Talk:Dalton (unit)

message: 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)
replies: text: C12 has 6 electrons, I guess they are accounted for in the 12 daltons that a C12 weights, since the definition mentions the electronic ground state. 80.215.74.36 (talk) 12:15, 22 October 2022 (UTC)
thread_title:  Nucleus or Atom? 

message: 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)
replies: text: 0.00166054E-27=1.66054E-30. You are shifting by 6 decimal places instead of three. The article is correct 1.66054E-27kg==1.66054E-24g--Nick Y. 20:06, 24 April 2007 (UTC)
thread_title:  Atomic mass unit or Dalton' mass? 

message: 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)
replies: text: The relation which you are addressing is a very impractical but very simple relation that I would advise you to be uninterested in. It is somewhat addressed in the example just to demonstrate the definition. Perhaps you mean the relationship between the molecular mass in daltons and the molar mass in g/mol? I have added language to make this more clear without going into detail since it is really should not be a part of this article. This relationship is really very, very complicated and depends on multiple molecular masses and statistical distributions of isotopes and averaging across different locations around the globe etc.--Nick Y. 18:57, 15 May 2007 (UTC)
replies: text: Cool thanks for that. Yeah I meant the molar mass in g.mol-1 vs. the molecular mass in Daltons. It's a very clear explanation now :-) Roddyboy 03:18, 16 May 2007 (UTC)
thread_title:  Dalton vs g/mol 

message: 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)
thread_title:  Other units 

message: 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)
replies: text: If you do a regression analysis of the reported mass values of the incremental 4 nucleon (alpha particle?) increases of the A = 2Z elements you get a least squares curve of expected mass values over this limited range of atomic mass values. It should be noted that this curve gives values for C12 and O16 which is slightly greater than their reported values, and that the reported O16 value is closer to the least value curve than the C12 curve. This might indicate a tendency for the reported AMU values of atomic masses to be biased towards underestimating the true values in both cases, but that the estimating values for the O16 values would be more correct.WFPM (talk) 14:29, 31 July 2009 (UTC)
replies: text: I believe that originally the physicists used hydrogen, but the chemists used oxygen, so as a compromise both disciples agreed to use carbon. Martinvl (talk) 10:51, 22 January 2010 (UTC)
replies: text: The physicists used 16O = 16, while the chemists used O = 16 (at natural, and hence variable, isotopic composition). 12C = 12 was indeed a compromise solution: the full story can be found in this free-access article. Physchim62 (talk) 17:57, 12 August 2010 (UTC)
thread_title:  Atomic mass unit 

message: I flagged this edit  as improper synthesis for the reasons outlined in this RfC: RfC:_Is_Kendrick_unit_original_research. --Kkmurray (talk) 17:26, 28 October 2010 (UTC)
replies: text:  As explained in RfC:_Is_Kendrick_unit_original_research, the Kendrick mass unit is sourced from a single source . It therefore per definition cannot be a synthesis. Therefore I removed the flag. Kehrli (talk) 21:43, 28 October 2010 (UTC)
replies: text: I removed Kendrick unit from the infobox. --Kkmurray (talk) 18:44, 16 March 2011 (UTC)
thread_title: Kendrick mass and improper synthesis

message: 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)
thread_title:  Infobox 

message: 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] "
*In the linked pdf, table 7 on p. 126 of the book (p. 34 of the pdf) is headed  "Non-SI units whose values in SI units must be obtained experimentally". The additional sentence "...: Units accepted for use with the SI" is not in the table header (it appears earlier) and seems to make things unnecessarily complicated. 
*Also, there is a clash between singular ("the dalton alongside the unified atomic mass") and plural ("Non-SI-units"). 
*The word "alongside" seems badly chosen to me, since dalton and u are the same. 
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)
thread_title:  This sentence could be improved 

message: Substituted at 08:33, 29 April 2016 (UTC)
thread_title: Assessment comment

