Talk:Kendrick mass

Merge Kendrick unit to Kendrick mass

Per original (de)PROD[1] and move.[2]: there is a Kendrick mass but not a Kendrick unit. Remove the redundant content fork. --Kkmurray (talk) 03:06, 18 August 2010 (UTC)

Better idea: merge Kendrick mass into Kendrick unit or even Kendrick mass unit. Of course there is a Kendrick mass unit. "Kendrick mass" is not specific enough. What exactly is the meaning of "Kendrick mass"? Every mass unit is a mass, but not every mass is a mass unit. Kendrick mass unit corresponds to "atomic mass unit" (which is not called "atomic mass"), to Newton (unit), Dalton_(unit), and so on.

Kehrli (talk) 12:20, 18 August 2010 (UTC)

Kendrick called it a "mass scale" not a "mass unit" as do all others subsequently in the peer reviewed literature. Kendrick advocated "adoption of a mass scale in which the mass of the CH₂ radical is taken as 14.0000 mass units.^{doi:10.1021/ac60206a048} No mention of unit. A search of Google Scholar for "Kendrick Mass Unit" yields no publications whereas "Kendrick Mass Scale", "Kendrick Mass Defect", and "Kendrick Mass" net 255, 186 and 90, respectively. Nothing whatsoever in the literature about a unit with the symbol Ke. This appears to be original research. In response to "what is Kendrick mass", Marshall says that "conversion from IUPAC mass to “Kendrick” mass [involves] ... multiplying each mass by 14.00000/14.01565".^{doi:10.1021/ac010560w} There are many ways to talk about mass in mass spectrometry, but not all of them have associated units. --Kkmurray (talk) 13:48, 18 August 2010 (UTC)

1) I get many Google results when I search for "Kendrick Mass units".

2) The terminology "scale" may have been common when Kendrick wrote his paper back in 1964 or so. Today "scale" is outdated. It is very seldom that one hears today of the "Dalton scale", the "meter scale", the "newton scale" and so on. Also in the IUPAC green book the term "scale" is used rather seldom. I am not saying it is wrong, but I think in Wikipedia we should use current terminology.

3) Where there is a scale, there is a unit. The two terms are not equivalent but they always go together. It is the equivalent of a "stair" and a "step" relation.

4) Marshall also used the term "Kendrick mass units". Look it up. The paper is referenced in the Wikipedia article.

5) It used to be the case that scientists used "scales" without naming the units. This is no longer good practice. It should definitely not be promoted in Wikipedia. Please read the IUPAC green book for current use and terminology of quantities and units in chemistry.

6) There are many ways to talk about the earth. During 99% of human life the earth was considered to be flat. Does that mean we should write in Wikipedia the earth is flat? I don't think so. This is why mass units should have proper names in Wikipedia.

7) The "Kendrick mass unit" or "Kendrick" complies with modern terminology, it is used in the (modern) literature, we should use it.

8) Wikipedia is not museum

9) You asked for references. They already are in the article.

10) Kendrick may have been a modest person and therefore did not use the term "Kendrick mass unit". It would be somewhat strange to name a unit after oneself. This is why only his fellow scientists started using "Kendrick mass units".

Kehrli (talk) 16:21, 18 August 2010 (UTC)

If one makes a plot of relative abundance as a function of Kendrick mass, the axis is units (plural) of Kendrick mass. That does not imply that there is a unit (singular) of Kendrick mass with a symbol Ke. That is why you get multiple hits for "Kendrick mass units" (plural) and none for ""Kendrick mass unit" (singular). People are making plots with Kendrick mass as the x-axis, but they are not defining or using a unit of Kendrick mass or a symbol for that unit. I can make a plot of foxes caught as a function of hounds run and the x axis is in units of hounds. That does not imply that there is such a thing as a "hound unit" with symbol Ho. This does not mean that there cannot ever be a defined Kendrick unit with symbol Ke, it's just that Wikipedia is not the place to make a proposal for adopting this new unit. --Kkmurray (talk) 13:46, 19 August 2010 (UTC)

1) Mass is a physical quantity that is regulated by ISO, IUPAP and IUPAC. Foxes and hounds are not. If they were, all three organizations would actually create a unit for foxes and hounds, because that is how quantities are handled in the field of science. Mass quantities do have a unit. Period.

2) A mass is a mass is a mass. Strictly speaking there is no such thing as a Kendrick mass. There is no kg mass, there is no Dalton mass, there is no pound mass. "Kendrick mass" is a sloppy term for "a mass measured in Kendrick units". Kendrick mass indicates the same mass as the mass measured in any other units. In other words: the mass of a molecule is always the same, independent whether it is measured in Da, kg, lb, Kendrick or any other mass units. It is just the numerical value in front of the unit that changes: m = x kg = y Da = z Ke are all the same. The molecule does not change its mass depending on the unit it is measured. In this sense, the Kendrick mass unit is superfluous. Kendrick could just have used the modulo function. But he did not. He introduced a new mass scale, and with it comes a new mass unit.

3) Every mass scale implies units which implies a single unit. Same as every stair implies steps which implies a single step.

4) I did not "propose" the name "Kendrick mass unit", nor its name Kendrick, nor the symbol Ke. It is all in the literature and it is referenced in the article. Please read the article thoroughly before you make false accusations.

Kehrli (talk) 14:28, 21 August 2010 (UTC)

Could you provide a citation (DOI + page number) for the work that defines the kendrick unit and symbol Ke? Thanks. --Kkmurray (talk) 22:03, 22 August 2010 (UTC)

You find the article referenced in the external link section in the article Kendrick unit. --80.219.224.184 (talk) 11:06, 28 August 2010 (UTC)

I found "Kendrick units" (plural) but no definition of a "Kendric unit" (singular) or Ke symbol. Nothing that would suggest that this in not original research. --Kkmurray (talk) 15:28, 29 August 2010 (UTC)

Well, what should I say. I do find "... It simplifies the interpretation of a complex organic mass spectrum by expressing the mass of hydrocarbon molecules in Kendrick units (where m(12CH2)=14 Ke) instead of Dalton (where m(12C)=12 Da) (Kendrick, 1963)." Dalton mass units and Kendrick mass units have to be treated the same way. It is that simple. These are both units, period. IUPAC explains exactly how to treat units. Could you please read the green book? It is all in there. Alternatively you can look it up on wikipedia. Please show me a metrology textbook that proves that there is a "mass scale" without a unit. That would be the same as a stair without steps. It does not exist. It is OR. --Kehrli (talk) 00:52, 2 September 2010 (UTC)

