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Can someone please explain the units and use of parentheses used in this equation from the article: 1 u = 1.660538782(83)×10−27 kg = 931.494027(23) MeV/c² The article is supposed to be accessible and I don't think this is. 139.133.7.37 ( talk) 12:25, 8 November 2008 (UTC)
In biology, the Dalton is often used in this way: "Only proteins smaller than [...]KDa can pass through this channel/pore." Since it is a unit of mass, isn't this strange? Are mass and size correlated in proteins? Since proteins can fold in many different ways, I would think that some proteins of a certain mass would and others would not fit through a channel/pore. Anyone?
Also the mass of any molecule can be converted in its number of protons + electrons, eg 1kDa is roughly 1000 protons and neutrons, and that is probably a good proxy for how large the protein will look like. I have read somewhere that after a 1MDa proteins don't even diffuse any more. — Preceding unsigned comment added by 188.223.9.243 ( talk) 23:43, 30 June 2011 (UTC)
Why did they choose the AMU convention of 1/12 of C12 rather than the original standard with 1/16 016?
How come only biological sciences use the Dalton unit? In chemistry there is rarely a unit. The header in a table of molecular weights would be labelled 'mw' or 'molecular weight' with no unit. Just a guess, but it may be because, when talking about large molecular weights, 'kilo (no unit)' sounds kind of stupid.
Physicists have the opposite problem - small values rather than large values. When they talk about mass deficiency rather than binding energy, it might well be appropriate to use mDa or μDa rather than milli or micro atomic mass units. Martinvl ( talk) 18:56, 24 April 2012 (UTC)
How do you change Atonic mass into pounds?
I removed the following paragraph; I think it's overly simplistic and illustrates a principle of college algebra rather than of atomic masses. It is certainly not relevant to the amu unit. It also uses the term "relative atomic mass" in a strange way and. AxelBoldt 16:44, 9 Oct 2004 (UTC)
A simple calculation may be used to calculate the relative atomic mass of the sample. This is demonstrated in the following example.
Ion | Relative Mass | Percentage Abundance |
11C+ | 11 | 70% |
13C+ | 13 | 30% |
Therefore, the relative atomic mass of the Carbon sample is:
[this is not the true atomic mass of carbon, it is merely illustrative]
The number on the page for u didn't agree exactly with the CODATA value referenced at the bottom. CODATA is state of the art, I have changed it to the CODATA value.
Is it 1/12 of a C12 nucleus or atom? I can't remember my high school physics, and some sites say it's "nucleus" and a few say it's "atom".
It's both, the mass of the atom is the mass of the nucleus, since the mass of the electron is negligible. Mchmike 03:19, 19 October 2006 (UTC)
No, it's not negligible. The electrons weigh something. In order to be accurate, the 1/12 must be defined as something, and the pure number 1/12 is infinitely percise, hence it must be 1/12 of either the nucleus or atom. 65.185.93.86 ( talk) 21:31, 22 May 2008 (UTC)
No. It is definitely the atom. The mass of the electron is about 1/2000 of the mass of a nucleon, much larger than the accuracy to which nuclear masses can be determined. It is negligible for some purposes, but not for all.
