yellow isn't uniform, but takes on a number of interesting irridescent hues ranging from reddish to bluish, meaning that the oxide is not only thick enough to cause optical interference at visible wavelenths (as on a CD surface)-- which means it's at least 100 nm and up-- but also that the thickness varies over different areas of the metal. You'll never see anything like that with Be or Al. I don't quite know what's going on, but the visibility of it is enough to cause one to be taken aback. SBHarris 03:59, 5 February 2008 (UTC)

That’s interesting. May I assume that your pieces were relatively pure bismuth and that what you saw appears like this picture? *I wouldn’t mind having one of those.* I’ve seen the same sort of business on a batch of 17-7 PH stainless springs that were heat treated. I even had their surfaces analyzed using auger energy-dispersive X-ray spectroscopy in an SEM on the theory that maybe some carbides were involved. But no, the colors were all due to various oxide stoichiometries (double oxide = blue, brown = single, etc.) and—presumably—thicknesses. I think they just didn’t keep a sufficiently reducing atmosphere for that particular batch.

But here’s a conjecture: Check out this picture at Web Elements. It too depicts that colorful crystal form of bismuth but it also has some pieces of heavy-gauge wire that don’t display the “peacock-type” coloration. Somehow, it just looks like those wire pieces never would put on such a color display and might only just slowly develop a “brownish film” like the book describes. (That’s that “human intuition” that Mr. Spock would raise an eyebrow over.) Bismuth is right on the hair edge of being a metaloid and is in the nitrogen column. At +0.2 V, the bismuth should be talking to the oxygen in a cosmopolitan French accent, saying “No no. Do it doucement. Do it… slowly.” Do you suppose that the bismuth crystals might have terraces at the crystal lattice level and this somehow interacts with the oxides to produce the wild coloration? If bismuth really oxidizes that thickly, you’d think the researchers would have to rush to get their mass measurements. That certainly could be the case but I would expect they wouldn’t have chosen an element that required them to suffer with such a hassle.

It would be nice if someone weighed in here regarding bismuth oxidation and why the crystals have their wild coloration. Is the peacock coloration an oxide-thickness phenomenon or is it due to nano-level surface topology of the crystals (or a combination of the two)? If one polishes the crystals to remove the coloration, will the colors come back with time, or will the surface just eventually turn brown? Will the oxide on bismuth get thicker than 2–3 nm? Will it get to 2–3 nm slower than aluminum does? Greg L (my talk) 23:27, 5 February 2008 (UTC)

Somthing amusing to share

This news alert, International Prototype Kilogram Losing Weight: The Untold Story, is presented for your reading pleasure. Greg L (my talk) 20:39, 10 February 2008 (UTC)

P.S. There wasn’t a good, encyclopedic place to shoehorn this piece of trivia into, but I found it somewhat interesting—though certainly not “amusing”—and thought I’d share it: The NIST watt balance can typically “see” any 7.0+ earthquake anywhere in the world and picked up the 6.4 earthquake yesterday morning in Sonoro Mexico (which my mother, vacationing in Yuma Arizona e-mailed me about as they felt it and it made their chandelier swing). The NIST watt balance was affected by the 2004 Indonesian 9.2 earthquake for about four hours. Greg L (my talk) 17:48, 14 February 2008 (UTC)

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