Your quote seems to come from this work: [3], coincidentally published the day you recreated the Kendrick unit article. My suggestion is to merge per the above and note that the unit/symbol has appeared recently in a single article but has otherwise not been used. --Kkmurray (talk) 13:52, 2 September 2010 (UTC)

Based on my (admittedly cursory) read of the provided literature, I would say the best place for the information right now is Kendrick Mass. At this point, it seems more like a defined quantity to make data analysis convenient, rather than a true unit of measure. This can change in the future, and the article might have to change with it. But as of right now, a paper outlining the concept from 1963 and a single reference using the same concept in 2010 isn't really enough to call it a "unit". Canada Hky (talk) 14:20, 24 September 2010 (UTC)

Here is a crash course in metrology: measuring a quantity means comparing it with a reference quantity. These reference quantities are called Units of measurement. This is all defined this way by IUPAP, ISO 31, and IUPAC. The term "defined quantity" from Canada Hky however is nowhere defined in these documents. What does it mean? A constant quantity? A quantity that is defined? The mass of Canada Hky is a defined quantity, but it is not constant. It changes when he is eating, for example. Therefore it is not suitable as a "reference quantity" or a "unit" and should not be used here. Also, as already mentioned above: the term "Kendrick mass units" is widely used, since many years. Google it. It is old. Then google for ""units of Kendrick mass". There is not a single hit. We need to keep wikipedia consistent. Since we have a dalton mass unit (not a dalton mass), a atomic mass unit (not atomic mass), a kg mass unit (not a kg mass) we need a Kendrick mass unit. This is modern terminology in metrology. When Kendrick introduced his scale in 1963 these rules were not yet established. Units were less common, especially in chemistry. (Side note: Some chemists still think that atomic mass units are dimensionless, e.g. do not have a unit. They do not realize that has changed a long time ago.) Today, masses should be measured in quantites of dimension mass and therefore automatically need a mass unit. These are the modern rules (even if 50 year old literature seems to suggest otherwise). By creating a Kendrick mass scale one automatically creates a mass unit in the same way as when you make a stair you automatically create steps. Please read the IUPAP red book, ISO 31, and IUPAC green book. Google does not free you from reading these international conventions. This article is a matter of metrology, not of chemistry. Please ask a metrologist. If you think chemist are too good to "surrender" to modern rules of metrology then please create your own article (as you have already done), but leave my article alone. Kehrli (talk) 16:57, 25 September 2010 (UTC)

(outdent) I'm not sure we are having the same discussion here. Wikipedia doesn't currently have a Dalton mass unit page, they have a page for Dalton (unit). That is simply a disambiguator. Note that kilogram doesn't have this same disambiguator, because it doesn't need one. What you are discussing isn't an issue of "metrology", its Wikipedia convention. To keep things consistent with Wikipedia, neither of the proposed options are correct. The page should be at Kendrick (unit). I didn't realize that you were comparing to Daltons, etc in terms of what was used on Wikipedia. Canada Hky (talk) 18:29, 25 September 2010 (UTC)

First: I would agree with Kendrick (unit). Second: my discussion is not about Wikipedia convention. It is about metrology. You claim that "Kendrick mass units" are not a unit, but "more like a defined quantity to make data analysis convenient, rather than a true unit of measure". I claim that in metrology there is nothing like "defined quantity to make data analysis convenient" and that according to the rules of metrology it is a unit. It looks like a unit, it is used like a unit, it is refered to as a unit, so it is a unit. The kg unit is something different than the kg mass, which is the realization of the kg unit and stored in Paris. Kehrli (talk) 21:36, 26 September 2010 (UTC)

You were discussing Wikipedia convention "we need to keep Wikipedia consistent" - that has nothing to do with metrology. I'm not particularly interested in the finer points of metrology, I would just like the page to be in the correct place according to Wikipedia convention. I think that is Kendrick (unit). Canada Hky (talk) 23:50, 26 September 2010 (UTC)

Having looked at Units of mass I completely agree that Kendrick (unit) is the best address. Kehrli (talk) 07:41, 29 September 2010 (UTC)

On the other hand, there are Planck mass, solar mass, earth mass, etc., but no corresponding Planck (unit), solar (unit), earth (unit), etc. There is an article on Planck units, but this is the set of fundamental constants normalized to one. Again, there are many ways to express mass without defining a corresponding unit. --Kkmurray (talk) 18:10, 29 September 2010 (UTC)

"Again, there are many ways to express mass without defining a corresponding unit." This statement is completely wrong. In your examples above, Planck mass, solar mass, earth mass are all used as units. It even says so in the corresponding articles. Also, the article Planck units explains that the Planck mass is the unit of mass in the Plank system of units. But I see your question: why are Planck mass, solar mass, earth mass all labeled as mass and not as units? The answer is simple but long: every mass can potentially be used as a unit. Some masses are uniquely defined to be used as a unit. Example: the kilogram mass is stored in Paris and it has no other purpose than being the incarnation of the kg unit. The other approach is to take a famous mass and use it as a unit. Planck mass, solar mass, earth mass are all examples of this second approach. The solar mass is a unit, but its main relevance is not as a unit but as the mass of the sun. If the solar mass would change for some reason and, say, become 10% smaller, the earth would reach a higher orbit and all water would freeze within days. The Planck mass and many other fundamental constants are often used as units. The main relevance of those fundamental constants is not their being a unit, however. It is quite the opposite. Speed of light, elementary charge are good examples that are used as units, but their function as fundamental quantities is much more important. What you call the "Kendrick mass" has its main relevance as a unit. It is probably fair to say that not a single object in the whole universe has the same mass as the Kendrick mass. Neither is it a fundamental constant. It is a unit that has been defined because in its scale of measure the homologous hydrocarbons have the same mass defect. If the Kendrick would have been defined as m(12CH2) then we could argue. But since it is defined as 1/14 * m(12CH2) it is definitely a mass that has no other relevance than being a unit. Kehrli (talk) 09:09, 1 October 2010 (UTC)

RfC: Is Kendrick unit original research?