I read in two college texts that the absolute mass of the atomic mass unit is 1.66054E-24 grams. Wouldn't that make kilograms .00166054E-27? RAW 18:54, 24 April 2007 (UTC)
Perhaps this article could be edited to more obviously show the relation between Daltons and the molecular mass in g/mol? Roddyboy 03:28, 15 May 2007 (UTC)
The most common use of 'Daltons' is as a synonym for g/mol. When someone talks about a 254 kDa protein, they mean it has a molecular mass of 254,000 g/mol. I think this article needs to make this clear. 27.54.43.66 ( talk) 03:46, 28 May 2011 (UTC)
The author is correct when writing that the molecular mass of water is 18.0106 g/g-mol. However, in some industries (especially petroleum refining) in the United States (perhaps elsewhere), lb/lb-mol is the preferred term. Furthermore, there it is called molecular weight. As one could see by inspection, 1 g/g-mol = 1 lb/lb-mol. —Preceding unsigned comment added by 69.42.7.158 ( talk) 02:09, 11 August 2008 (UTC)
Why is only 1/12th of the carbon atom taken for amu? Why not of any other element? —Preceding unsigned comment added by 202.125.143.73 ( talk) 16:48, 21 August 2008 (UTC)
This is because Ar(H) = 1/12 of Ar( carbon-12) = 1. Remember that atomic weight (Ar) is a ratio. It is the molar mass (M) = Ar * Mu, where Mu is the molar mass constant, 1 gram/mole. Thus, M(H) = 1 g/mole = 1 amu. -- Bsodmike ( talk) 20:36, 18 July 2009 (UTC)
Sorry, referring maybe I am being a bit tired/dense, where does it say that the preferred usage for large or small values is Dalton? It says it is "often used" sure, but the text is suggesting it is somehow preferred? ( diff in question) User A1 ( talk) 21:54, 11 August 2010 (UTC)
My understanding is that both usages are equally acceptable. There is a definite preference among biochemists, molecular biologists and polymer scientists for the name "dalton", simply because they work in kilodaltons. Chemists, who tend to work in the range 1–1000 Da, usually ignore the unit or use g/mol (which is numerically equivalent). I've never seen "millidalton" used in practice, but it's not incorrect and it might catch on in the future. It's not a big practical issue, and so we shouldn't give it WP:UNDUE attention. Physchim62 (talk) 18:13, 12 August 2010 (UTC)
You guys may be interested in the following:
"A suggestion has been made in the CCU (communicated to C2 through Brian Petley), that the time has come to replace the name and symbol of the unified atomic mass unit, u, with dalton, Da. The grounds are that the current name is a mouthful and the need to emphasize the concept of "unified" is long gone. The dalton is widely used in chemical mass spectrometry community (e.g. bio-chemistry). Its use will also bring the polymer chemists into the SI community. There is possible confusion with the astronomical unit ua, and people want to use u or U to denote the unit one. There was considerable comment on this matter from many of the SUNAMCO members. In the short term the proposed change simply endorses the present reality that both the atomic mass unit and Dalton are in use."
It does seem to me that the powers that be (BIPM, IUPAC, IUPAP) are moving towards adopting Dalton more widely, but not doing anything to deprecate the AMU (they rarely deprecate any unit). I hope that helps. Lightmouse ( talk) 20:44, 13 August 2010 (UTC)
Be careful here. The "amu" is clearly deprecated (in 1961). The "u": maybe, maybe not. Small note: MilliDalton is in fact in common usage as some googling has shown. It's use arises from differences between masses with modern, highly accurate measurements.-- Nick Y. ( talk) 07:21, 17 August 2010 (UTC)
No consensus to move. Vegaswikian ( talk) 18:19, 30 August 2010 (UTC)
Atomic mass unit → Dalton (unit) — This is one of the earliest articles in Wikipedia (2002). The article "Dalton (unit)" had a short life in 2005 before being merged with this article on grounds that "It is often used in biochemistry and molecular biology although it was never approved by the Conférence Général des Poids et Mesures CGPM". Since then a number of things have happened (referenced in article):
In addition, the University of Oxford Style Guide for Life Sciences listed the dalton as an allowable unit (along with SI), but did not mention the unified atomic mass unit. This suggests to me that that we should at least be considering moving the text of this article to the article "Dalton (unit)". My assessment is that since the two articles have been merged, there has been a drift towards using the dalton in preference to the unified atomic mass unit and that the split in the literature is now 51% to 49%. (I am not going to justify these figures). Martinvl ( talk) 19:42, 23 August 2010 (UTC)
I have made a number of changes to the initial rewrite. Firstly I have rewritten the lede so that it only discusses the atomic mass unit without mentioning its relationship to the mole. The section, formerly called "Definition and Measurement" needs considerable rework. I have renamed it "Relationship to the mole" as that is what the content appears to be. Thuis section could well be expanded to show how it is used in the world of chemistry. The content certainly has nothing to do with measurement as it can be measured by any number of different methods. A similar section could be used to show how it is used in the world of physics, looking at Mass deficiency and the like.