message: I have a couple of questions about this line:
:The choice of carbon-12 was made to minimise further divergence with prior literature.
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:
:Nier suggested to Mattauch that the 12C = 12 mass scale be adopted because of carbon's use as a secondary standard in mass spectrometry. Also, 12C = 12 implied acceptable relative changes in the atomic weight scale, i.e., 42 parts-per-million (ppm) compared to 275 ppm for the 16O = 16 scale (which would not [be] acceptable to chemists).
(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)
replies: text: I have actually seen an oxygen 16 periodic table.   It was not new :-)     People come up will all sorts of justifications, but the reality is that 1H, 12C, and 16O all work just fine.  Standardization on something was and is more important than which one you choose in this case.   Don't try to read to much into these decisions as if they were made by the scientific Justice League of Nations.  AManWithNoPlan (talk) 13:12, 30 March 2017 (UTC)
replies: text: I don't think your comment is of any help in explaining the sentence "The choice of carbon-12 was made to minimise further divergence with prior literature". jnestorius(talk) 12:27, 31 March 2017 (UTC)
replies: text: Your Holden quote suggests that the C12 scale is not "halfway between natural-O and O16, but rather very very close to natural O. So that's my guess. "Prior literature" really means "prior chemistry literature", i.e. "prior literature using the natural-O scale". And it minimizes divergence because natural-O happens to be 15.999/12 the mass of C12. Whereas O16 is significantly different, 15.995/12 the mass of C12. (See Oxygen-16.) Do you agree? I'm not an expert on this. --Steve (talk) 13:57, 31 March 2017 (UTC)
thread_title:  Why carbon-12? 

message: 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)
replies: text: Did you see the section Atomic mass unit#Relationship to SI? It says that carbon-12 will continue to be the definition. There's a reference for that pointing to a quote from BIPM. Do you agree, or what do you think? I didn't write that section, and don't know what's correct. --Steve (talk) 22:57, 26 January 2019 (UTC)
replies: text: No, carbon-12 is no longer a part of the definition. The SI-unit mol is defined https://www.bipm.org/en/measurement-units/ through having a prescribed value of the Avogadro constant NA as exactly 6.022 140 76 × 1023 mol–1 User:Saittam  — Preceding undated comment added 13:24, 7 April 2021 (UTC)
thread_title:  2018/2019 redefinition of the Dalton 

message: 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)
replies: text: I'm not convinced that your point (a) is correct in modern terms.  The ninth SI brochure (and you do seem to prefer it, amongst others as an authoritative guide), for example, uses the dalton and its symbol Da exclusively in the main text and lists it (without the unified atomic mass unit) in Table 8: Non-SI units accepted for use with the SI Units.  The unified atomic mass unit and is symbol u are listed only once, and then only in a footnote to this table.  The inference is that the dalton is the primary unit accepted for use with the SI, and that the unified atomic mass unit is potentially no longer so, albeit being recognised as being the same unit (the SI would have erred if it had failed to mention it even if it is not considered "accepted for use with the SI", since that would have left its definition in an ambiguous state).  My perception is that to call this "creeping vernacular" is inappropriate. Wikipedia should reflect current usage and science, not usage that predominated ten years ago.  Even standards that have not been updated for several years reflect dated usage.  Can you give recent authoritative examples that suggest the Da has not become the preferred term and symbol?  —Quondum 22:07, 17 July 2019 (UTC)
replies: text: Agreed. You have provided an authoritative source for the reversal of primacy of the Da over u. My point on creeping vernacular of 'amu' stands. the amu abbreviation is neither widely used nor is it authoritatively sanctioned. When it is used as an abbreviation it is also often used by the same source as a unit, which is particularly contrary to authoritative source recommendation and counter to prevailing scientific usage. --Nick Y. (talk) 21:15, 19 July 2019 (UTC)
replies: text:  Thanks for the response (and the edit).  I strongly agree with your general point: that editors have a tendency edit in the "common view", which is all too often biased to what they have picked up at school or are familiar with as laymen, and that an encyclopaedia should reflect authoritative use within the discipline.  The mention of the "amu" probably does not even belong in the lead, but I guess this will need someone who is prepared to research the history a bit to decide on its notability.  This is also complicated by the semi-automatic abbreviation of "unified atom mass unit" to "atom mass unit".  —Quondum 22:18, 19 July 2019 (UTC)
thread_title:  Authoratative vs. Vernacular 

message: 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)
thread_title:  M(r) to Dalton 

message: 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)
replies: text: Daltons (in lowercase when it doesn't start a sentence), much like newtons, pascals, etc... This is covered by the basic rules of grammar and doesn't need to be featured in an article about the topic.  Headbomb {t · c · p · b} 18:03, 15 May 2021 (UTC)
thread_title:  Plural 

message: 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 – v/c), c = speed of light. Solomonfromfinland (talk) 13:15, 17 July 2023 (UTC)
thread_title:  At rest 

message: I edited this article for concision. One thing i did, was, for superscript, replacing the wikicode "" with the more concise "". Likewise for subscript. Okay? Solomonfromfinland (talk) 13:32, 17 July 2023 (UTC)
thread_title:  Wikicode