Does the definition of a unit of mass called Kendrick with symbol Ke constitute original research/synthesis and should Kendrick (unit) be merged with Kendrick mass? Kkmurray (talk) 18:25, 17 October 2010 (UTC)

See also comments above. My position is that there has been no attempt to define a Kendrick unit in the scientific literature, although the concepts of Kendrick mass, the Kendrick mass scale and Kendrick mass defect are widely used. The unit of mass kendrick that is defined in Kendrick (unit) goes beyond the scientific literature and is therefore original research. For background, this article doesn't require a subscription and gives a good overview of Kendrick mass: doi:10.1073/pnas.0805069105 --Kkmurray (talk) 18:41, 17 October 2010 (UTC)

• Kendrick (unit) should be merged with Kendrick mass, or otherwise removed from wikipedia namespace. The Kendrick mass scale is a simple renormalization for the sake of convenience for certain types of molecules and has never been referred to as a unit in and of itself, nor is there any standard abbreviation. These creations are novel to wikipedia and original research. --Nick Y. (talk) 16:03, 20 October 2010 (UTC)

I have added a direct citation into the article Kendrick mass that shows that your claims are not true at all. The Kendrick mass units as well as the symbol Ke is referred in the latest literature. Kehrli (talk) 14:06, 25 October 2010 (UTC)

I did work on the Article to make it less biased and give a more Wikipedia:OR#Neutral_point_of_view. This will help to decide which article has to be merged into which address. Kehrli (talk) 07:25, 25 October 2010 (UTC)

Encyclopedias are for established knowledge and conventions, not a place for trying to grapple with how best to do things. That is for the scientific literature. The *one* paper that you cite is doing an appropriate job of making an argument in the appropriate context, the primary literature. This is not the place for that same argument. --Nick Y. (talk) 14:46, 25 October 2010 (UTC)

I agree that Encyclopedias are for established knowledge and conventions. This is why I am pushing for the conventions established by the IUPAP red book, the IUPAC green book, the ISO 31, and the International vocabulary of metrology instead of some ad-hoc terminology created by non-metrologists 50 years ago. The one paper that I cite keeps much better to the established conventions than anything that was written before. Maybe you should read the conventions. Kehrli (talk) 12:40, 26 October 2010 (UTC)

In response to Kehrli: The point was to present both sides of the Kendrick mass vs. Kendrick unit discussion in the two articles so that other editors could compare and comment. With your edits ([4], [5]), both articles have the same POV and a balanced discussion is now more difficult. Most importantly, you have failed to provide any scientific literature reference that defines a unit called a "kendrick" This reference ([6]) does not define a unit, it just uses the shorthand notation "Ke" that is not standard. A much more widely used shorthand for Kendrick mass is KM (e.g. [7], [8]doi:10.1016/j.atmosenv.2009.12.019). As stated above, the Kendrick mass scale is renormalization for convenience (it doesn't even have to be a renormalization to CH₂, for example see doi:10.1016/j.atmosenv.2009.12.019 where CH₂O is set to exactly 30 Da) and has never been called a unit. Wikipedia is not the place to define a kendrick unit and to do so, however reasonable and well-intentioned, is original research and POV pushing. --Kkmurray (talk) 15:36, 25 October 2010 (UTC)

Well, you suggested that in the merged article both sides should be presented. Then you presented the version that is in agreement with the conventions established by the IUPAP red book, the IUPAC green book, the ISO 31, and the International vocabulary of metrology only poorly. This gave a very biased view. Kehrli (talk) 12:40, 26 October 2010 (UTC)

Well said. I would suggest to Kehrli that his/her contributions could be welcomed if the scope, purpose and policies of wikipedia are respected. An open minded acceptance of input from other editors simply striving to maintain such purposes and policies such as Kkmurray may help.--Nick Y. (talk) 19:46, 25 October 2010 (UTC)

Kkmurray is pushing a terminology that is old, outdated, and faulty. I am pushing for a terminology that is in line with the conventions established by the IUPAP red book, the IUPAC green book, the ISO 31, and the International vocabulary of metrology. I do think that my approach is better suited to maintain purposes and policies of Wikipedia. Wikipedia is not a collection of errors of the past. Otherwise Wikipedia would have to state that the earth is flat, because that was the conventional view during 99% of human history. Kkmurray and Nick Y. are behaving like Flat Earthers. They seem not to realize that science and metrology is moving on. Kehrli (talk) 12:40, 26 October 2010 (UTC)

Just to give you one example on how faulty the terminology is that kkmurray is pushing. He claims:

$Kendrick~mass=SI~mass\times {\frac {14.00000}{14.01565}}$

With SI mass he means a mass in Daltons (or u), which means:

$SI~mass=n\times Da$

This, however, would make the Kendrick mass also be in Da.

$Kendrick~mass=n\times {\frac {14.00000}{14.01565}}\times Da$

However, this is not at all what Kkmurray is claiming in the remaining article. His formula contradicts his own opinion. And he does not even realize it. Kehrli (talk) 12:49, 26 October 2010 (UTC)

What you fail to realize is that your argument is not with me, it is with Alan Marshall and the editors of the Proceedings of the National Academy of Sciences. The equation you object to

$Kendrick~mass=SI~mass\times {\frac {14.00000}{14.01565}}$

is Equation 2 on page 18092 of doi:10.1073/pnas.0805069105 (now reference 3 in the article). The scientific literature has many other similar constructs for Kendrick mass

$Kendrick~mass=IUPAC~mass\times {\frac {14.00000}{14.01565}}~$ doi:10.1021/ar020177t, doi:10.1021/ac0355449, doi:10.1021/ac010560w, doi:10.1021/ac100556g

$KM=exact~measured~mass\times {\frac {14.00000}{14.01565}}~$ [9]

But I see your point and the use of SI mass in Marshall's PNAS paper is somewhat confusing. I would suggest that the "IUPAC mass" construct be used in the article since it is more widely used in the literature.

--Kkmurray (talk) 14:34, 26 October 2010 (UTC)

— Kehrli , — (continues after insertion below.)

Marshall's PNAS paper is more than "somewhat" confusing. It uses a terminology that is a disgrace to scientific communication. It should never have been published in this form. The peer review process failed completely. Your minor correction using IUPAC mass only helps marginally. IUPAC has many other mass units beside daltons. It has kg, g, tons. Therefore IUPAC mass could mean anything.

The fact that there are several different definitions out there that are only "similar" (an euphemism for contradicting) only shows the mess that people like Marshall are creating. You should not promote this messy jargon on Wikipedia. There are not two papers using the same terminology. Why not use the terminology of the last paper, which is the only paper using a consistent terminology?