I also think that the History section needs considerable expansion, showing how the difference definitions were brought together and why it is called the unified atomic mass number. Martinvl ( talk) 19:56, 25 August 2010 (UTC)
We should be aware that a wiki article's inertia is a lot less than that of a standards body. Also, we should not try to pre-emptively supply information. Let us worry about future hurdles in the future. We all seem to be better at writing talk pages than articles, myself included. User A1 ( talk) 15:13, 26 August 2010 (UTC)
The conversion factor between daltons and kilograms has a name, it's called the atomic mass constant: I find it remarkable that the article doesn't mention this (because it's been removed). Nor does the article give any information about how the value of this conversion factor is calculated: the equation mu = Mu/NA (referenced to the CODATA paper) needs to be reinstated, or readers are left with the impression that you can weigh a carbon atom. Physchim62 (talk) 13:32, 27 August 2010 (UTC)
I flagged this edit [4] as improper synthesis for the reasons outlined in this RfC: RfC:_Is_Kendrick_unit_original_research. -- Kkmurray ( talk) 17:26, 28 October 2010 (UTC)
I have modified the unfobox to show the dalton as an alternative to the amu, because firstly, it is just that and secondly, the article "Dalton (unit)" redirects to this artcile. Martinvl ( talk) 05:07, 27 June 2012 (UTC)
Section "Terminology", 4th bullet: "In 2006 ... the CIPM cataloged the dalton alongside the unified atomic mass unit as a "Non-SI units whose values in SI units must be obtained experimentally: Units accepted for use with the SI".[2] "
Could one of the main authors straighten this sentence out? Thanks for your efforts, and best regards: Herbmuell ( talk) 00:54, 11 May 2015 (UTC)
The comment(s) below were originally left at Talk:Dalton (unit)/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.
Please explain something to me. If amu "is defined to be one twelfth of the mass of an unbound atom of the carbon-12 nuclide, at rest and in its ground state" and Avagadro's constant is "the number of carbon-12 atoms in 12 grams (0.012 kg) of unbound carbon-12 in its ground state" then why is 1 amu given as:
1 u = 1/NA gram = 1/ NA gram (where NA is Avogadro's number) Shouldn't it be: 1 u = 1/12 (1/NA) 66.245.41.18 18:33, 30 June 2007 (UTC) |
Last edited at 21:47, 4 February 2010 (UTC). Substituted at 08:33, 29 April 2016 (UTC)
I have a couple of questions about this line:
In the first place, it doesn't explain how carbon-12 minimises divergence. My uninformed guess would have been that the value of the unified amu is about halfway between those of the chemistry amu and the physics amu.
In the second place, Holden Chemistry International (Jan–Feb 2004) pages 4–7 says:
(I note that Holden's 275 ppm differs from the 282 ppm used in our article, but there I expect we are more accurate.) jnestorius( talk) 12:21, 30 March 2017 (UTC)
With the official change of the kg, mole and other units in May 2019, the Dalton is being officially redefined as 1 kg/kmol (aka 1 g/mol) and the unified atomic mass unit is also being rendered obsolete. This article needs a rewrite to reflect the change and move the carbon-12 definition into the history section. Also, I think we need to revisit renaming the article to Dalton. Jasoninkid ( talk) 18:57, 26 January 2019 (UTC)
The more I'm reading we need to hold of as it looks like the Dalton/amu may have got stuck in an ill-defined Netherland with the new redefinition. Jasoninkid ( talk) 19:05, 26 January 2019 (UTC)
References
There is a persistent problem with the authoritative and prevailing scientific definition, units, and language being deprecated by editors in favor of vernacular and use in preparatory texts. These less authoratative and professional uses should be accurately reflected but not take primacy over SI, IUPAC, and prevailing science.