And what you still do not understand: A MOLECULE DOES NOT CHANGE ITS MASS WHEN USING A DIFFERENT UNIT! You guys have a very basic misconception of physical quantities. In your way of thinking a person could loose weight when he would stop using a pound scale and start using a kg scale. THIS IS RIDICULOUS! Loosing weight is not that simple!

Look, we both agree that, let's say, a COO group has a mass that is not changing in time. It is a constant. Even if the earth would disappear, the mass of the COO group would stay the same. And if the solar system would collapse, the mass of the COO group would still remain the same. Hence, its mass is really, really, really constant. Agree? But in your formula (which I know is not yours, but you promote it) you claim that you can change this molecule's mass just by thinking in a different unit! How can you not realize that this formula is deeply flawed? It is rubbish! Even though it is from Marshall. Even though it went through a review process. It is absolute rubbish. And that is really easy to see. Just use your own brain. It is as easy to see as the faultiness of SI mass. Actually it is even easier: you don't even need to look up the SI booklet. All you need is your brain and some 7th grade math. Kehrli (talk) 22:05, 26 October 2010 (UTC)

Note also that Kendrick mass scaling is not limited to CH₂ as is indicated in these two articles:

"The Kendrick mass defect of points along a trend line represents a characteristic difference in the elemental formula (e.g., CH₂, COO, H₂, H₂O, etc.). If we label these trendline variations as F, then the following equations can be used to define the Kendrick mass defect for any F trendline."

$Kendrick~mass~(F)=(observed~mass)\times {\frac {nominal~mass~F}{exact~mass~F}}~$ doi:10.1021/ac034415p

... "Other normalizing units (e.g., F, H₂, H₂O, and O) can be selected for Kendrick mass defect analysis and applied to data lying along the respective lines."doi:10.1021/ac034415p

and

"Any combination of atoms can serve as the base for calculating Kendrick mass (KM). The Kendrick mass defect (KMD) is then defined as the difference between the nominal mass and KM. For example, if formaldehyde is used as the base, KM_CH2O and KMD_CH2O are obtained by setting the molar mass of CH₂O to exactly 30 amu [sic!]."doi:10.1016/j.atmosenv.2009.12.019

$KM_{CH_{2}O}=mass\times {\frac {nominal~mass_{CH_{2}O}}{mass_{CH_{2}O}}}~$" doi:10.1016/j.atmosenv.2009.12.019

These two works are completely at odds with your proposed unit "kendrick" since the Kendrick scaling factor for each functional group is different.

--Kkmurray (talk) 14:34, 26 October 2010 (UTC)

— Kehrli , — (continues after insertion below.)

Kermit, here you actually have a good point. It is the first valid point that you made. Congratulations! Here is my answer: There is no such thing as "scaling a unit" without creating a new unit. The kg happens to be a scaling of the Da by the Avogadro constant. It thereby does not become unitless. It also does not keep the same unit Da (as is claimed by many other chemists, e.g. in the textbook of Jürgen Gross who btw uses a different Kendrick equation than Marshall). It becomes a kg. Yes - you would require a new unit for each of these groups. I have not chosen that road. These other "scalings" were probably not anticipated by Kendrick. He is not to blame when other people misuse his terminology. I don't like this either. This is why I have the section on the equivalence relation (modulo function) in my Kendrick (unit) article. This would be the only consistent way to avoid creating new units. I would prefer that. Unfortunately Kendrick did not take that road. He could have spared us a lot of troubles (and units). :-) Kehrli (talk) 22:05, 26 October 2010 (UTC)

You say "I am pushing for a terminology" but that is exactly what you should not be doing. Wikipedia is not a forum, it is not a place for your opinion, and it is not a scientific journal. I agree with Nick Y that your contributions are valuable and welcomed when they fall within Wikipedia guidelines. I hope that we can have a good faith effort to improve this article.

--Kkmurray (talk) 14:34, 26 October 2010 (UTC)

I am pushing for the terminology that is the consensus of IUPAP red book, the IUPAC green book, the ISO 31, and the International vocabulary of metrology. I am not pushing for my opinion, which is different from the Kendrick unit. You are pushing the faulty terminology used in faulty PAPERS of a fringe group in a fringe field of chemistry. I am pushing a consensus that represents easily 100'000 times more people than yours (VIM includes all trade and commerce). A consensus that was peer reviewed by approx. 1000 times more reviewers than your handful of papers that are so faulty that one has to wonder whether they were reviewed at all. And by whom. Kehrli (talk) 20:11, 26 October 2010 (UTC)

Just to expand on Kkmurray's point and hopefully clarify for Kherli why his/her current efforts fall under NOT. The synthesis of two or more elements, be they standards, papers, stated opinions of respected authorities etc. to reach a logical conclusion that produces a new statement of fact, a new standard or a new interpretation is original research and outside the scope of wikipedia. This is true no matter how logical, truthful, useful or internally consistent the resulting statement is. This is distinct from summary where multiple sources are combined in novel language to briefly explain the whole without contributing any novel ideas or interpretations of the whole. --Nick Y. (talk) 15:57, 26 October 2010 (UTC)

Nick: Kermit and you have a systematic bias to chemistry in general and mass spectrometry in special. You guys think Wikipedia should be swamped with faulty mass spec jargon that no one else understands because you can find this jargon in some poorly reviewed papers in the field of mass spectrometry. Wikipedia is not a mass spec project. You should keep to the wider consensus terminology as it is explained in the IUPAP red book, the IUPAC green book, the ISO 31, and the International vocabulary of metrology. You claim that I am doing synthesis. Not true. Each one of these books alone is sufficient to prove what is wrong in your jargon. Kehrli (talk) 20:11, 26 October 2010 (UTC)

If the IUPAP red book, the IUPAC green book, the ISO 31, or the International vocabulary of metrology define the kendrick, please provide a cite. I'm fairly certain that there isn't one. Analytical Chemistry, Proceedings of the National Academy of Sciences and Accounts of Chemical Research are not fringe journals, but I take it from your dismissal of them that you agree that they are inconsistent with your position on the kendrick as a unit. I really don't think that your position will stand and I hope that you reconsider it. --Kkmurray (talk) 20:48, 26 October 2010 (UTC)