a) example: Da being moved to a primary position in front of u, the official SI symbol for this unit. Da is specifically recognized and acceptable for use with the SI unit system as a synonym of u. This relationship is not accurately reflected in the current article, even as a footnote. This is misleading.
b) example: The use of amu as an abbreviation of the unified atomic mass unit is only prevalent in elementary school and some college texts. It is not particularly widely used in the primary scientific literature. The use of 'amu' as unit is even more unacceptable, although it does occur. The current version of the article states simply that this is "common", which is grossly misleading and ignores both the prevailing use in the scientific literature today and authoritative sources (e.g. IUPAC). -- Nick Y. ( talk) 14:53, 17 July 2019 (UTC)
I propose that the name of this page be changed to "dalton". This is consistent with other units, such as joule, meter, etc. The current page would become a redirect, as well as all the other similar variations. An acceptable alternative would be to change the name to "unified atomic mass unit"; however, "unified atomic mass unit" and its symbol "u" are much less commonly used yet similarly accepted by authoritative sources. Recently "dalton" has been preferred in authoritative definitions of units over "unified atomic mass unit". Importantly, the current page name "atomic mass unit" is not the name of any widely used or authoritatively sanctioned modern unit. I understand that "atomic mass unit" can also be interpreted generally as "units of mass used for atomic scale objects"; however, this is like naming the "joule" page as "energy unit". - Nick Y. ( talk) 19:23, 22 October 2019 (UTC)
Note that there is a related conversation above from nearly a decade ago. The crux of the consensus was that as long as the dalton is an "alternative" to the unified atomic mass unit the name should not be changed. Dalton is now the primary unit used by the current SI definitions and the unified atomic mass is a secondary note stating that it is equivalent and another name for the same unit. Bureau International des Poids et Mesures (2019): The International System of Units (SI), 9th edition, English version, page 134. Available at the BIPM website – Nick Y. ( talk) 17:10, 25 October 2019 (UTC)
The result of the move request was: The article is moved per the excellent arguments of the proposer. However there is not consensus at this time to move the dab page. — Martin ( MSGJ · talk) 21:50, 1 November 2019 (UTC) — Martin ( MSGJ · talk) 21:50, 1 November 2019 (UTC)
Atomic mass unit → Dalton (unit) – This is a proposal to make the following page move, redirect, and new page: Atomic mass unit → Dalton (unit) & Redirect dalton → Dalton (unit) & Add Dalton (disambiguation) The reasons are:
– Proposed by Nick Y. ( talk) 20:24, 25 October 2019 (UTC) Please support or oppose below and briefly state reason (add more extensive discussion in the section above):
Some older papers use M(r), I think molar mass, relative. Can this wikipedia main page explain how to convert M(r) to Dalton? Is it 1:1? It's hard to search for this. 2A02:8388:1602:6D80:3AD5:47FF:FE18:CC7F ( talk) 19:32, 13 May 2021 (UTC)
What is the plural of Dalton? Daltons? 5000 Daltons for a protein? Or 5000 Dalton instead? The main article should clarify that IMO. Right now I will stick with the singular but perhaps I am wrong. 2A02:8388:1602:6D80:3AD5:47FF:FE18:CC7F ( talk) 16:45, 15 May 2021 (UTC)
The article begins, "The dalton... is a... unit of mass defined as 1/12 of the mass of a[n]... atom of carbon-12 in its nuclear and electronic ground state and at rest." ("At rest" refers to invariant mass aka rest mass.) I think "at rest" is unnecessary, because " relativistic mass" is a fiction: mass stays the same, it's just that there is the Lorentz factor γ = 1/(1 – v2/c2)1/2, c = speed of light. Solomonfromfinland ( talk) 13:15, 17 July 2023 (UTC)
I edited this article for concision. One thing i did, was, for superscript, replacing the wikicode "<sup></sup>" with the more concise "{{sup|}}". Likewise for subscript. Okay? Solomonfromfinland ( talk) 13:32, 17 July 2023 (UTC)
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Can someone please explain the units and use of parentheses used in this equation from the article: 1 u = 1.660538782(83)×10−27 kg = 931.494027(23) MeV/c² The article is supposed to be accessible and I don't think this is. 139.133.7.37 ( talk) 12:25, 8 November 2008 (UTC)
In biology, the Dalton is often used in this way: "Only proteins smaller than [...]KDa can pass through this channel/pore." Since it is a unit of mass, isn't this strange? Are mass and size correlated in proteins? Since proteins can fold in many different ways, I would think that some proteins of a certain mass would and others would not fit through a channel/pore. Anyone?
Also the mass of any molecule can be converted in its number of protons + electrons, eg 1kDa is roughly 1000 protons and neutrons, and that is probably a good proxy for how large the protein will look like. I have read somewhere that after a 1MDa proteins don't even diffuse any more. — Preceding unsigned comment added by 188.223.9.243 ( talk) 23:43, 30 June 2011 (UTC)
Why did they choose the AMU convention of 1/12 of C12 rather than the original standard with 1/16 016?
How come only biological sciences use the Dalton unit? In chemistry there is rarely a unit. The header in a table of molecular weights would be labelled 'mw' or 'molecular weight' with no unit. Just a guess, but it may be because, when talking about large molecular weights, 'kilo (no unit)' sounds kind of stupid.
Physicists have the opposite problem - small values rather than large values. When they talk about mass deficiency rather than binding energy, it might well be appropriate to use mDa or μDa rather than milli or micro atomic mass units. Martinvl ( talk) 18:56, 24 April 2012 (UTC)
How do you change Atonic mass into pounds?
I removed the following paragraph; I think it's overly simplistic and illustrates a principle of college algebra rather than of atomic masses. It is certainly not relevant to the amu unit. It also uses the term "relative atomic mass" in a strange way and. AxelBoldt 16:44, 9 Oct 2004 (UTC)
A simple calculation may be used to calculate the relative atomic mass of the sample. This is demonstrated in the following example.
Ion | Relative Mass | Percentage Abundance |
11C+ | 11 | 70% |
13C+ | 13 | 30% |
Therefore, the relative atomic mass of the Carbon sample is:
[this is not the true atomic mass of carbon, it is merely illustrative]
The number on the page for u didn't agree exactly with the CODATA value referenced at the bottom. CODATA is state of the art, I have changed it to the CODATA value.
Is it 1/12 of a C12 nucleus or atom? I can't remember my high school physics, and some sites say it's "nucleus" and a few say it's "atom".
It's both, the mass of the atom is the mass of the nucleus, since the mass of the electron is negligible. Mchmike 03:19, 19 October 2006 (UTC)
No, it's not negligible. The electrons weigh something. In order to be accurate, the 1/12 must be defined as something, and the pure number 1/12 is infinitely percise, hence it must be 1/12 of either the nucleus or atom. 65.185.93.86 ( talk) 21:31, 22 May 2008 (UTC)
No. It is definitely the atom. The mass of the electron is about 1/2000 of the mass of a nucleon, much larger than the accuracy to which nuclear masses can be determined. It is negligible for some purposes, but not for all.