Kermit: the IUPAP red book, the IUPAC green book, the ISO 31, or the International vocabulary of metrology define what physical quantities and units are and how they are handled. Hence they define how a mass and therefore the kendrick mass scale must be handled. Compare this to a law book where it says how traffic crossings must be designed, how priority rights are handled, what signs should be used and what they mean. You won't find the names of specific crossing in a law book, but the law book still applies to specific crossings. Kehrli (talk) 14:18, 27 October 2010 (UTC)

I did not say that those journals are fringe journals! I said they address a fringe group (in the larger scale of schemes) and that you cite faulty papers. With all due respect: a paper that addresses a mass measured in daltons as "SI mass" is faulty and extremely poorly reviewed. A paper that claims esoteric effects like a change of mass just by thinking in different units is incredibly poorly reviewed. Such a paper is a disgrace for science. In the long term, science will loose all its credibility with papers like that. Kehrli (talk) 14:18, 27 October 2010 (UTC)

Please understand that I am not defending my position on the Kendrick mass. I am defending the position of the consensus established by the IUPAP red book, the IUPAC green book, the ISO 31, or the International vocabulary of metrology. My personal postition on the Kendrick mass unit is still different. I won't even mention it here because it is irrelevant for this discussion. Kehrli (talk) 14:18, 27 October 2010 (UTC)

• Summary: The term Kendrick mass refers to a rescaling of the standard atomic mass scale to zero the mass defect of a chosen moeity in limited and very specific situations in the field of mass spectrometry. It is neither formally defined nor recognized as a unit. It is sometimes informally used in place of units or without units but indicated in some other way. Although many such informal shorthands are used throughout science they do not conform to the widely accepted principles and standards set forth in formal documents regarding units and notations.

• Synthesis: The term Kendrick mass has sometimes been used in a manner consistent with being a unit and the IUPAP red book, the IUPAC green book, the ISO 31 state that all such uses must be formally defined and conform to certain standards. Thus, it is necessary to reconcile this by conforming this previously inconsistent usage to the standards of metrology here in order to properly define the Kendrick unit and clarify its future usage.

Both of these statements are truthful. One reflects the world as it currently is. The other reconciles the inconsistencies and synthesizes a more internally consistent and elegant solution. The synthesis statement is however NOT within the purpose or scope of Wikipedia, nor do I believe a very important subject to be addressing even in the proper context. Go write an opinion article and submit it to JASMS.--Nick Y. (talk) 13:18, 27 October 2010 (UTC)

Nick, I wish the truth were that simple as in your summary. Fact is: every paper has its own definition on what your "scaling" is. There is no majority view. Some of these definitions make some sense. Some make no sense at all. Kermit picked the one definition that makes the least sense. It talks about scaling, which we all understand is applying a different mass scale (which is equivalent to using a different unit) to a mass quantities. However, in the formula they do exactly the opposite: they use the same mass scale and change the quantity. It is insane. Some other papers get it right. The one I picked has a consistent definition of the scaling and it makes sense. So your summary is not accurate at all.

Your Synthesis is also incorrect. The main criteria on Wikipedia are neutrality and verifiability. We have ten different definitions of the Kendrick mass scale. I picked the one that is most verifiable: it is published in a paper (secondary source AND it is in line with the IUPAP red book, AND the IUPAC green book, AND the ISO 31, AND the International vocabulary of metrology (all tertiary sources). It has the most and the best sources. Kermit however picked the one definition that has one single source and that even he himself had to admit uses confusing terminology which is not only not verifiable but which is verifiably wrong. My article is also more neutral, because I did not pick only one of of the definitions, I picked two and discussed both in detail. I showed that the second one contains terminology that is FERIFIABLY not in line with the metrologic consensus of the International vocabulary of metrology. I do not do synthesis, I just have more and better sources.

This is it exactly. The synthesis happens when one believes that the general principles stated in the Red Book/Green Book/ISO 31 "define how a mass and therefore the kendrick mass scale must be handled" even though they do not define or even mention a kendrick unit. This synthesis is then used to reject peer reviewed publications in respected journals such as the Proceedings of the National Academy of Science as "faulty and extremely poorly reviewed" and "a disgrace for science" because they are at odds with the synthesis. --Kkmurray (talk) 16:58, 27 October 2010 (UTC)

Kermit, there is no synthesis. You seem to forget that the article I am backing is based on the most recent and the most relevant paper in the field of our discussion (primary source). And, in ADDITION, it verifiably agrees with the general principles of the IUPAP red book, AND the IUPAC green book, AND the ISO 31, AND the International vocabulary of metrology. There is no synthesis, these are all independent tertiary sources. You don't have a single tertiary source. My article simply has the most and the best sources and therefore is much better verifiable, which is a key requirement on Wikipedia.

I am not using a synthesis to criticize the journal, I am using the fact that the authors used terrible terminology (like SI-mass for a mass in Da even though the Da is a unit outside the SI), erroneous math (like changing the mass of a molecule instead of changing the mass scale, what they claimed to be doing), and many more terrible errors to judge a paper. All these errors were not caught in the review process, which is absolutely frightening. It shows that the review process for this paper was completely dysfunctional. I just can hope for this journal that this is not their normal procedure.

The fact that a professor is backing such a poor definition on Wikipedia (a definition that is full of verifiable errors, has only one source, and contradicts all tertiary sources) is not very encouraging for this field of science either.

Look, you guys are on a rampage. Cool it down a notch. Use your brain and don't get carried away defending stuff that even you understand is wrong. You need to keep a NPOV. Don't get your personal feelings involved. Kehrli (talk) 00:16, 28 October 2010 (UTC)

There are ten different definitions because there is actually none. A proper summary could include the fact that definitions vary and are inconsistent with other sources. I would ask you to write a summary here in this space. Feel free to include strong language, perhaps even POV, but do not synthesize anything new. This means that the concepts implied in "Thus" and "Therefore" are not within the scope. Nothing needs to be resolved or made logical. It might be reasonable to point out that something is unresolved or illogical but not to lead the reader down any logical path suggesting a resolution. How about we all try that, that is write in Kherli's voice his summary statement. It will be filled with POV and will still be an issue but at least we can remove synthesis.--Nick Y. (talk) 15:49, 28 October 2010 (UTC)

Summary statement

Summary Statement for Kherli The Kendrick mass is a poorly defined rescaling of the normal molecular mass scale to zero the mass defect of an arbitrary chemical formula. There is no agreed upon definition and many sources define it very differently. It sometimes has an appearance of being a unit of measure; however all current definitions are inconsistent with the standards normally applied to units and no standards organization has ever endorsed such a unit.--Nick Y. (talk) 15:57, 28 October 2010 (UTC)

Nick, you are getting very close except for one small mistake: there is a recent publication which got the definition right. Their definition is consistent in itself. That is already a big achievement which I have not seen anywhere else so far. In addition it is consistent with the general principles of the IUPAP red book, AND the IUPAC green book, AND the ISO 31, AND the International vocabulary of metrology. In other words: this definition is by far superior and better sourced than anything else. This is why I think we should use it on Wikipedia. In order to be neutral we should also present the other definitions, and we should mention their shortcomings in an objective way.