I read in two college texts that the absolute mass of the atomic mass unit is 1.66054E-24 grams. Wouldn't that make kilograms .00166054E-27? RAW 18:54, 24 April 2007 (UTC)
Perhaps this article could be edited to more obviously show the relation between Daltons and the molecular mass in g/mol? Roddyboy 03:28, 15 May 2007 (UTC)
The most common use of 'Daltons' is as a synonym for g/mol. When someone talks about a 254 kDa protein, they mean it has a molecular mass of 254,000 g/mol. I think this article needs to make this clear. 27.54.43.66 ( talk) 03:46, 28 May 2011 (UTC)
The author is correct when writing that the molecular mass of water is 18.0106 g/g-mol. However, in some industries (especially petroleum refining) in the United States (perhaps elsewhere), lb/lb-mol is the preferred term. Furthermore, there it is called molecular weight. As one could see by inspection, 1 g/g-mol = 1 lb/lb-mol. —Preceding unsigned comment added by 69.42.7.158 ( talk) 02:09, 11 August 2008 (UTC)
Why is only 1/12th of the carbon atom taken for amu? Why not of any other element? —Preceding unsigned comment added by 202.125.143.73 ( talk) 16:48, 21 August 2008 (UTC)
This is because Ar(H) = 1/12 of Ar( carbon-12) = 1. Remember that atomic weight (Ar) is a ratio. It is the molar mass (M) = Ar * Mu, where Mu is the molar mass constant, 1 gram/mole. Thus, M(H) = 1 g/mole = 1 amu. -- Bsodmike ( talk) 20:36, 18 July 2009 (UTC)
Sorry, referring maybe I am being a bit tired/dense, where does it say that the preferred usage for large or small values is Dalton? It says it is "often used" sure, but the text is suggesting it is somehow preferred? ( diff in question) User A1 ( talk) 21:54, 11 August 2010 (UTC)
My understanding is that both usages are equally acceptable. There is a definite preference among biochemists, molecular biologists and polymer scientists for the name "dalton", simply because they work in kilodaltons. Chemists, who tend to work in the range 1–1000 Da, usually ignore the unit or use g/mol (which is numerically equivalent). I've never seen "millidalton" used in practice, but it's not incorrect and it might catch on in the future. It's not a big practical issue, and so we shouldn't give it WP:UNDUE attention. Physchim62 (talk) 18:13, 12 August 2010 (UTC)
You guys may be interested in the following:
"A suggestion has been made in the CCU (communicated to C2 through Brian Petley), that the time has come to replace the name and symbol of the unified atomic mass unit, u, with dalton, Da. The grounds are that the current name is a mouthful and the need to emphasize the concept of "unified" is long gone. The dalton is widely used in chemical mass spectrometry community (e.g. bio-chemistry). Its use will also bring the polymer chemists into the SI community. There is possible confusion with the astronomical unit ua, and people want to use u or U to denote the unit one. There was considerable comment on this matter from many of the SUNAMCO members. In the short term the proposed change simply endorses the present reality that both the atomic mass unit and Dalton are in use."
It does seem to me that the powers that be (BIPM, IUPAC, IUPAP) are moving towards adopting Dalton more widely, but not doing anything to deprecate the AMU (they rarely deprecate any unit). I hope that helps. Lightmouse ( talk) 20:44, 13 August 2010 (UTC)
Be careful here. The "amu" is clearly deprecated (in 1961). The "u": maybe, maybe not. Small note: MilliDalton is in fact in common usage as some googling has shown. It's use arises from differences between masses with modern, highly accurate measurements.-- Nick Y. ( talk) 07:21, 17 August 2010 (UTC)
No consensus to move. Vegaswikian ( talk) 18:19, 30 August 2010 (UTC)
Atomic mass unit → Dalton (unit) — This is one of the earliest articles in Wikipedia (2002). The article "Dalton (unit)" had a short life in 2005 before being merged with this article on grounds that "It is often used in biochemistry and molecular biology although it was never approved by the Conférence Général des Poids et Mesures CGPM". Since then a number of things have happened (referenced in article):
In addition, the University of Oxford Style Guide for Life Sciences listed the dalton as an allowable unit (along with SI), but did not mention the unified atomic mass unit. This suggests to me that that we should at least be considering moving the text of this article to the article "Dalton (unit)". My assessment is that since the two articles have been merged, there has been a drift towards using the dalton in preference to the unified atomic mass unit and that the split in the literature is now 51% to 49%. (I am not going to justify these figures). Martinvl ( talk) 19:42, 23 August 2010 (UTC)
I have made a number of changes to the initial rewrite. Firstly I have rewritten the lede so that it only discusses the atomic mass unit without mentioning its relationship to the mole. The section, formerly called "Definition and Measurement" needs considerable rework. I have renamed it "Relationship to the mole" as that is what the content appears to be. Thuis section could well be expanded to show how it is used in the world of chemistry. The content certainly has nothing to do with measurement as it can be measured by any number of different methods. A similar section could be used to show how it is used in the world of physics, looking at Mass deficiency and the like.