Now, when I read it again, I don't like your first sentence because of the term "rescaling" which is ill defined. Also, to my knowledge, Kendrick only applied his new Kendrick mass scale for the group CH2, not any group. This was only done later by other authors.

Then another point: it is true that no standard organization ever endorsed a Kendrick unit or Kendrick scale. However, this is a mute point. The International vocabulary of metrology states that units are created "by convention". They just have to match some well specified requirements. For me that means units can be created at hoc, as long as some people convene and agree with each other. However, the units must be created according to strict rules. It is like a traffic regulations: the law does not endorse cars. It just sets requirements that a car must fulfill. Kehrli (talk) 00:28, 29 October 2010 (UTC)

Summary Statement for Nick The "Kendrick mass scale" is a currently poorly defined scale of mass, used to indicate the normal molecular mass, and to zero the mass defect of the 12CH2 group. There is no agreed upon definition and many sources define it very differently. The term "Kendrick rescaling" has been used to generalize this method for other chemical groups. The term "Kendrick mass" has often been used to mean a mass measured in the "Kendrick mass scale". "Kendrick mass units" have sometimes been used as a unit of measure; however all definitions (except for one recent attempt) are inconsistent with the standards normally applied to units and no standards organization has ever defined or endorsed such a unit. Kehrli (talk) 00:28, 29 October 2010 (UTC)

Just to be clear, the recent publication that User:Kehrli cites as definitive in establishing the kendrick unit states (Junninen, H.; Ehn, M.; Petäjä, T.; Luosujärvi, L.; Kotiaho, T.; Kostiainen, R.; Rohner, U.; Gonin, M.; Fuhrer, K. (2010). "A high-resolution mass spectrometer to measure atmospheric ion composition". Atmospheric Measurement Techniques. 3: 1039. doi:10.5194/amt-3-1039-2010.{{cite journal}}: CS1 maint: unflagged free DOI (link))

"Members of hydrocarbon homologous series differ from each other by a mass of CH₂ (14.01565Da). Thus, it is possible to recognise patterns of compounds belonging to the same family by finding a series of peaks differing by 14.01565 Th. It simplifies the interpretation of a complex organic mass spectrum by expressing the mass of hydrocarbon molecules in Kendrick units (where m(¹²CH₂)=14 Ke) instead of Dalton (where m(¹²C)=12 Da) (Kendrick, 1963)."

I would have to disagree that this publication provides any sort of definition of Kendrick unit as opposed to a description of the Kendrick mass scaling process.

--Kkmurray (talk) 03:00, 29 October 2010 (UTC)

— Kehrli , — (continues after insertion below.)

In all due respect: m(¹²CH₂)=14 Ke is a perfect definition of the Kendrick mass unit Ke. It is short, concise, consistent and in line with the general principles of the IUPAP red book, AND the IUPAC green book, AND the ISO 31, AND the International vocabulary of metrology. Kehrli (talk) 13:05, 29 October 2010 (UTC)

Compare this to a recent publication from Marshall's group that doesn't mention units or a symbol but is otherwise identical (Marshall, Alan G.; Rodgers, Ryan P. (2004). "Petroleomics:  the Next Grand Challenge for Chemical Analysis". Accounts of Chemical Research. 37: 53. doi:10.1021/ar020177t. {{cite journal}}: no-break space character in |title= at position 14 (help))

"We previously noted that the repeating mass (CH₂) for a carbon distribution series is 14.01565 Da. It is particularly useful to rescale the mass spectrum from the usual IUPAC mass scale (based on the ¹²C atomic mass as exactly 12 Da) to the “Kendrick” mass scale: Kendrick mass = IUPAC mass × (14/14.01565). The Kendrick scale effectively converts the mass of CH₂ from 14.01565 to exactly 14.00000."

-- Kkmurray (talk) 03:00, 29 October 2010 (UTC)

— Kehrli , — (continues after insertion below.)

There are about 4 serious error in this definition. Errors that are so serious that it is a disgrace to science. —Preceding unsigned comment added by Kehrli (talk • contribs) 13:05, 29 October 2010 (UTC)

Here's a work that broadens the concept of scaling to any functional group (Junninen, H.; Ehn, M.; Petäjä, T.; Luosujärvi, L.; Kotiaho, T.; Kostiainen, R.; Rohner, U.; Gonin, M.; Fuhrer, K. (2010). "A high-resolution mass spectrometer to measure atmospheric ion composition". Atmospheric Measurement Techniques. 3: 1039. doi:10.5194/amt-3-1039-2010.{{cite journal}}: CS1 maint: unflagged free DOI (link))

"The standard IUPAC scale sets the atomic mass of ¹²C to exactly 12 amu. Kendrick redefined the mass scale by choosing a different base, most commonly by setting the molar mass of CH₂ group to exactly 14 amu (Kendrick, 1963). Any combination of atoms can serve as the base for calculating Kendrick mass (KM). The Kendrick mass defect (KMD) is then defined as the difference between the nominal mass and KM. For example, if formaldehyde is used as the base, KM_CH2O and KMD_CH2O are obtained by setting the molar mass of CH₂O to exactly 30 amu."

The Atmospheric Environment article blows a pretty big hole in User:Kehrli's argument that 1 Da is exactly 0.99888 Ke;[10] since there will be a different Kendrick scaling factor and different Kendrick "unit" for every repeat unit (CH₂, CH₂O, etc). Not only that, but they use KM instead of Ke as an abbreviation of Kendrick mass (or "unit"). There seems to be no standard notation.

Here's another publication that says that any repeat unit can be used in a Kendrick-type mass scaling (Kim, Sunghwan; Kramer, Robert W.; Hatcher, Patrick G. (2003). "Graphical Method for Analysis of Ultrahigh-Resolution Broadband Mass Spectra of Natural Organic Matter, the Van Krevelen Diagram". Analytical Chemistry. 75: 5336. doi:10.1021/ac034415p.)