I also think that the History section needs considerable expansion, showing how the difference definitions were brought together and why it is called the unified atomic mass number. Martinvl ( talk) 19:56, 25 August 2010 (UTC)
We should be aware that a wiki article's inertia is a lot less than that of a standards body. Also, we should not try to pre-emptively supply information. Let us worry about future hurdles in the future. We all seem to be better at writing talk pages than articles, myself included. User A1 ( talk) 15:13, 26 August 2010 (UTC)
The conversion factor between daltons and kilograms has a name, it's called the atomic mass constant: I find it remarkable that the article doesn't mention this (because it's been removed). Nor does the article give any information about how the value of this conversion factor is calculated: the equation mu = Mu/NA (referenced to the CODATA paper) needs to be reinstated, or readers are left with the impression that you can weigh a carbon atom. Physchim62 (talk) 13:32, 27 August 2010 (UTC)
I flagged this edit [4] as improper synthesis for the reasons outlined in this RfC: RfC:_Is_Kendrick_unit_original_research. -- Kkmurray ( talk) 17:26, 28 October 2010 (UTC)
I have modified the unfobox to show the dalton as an alternative to the amu, because firstly, it is just that and secondly, the article "Dalton (unit)" redirects to this artcile. Martinvl ( talk) 05:07, 27 June 2012 (UTC)
Section "Terminology", 4th bullet: "In 2006 ... the CIPM cataloged the dalton alongside the unified atomic mass unit as a "Non-SI units whose values in SI units must be obtained experimentally: Units accepted for use with the SI".[2] "
Could one of the main authors straighten this sentence out? Thanks for your efforts, and best regards: Herbmuell ( talk) 00:54, 11 May 2015 (UTC)
The comment(s) below were originally left at Talk:Dalton (unit)/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.
Please explain something to me. If amu "is defined to be one twelfth of the mass of an unbound atom of the carbon-12 nuclide, at rest and in its ground state" and Avagadro's constant is "the number of carbon-12 atoms in 12 grams (0.012 kg) of unbound carbon-12 in its ground state" then why is 1 amu given as:
1 u = 1/NA gram = 1/ NA gram (where NA is Avogadro's number) Shouldn't it be: 1 u = 1/12 (1/NA) 66.245.41.18 18:33, 30 June 2007 (UTC) |
Last edited at 21:47, 4 February 2010 (UTC). Substituted at 08:33, 29 April 2016 (UTC)
I have a couple of questions about this line:
In the first place, it doesn't explain how carbon-12 minimises divergence. My uninformed guess would have been that the value of the unified amu is about halfway between those of the chemistry amu and the physics amu.
In the second place, Holden Chemistry International (Jan–Feb 2004) pages 4–7 says:
(I note that Holden's 275 ppm differs from the 282 ppm used in our article, but there I expect we are more accurate.) jnestorius( talk) 12:21, 30 March 2017 (UTC)
With the official change of the kg, mole and other units in May 2019, the Dalton is being officially redefined as 1 kg/kmol (aka 1 g/mol) and the unified atomic mass unit is also being rendered obsolete. This article needs a rewrite to reflect the change and move the carbon-12 definition into the history section. Also, I think we need to revisit renaming the article to Dalton. Jasoninkid ( talk) 18:57, 26 January 2019 (UTC)
The more I'm reading we need to hold of as it looks like the Dalton/amu may have got stuck in an ill-defined Netherland with the new redefinition. Jasoninkid ( talk) 19:05, 26 January 2019 (UTC)
References
There is a persistent problem with the authoritative and prevailing scientific definition, units, and language being deprecated by editors in favor of vernacular and use in preparatory texts. These less authoratative and professional uses should be accurately reflected but not take primacy over SI, IUPAC, and prevailing science.
a) example: Da being moved to a primary position in front of u, the official SI symbol for this unit. Da is specifically recognized and acceptable for use with the SI unit system as a synonym of u. This relationship is not accurately reflected in the current article, even as a footnote. This is misleading.
b) example: The use of amu as an abbreviation of the unified atomic mass unit is only prevalent in elementary school and some college texts. It is not particularly widely used in the primary scientific literature. The use of 'amu' as unit is even more unacceptable, although it does occur. The current version of the article states simply that this is "common", which is grossly misleading and ignores both the prevailing use in the scientific literature today and authoritative sources (e.g. IUPAC). -- Nick Y. ( talk) 14:53, 17 July 2019 (UTC)
I propose that the name of this page be changed to "dalton". This is consistent with other units, such as joule, meter, etc. The current page would become a redirect, as well as all the other similar variations. An acceptable alternative would be to change the name to "unified atomic mass unit"; however, "unified atomic mass unit" and its symbol "u" are much less commonly used yet similarly accepted by authoritative sources. Recently "dalton" has been preferred in authoritative definitions of units over "unified atomic mass unit". Importantly, the current page name "atomic mass unit" is not the name of any widely used or authoritatively sanctioned modern unit. I understand that "atomic mass unit" can also be interpreted generally as "units of mass used for atomic scale objects"; however, this is like naming the "joule" page as "energy unit". - Nick Y. ( talk) 19:23, 22 October 2019 (UTC)
Note that there is a related conversation above from nearly a decade ago. The crux of the consensus was that as long as the dalton is an "alternative" to the unified atomic mass unit the name should not be changed. Dalton is now the primary unit used by the current SI definitions and the unified atomic mass is a secondary note stating that it is equivalent and another name for the same unit. Bureau International des Poids et Mesures (2019): The International System of Units (SI), 9th edition, English version, page 134. Available at the BIPM website – Nick Y. ( talk) 17:10, 25 October 2019 (UTC)
The result of the move request was: The article is moved per the excellent arguments of the proposer. However there is not consensus at this time to move the dab page. — Martin ( MSGJ · talk) 21:50, 1 November 2019 (UTC) — Martin ( MSGJ · talk) 21:50, 1 November 2019 (UTC)
Atomic mass unit → Dalton (unit) – This is a proposal to make the following page move, redirect, and new page: Atomic mass unit → Dalton (unit) & Redirect dalton → Dalton (unit) & Add Dalton (disambiguation) The reasons are:
– Proposed by Nick Y. ( talk) 20:24, 25 October 2019 (UTC) Please support or oppose below and briefly state reason (add more extensive discussion in the section above):
Some older papers use M(r), I think molar mass, relative. Can this wikipedia main page explain how to convert M(r) to Dalton? Is it 1:1? It's hard to search for this. 2A02:8388:1602:6D80:3AD5:47FF:FE18:CC7F ( talk) 19:32, 13 May 2021 (UTC)
What is the plural of Dalton? Daltons? 5000 Daltons for a protein? Or 5000 Dalton instead? The main article should clarify that IMO. Right now I will stick with the singular but perhaps I am wrong. 2A02:8388:1602:6D80:3AD5:47FF:FE18:CC7F ( talk) 16:45, 15 May 2021 (UTC)
The article begins, "The dalton... is a... unit of mass defined as 1/12 of the mass of a[n]... atom of carbon-12 in its nuclear and electronic ground state and at rest." ("At rest" refers to invariant mass aka rest mass.) I think "at rest" is unnecessary, because " relativistic mass" is a fiction: mass stays the same, it's just that there is the Lorentz factor γ = 1/(1 – v2/c2)1/2, c = speed of light. Solomonfromfinland ( talk) 13:15, 17 July 2023 (UTC)
I edited this article for concision. One thing i did, was, for superscript, replacing the wikicode "<sup></sup>" with the more concise "{{sup|}}". Likewise for subscript. Okay? Solomonfromfinland ( talk) 13:32, 17 July 2023 (UTC)