"The Kendrick mass defect of points along a trend line represents a characteristic difference in the elemental formula (e.g., CH₂, COO, H₂, H₂O, etc.). If we label these trendline variations as F, then the following equations can be used to define the Kendrick mass defect for any F trendline: Kendrick mass (F) = observed mass × (nominal mass of F)/(exact mass of F)"

So there are two journal articles in Analytical Chemistry and Atmospheric Environment published in 2003 and 2010 that by implication negate the claim that 1 Da is exactly 0.99888 Ke and the existence of a unique Kendrick "unit".

Here's a recent paper from from U.C. Davis (Lerno, Larry A.; German, J. Bruce; Lebrilla, Carlito B. (2010). "Method for the Identification of Lipid Classes Based on Referenced Kendrick Mass Analysis". Analytical Chemistry. 82: 4236. doi:10.1021/ac100556g.)

"The monoisotopic masses belonging to lipids were converted from IUPAC mass conventions (¹²C ) 12.0000) to the Kendrick mass scale in which the methylene unit defines the mass scale and is set to 14.0000."

The Davis group uses "Kendrick mass scale" exclusively and doesn't mention unit or units in conjunction with the Kendrick analysis at all.

--Kkmurray (talk) 03:00, 29 October 2010 (UTC)

Kermit, all you have shown so far is that there are indeed a large number of different and mutually incompatible definitions. This is exactly what Nick and I agreed on. We all know by now that all these definitions contradict each other. Any definition can be used to "blow a big hole" in any other. We know that. Your comment is old news and not useful. It seems that you plan to prevent a consensus in order to push your personal point of view. Please cool down and engage in a constructive discussion, as Nick and I are is trying to.

The good thing about your post is that you showed nicely how the definitions vary and disprove each other even when coming from the same group. Marshall has definitions which are not compatible and contradict each other. The group of Junninen offered the best definition in one paper, but also the worst definition in another paper. They use the completely outdated unit "amu", use a wrong definition of the "amu" (¹²C = 12 amu instead of m(O) = 16 amu), and they redefine the amu at will. This is absolutely horrible.

The important fact is that there is only one definition that is in agreement with the wider consensus of the IUPAP red book, AND the IUPAC green book, AND the ISO 31, AND the International vocabulary of metrology. It is the definition: m(¹²CH₂)=14 Ke. It therefore is the only definition with good sources. All others fail the verifiability test.

I can go through every definition and tell you where it is contradicting the metrology consensus of the International vocabulary of metrology. However, I did that already many times and you always ignore the arguments.

There is just one thing I would like to mention which you seem not to fully comprehend yet: rescaling a unit is absolutely not acceptable. It's against the law. In some publications from the Marshall group they start with m(¹²C) = 12 Da and then they "rescale" to m(¹²CH₂) = 14 Da. It is absolutely not ok to "rescale" an official unit. Imagine your butcher would some day give you only half the amount of meat than before for the same money. When you ask him what's going on he would answer: "I just rescaled the pound to half its previous value". It is called fraud. He would go to prison for that. Only professors of Chemistry seem to get away with this kind of frivolous metrology. Kehrli (talk) 13:05, 29 October 2010 (UTC)

I de-interspersed your comments so that my comment is a contiguous block with my sig at the bottom. I think that this is the talk page standard.

I don't mean to derail the useful discussion that you and Nick are having, but I think that it is good to have the definitions from the scientific literature at hand to help us maintain WP:VERIFY principles. I am also interested to hear your comments on specific literature definitions and how they should be integrated into the article using a neutral point of view. Specifically, I think that you need to address the errors that you find in Marshall's definition. His group is leading the way in "Petroleomics" and will therefore have the greatest weight (per WP:VERIFY) in determining the way that Kendrick mass is used. --Kkmurray (talk) 13:33, 29 October 2010 (UTC)

(Comments re-interspersed per WP:SIGCLEAN; it is OK to interrupt but authorship should be indicated. --Kkmurray (talk) 15:59, 29 October 2010 (UTC) )

Thanks for reorganizing the comments. It is surprising to see how somebody that gives so much attention to writing style on Wikipeda, can give so little attention to metrology in science. It blows my mind. I do not mean that in a sarcastic way. I think in the end both are a matter of aesthetics. I am quite sure that once you understand the concepts of metrology you will become their most forceful defender.

Marshall is great in petroleomics, and he is probably one of the best mass spectrometrists. But he really, really sucks in metrology. Compare this to Dale Earnhardt: he certainly was a good car racer (MS user). He probably was not near as good in building cars (MS builder). And it is well possible that he had way above average number of speeding tickets and traffic violations (MS metrology). What I mean to say: you should not conclude from the fact that Marshall is great in Petroleomics that he is also good in MS terminology.

I very much support your attempt to maintain WP:VERIFY principles. However, we already know that all primary sources contradict each other. Therefore they won't help us. We have to turn to secondary sources and tertiary sources which are defined as:

• Secondary sources involve generalization, analysis, synthesis, interpretation, or evaluation of the original information.
• A tertiary source may thus be understood as a selection, distillation, summary or compilation of primary sources, secondary sources, or both

So let's start with a tertiary source, the VIM [11]. I will now guide you through a couple of steps to show you the wider consensus on how the Kendrick mass should be treated. (In this process we will see that the term Kendrick mass itself is not quite kosher.)

• quantity: property of a phenomenon, body, or substance, where the property has a magnitude that can be expressed as a number and a reference

mass is a quantity

hence, Kendrick mass is also a quantity (since it is a mass)

• Quantities of the same kind within a given system of quantities have the same quantity dimension.

All masses are quantities of the same kind

Mass is a base quantity and its dimension is called M

Hence a mass is never dimensionless

Hence a mass always needs a unit

About 50% of the definitions fail this step. They include statements like: The Kendrick mass of ¹²CH₂ is 14.000. Such a statement is verifiably not in line with the VIM. This is a serious problem. Metrology is the science of measuring. If a measuring process is verifiably not in line with the VIM then it is most probably fair to say it is verifiably wrong. Let us continue:

we need a unit for the Kendrick mass. Which one should it be? In the literature we find basically two suggestion: Kendrick mass unit (also mentioned by Marshall, by the way) and and Kendrick unit. Either one is fine with me because they designate the same. It is like "kg mass unit" and "kg unit". Both are common.

• measurement unit, unit of measurement, unit: real scalar quantity, defined and adopted by convention, with which any other quantity of the same kind can be compared to express the ratio of the two quantities as a number
• Measurement units are designated by conventionally assigned names and symbols.

We need names and symbols for the Kendrick mass unit. The following symbols have been proposed: Da, amu, Ke.

The amu is now discontinued by convention and replaced by the u. Therefore we can eliminate it.

We still have the symbols Da and Ke with the respective names dalton and kendrick.

Dalton is much more common and seems to win the race.

• quantity calculus: set of mathematical rules and operations applied to quantities other than ordinal quantities

now let us look at the "definition" in the article Kendrick mass

Kendrick mass = SI mass * 14.00000/14.01565

This is a quantity equation. There is something fundamentally wrong with this equation. According to this equation a molecule gets more massive when measured in Da than when measured in the Kendrick mass units. This does not make sense. The correct equation is:

Kendrick mass = SI mass = m(M)

The molecule M has the same mass independent on the units. There is only one mass, m. It can have different units, but its value is not changed by this. (Only the numerical value is changed to compensate for the difference in the unit). The terms Kendrick mass and SI mass are not necessary and even somewhat confusing. The VIM says:

• In quantity calculus, quantity equations are preferred to numerical value equations because quantity equations are independent of the choice of measurement units, whereas numerical value equations are not (see ISO 31-0:1992, 2.2.2)

Now let's check this equation with the example M = ¹²CH₂ where we know what is supposed to happen. First we assume the Kendrick mass unit is Da:

m(¹²CH₂) = 14 Da = 14.01565 Da

14 Da = 14.01565 Da

14 = 14.01565

This is obviously wrong. This means the Da cannot be the Kendrick mass unit. Let's try with the Ke

m(¹²CH₂) = 14 Ke = 14.01565 Da

1 Ke = 14.01565/14 Da

Now it makes sense. The deeper interpretation of what we just did is: The phrase "scaling the mass" is wrong. It is illogical to scale a mass as it is illegal to scale a unit (as I showed with the butcher example). It is, however, absolutely legal to define a new unit and indicate a conversion factor between the old unit and the new unit. The VIM says:

• conversion factor between units: ratio of two measurement units for quantities of the same kind

So we have used the VIM as a filter of all the terms and terminology used in the papers about the Kendrick analysis. We found that many terms used in these papers are not appropriate. Among them "mass scaling", "unit scaling", "Kendrick mass", "SI mass", "dimensionless mass", Da as a Kendrick mass unit. All those terms are confusing at best, verifiable wrong at worst. Terms that are verifiable are: "conversion factor between units", "independent on units", mass quantity, numerical factor of a quantity, unit = reference quantity, and so on. These are the terms that should be used in a definition of Kendrick analysis. There is, unfortunately, only one paper that used them. And back to your question:

Specifically, I think that you need to address the errors that you find in Marshall's definition.

I hope that I have shown you that Marshall, however good a mass spectrometrist he may be, is using crappy terminology and fuzzy math to communicate his great results. Kehrli (talk) 21:43, 29 October 2010 (UTC)

Kendrick Analysis 101

There are three different methods to do a Kendrick analysis:

Trend line method

The simplest way is to produce a graph where each molecule M is arranged according to its mass m(M) and its mass excess/defect ∆m(M) = m(M) - integer[m(M)]. When expressing the mass m in daltons, (in metrology terms: [m] = Da) this aligns all homologous molecules on trend lines whose slope depends on the "building block" of the molecules. The disadvantage of this method is that the offsets from sloped trendlines are difficult to read. The advantage is that no new units have to be introduced and that it works for all "building block" molecules.

Kendrick method

Kendrick realized that by using a mass scale with units equal to the mass of the building blocks, the trend lines would become horizontal for all homologous families of this "building block". This simplifies somewhat the reading of the mass defect. However, it requires a new mass scale and thereby a new unit for each building block as well as a conversion of each molecule mass into this unit.

CH₂ Modulo method

Math has a tool called modular arithmetic that can reveal the same homologous relation using the modulo operation.

A ~ B (mod CH₂)

The above statement is read: "A is modulo CH₂ equivalent to B." Or, when considering the mass of the molecules A and B:

m(A) ~ m(B) (mod m(CH₂))

"A has the same modulo CH₂ mass as B."

The Kendrick mass defect of a molecule M, Δm(M), would be expressed as the remainder r:

Δm(M) = r = m(M) mod m(CH₂)

If the modulo operation nor the remainder operation are defined

Δm(M) = m(M) - m(CH₂)·round(m(M)/m(CH₂))

This method has all advantages of the previous methods: it works with any building blocks, does not require new units, and it produces horizontal lines in a Kendrick plot.

Kendrick modulo method

Closer inspection reveals that above modulo method is not equivalent to the previous two methods. The modulo method above uses m(CH₂) as the modulus whereas the Kendrick method effectively uses m(CH₂)/14 as the modulus. Thereby the range of the reminders shrinks from 14 Da to a range of 1 Da, effectively wrapping the reminders into a constrained space. Some groups have found that this leads to overcrowding with complex samples and therefore "unfolded" the effect of the Kendrick modulus by creating 14 versions of Kendrick plots, thereby recreating the properties of CH₂ modulo method. (Hsu, C. S.; Qian, K. N.; Chen, Y. N. C. Anal. Chim. Acta 1992, 264, 79-89. http://dx.doi.org/10.1016/0003-2670(92)85299-L and Alain Reinhardt, Christian Emmenegger, Bertran Gerrits, Christian Panse, Josef Dommen, Urs Baltensperger, Renato Zenobi, and Markus Kalberer; Anal. Chem. 2007, 79, 4074-4082)

The Kehrli plot

It is not exactly clear why Kendrick choose a m(CH₂)/14 modulus instead of a m(CH₂) modulus. It may be for visualization reasons. For low masses the mass defects are quite small. Therefore all molecules would be very close to the integer mass lines when using the m(CH₂) modulus in a Kendrick type plot. In this case it would be interesting to see a plot with the m(CH₂)/14 reminder (= Kendrick mass defect) on one axis (y-axis) and the m(CH₂) reminder on the x-axis. This plot could be more informative than the traditional Kendrick plot. Both plots would just be different views from the 3D data structure where each molecule would be plotted in a 3D space with mass, m(CH₂) reminder and m(CH₂)/14 reminder as axis.