Talk:Volume fraction

Measurability

Is it a measurable quantity in non-ideal mixtures? It seems that is only calculable by knowing mass or amount fraction and densities of pure components.--188.26.22.131 (talk) 10:47, 9 September 2013 (UTC)

I don't think you can obtain the volume fraction once the non-ideal components have been mixed. Therefore, "volume fraction" is quite useless for practical purposes.--RolfSander (talk) 13:56, 10 September 2013 (UTC)

Although practically useless, it seems frequently used for instance in beer alcoholic content. What is the real meaning of the alcohol by volume concept? Also what is the real volume of a component in mixture?--188.26.22.131 (talk) 11:27, 16 September 2013 (UTC)

Different index

A question about the index to V-i(j) arises whether or not should be different in the denominator compared to that in numerator of the fraction. I think the index should be identical because the volume of a component is divided by the sum of volumes of all components before mixing.--188.26.22.131 (talk) 15:30, 4 March 2014 (UTC)

It's better to use a different letter, since it is a different index in any case. The one in the denominator is summed over and thus has no meaning outside the sum. Using the same letter in the nominator would make the wrong impression that V_i is part of the sum. — HHHIPPO 19:20, 4 March 2014 (UTC)

It's not a wrong impression, V_i is actually included in the sum thus there is no need of different indexes.--188.26.22.131 (talk) 15:23, 5 March 2014 (UTC)

I meant the V in the nominator. There's no need for identical indices either, so we can keep it the way that's easier to read. — HHHIPPO 18:11, 5 March 2014 (UTC)

Using two indexes would create confusion. Since V_i is part of the sum which appears in the denominator a single index i is enough.--188.26.22.131 (talk) 10:30, 10 March 2014 (UTC)

I don't see how that can cause more confusion than using the same letter for different things. Frankly, I don't think I can help you any more here. You asked a question, I wrote what I think about it and why, and you contradict by making unsubstantiated assertions. If you are indeed interested in other people's opinions, I'd suggest you ask at WT:WikiProject Mathematics. — HHHIPPO 19:42, 10 March 2014 (UTC)

I agree with HHHIPPO that using a different index is less confusing. Regarding correctness, I'm not sure (I'm a chemist, not a mathematician). To avoid our problem completely, I suggest to revert to the version from 2014-01-27. There we simply had V in the denominator to represent the total volume.--RolfSander (talk) 18:49, 11 March 2014 (UTC)

I don't understand what confusion is involved if the same index is used. Nevertheless, I'll ask at WT:WikiProject Mathematics about mathematical correcteness of the notation.--188.26.22.131 (talk) 10:17, 17 March 2014 (UTC)

According to the rules of formal languages (both in math and in programming) the running index is local to the sum, and may be replaced with any other index at will, no matter whether or not the same letter appears somewhere outside the sum. Thus, all versions are formally correct. But it does not mean that they are equally good informally. Maybe not; you decide. Boris Tsirelson (talk) 10:43, 17 March 2014 (UTC)

If one want to consider $\phi _{1}$, one has simply to substitute j by 1 in

$\phi _{j}={\frac {V_{j}}{\sum _{i}V_{i}}}$

On the other hand, although

$\phi _{i}={\frac {V_{i}}{\sum _{i}V_{i}}}$

is formally correct, a good mathematical experience is needed for understanding that only the index in the numerator has to be substituted by 1. Thus, having the same index in the numerator and in the denominator is confusing for most readers. D.Lazard (talk) 11:55, 17 March 2014 (UTC)

Certainly the notation ${\dfrac {V_{i}}{\sum _{i}V_{i}}}$ uses the same letter, i, for two different things. The i in the numerator stays fixed while the i  in the denominator runs through a list of values. This kind of thing actually does leead to mistakes by students in some contexts; I've seen it in papers I've graded. Michael Hardy (talk) 17:50, 18 March 2014 (UTC)

In some cases

$V_{j}|_{j=1}$

may be different from

$V_{i}|_{i=1}$

It's an abuse of notation, but it's been known to happen. But, as I am an experienced mathematician, I'm not the one to comment about perceived confusion. — Arthur Rubin (talk) 02:24, 19 March 2014 (UTC)

If I saw that in a paper I would be very upset with the author, and would only continue reading if I got the impression I was reading unpublished shorthand, otherwise I wouldn't expect for anything else they say to be clear. It's writing for insiders eyes only. ᛭ LokiClock (talk) 14:15, 19 March 2014 (UTC)

While I understand, but don't necessarily agree with, the formal correctness of the expression (it is a convention after all), I do recognize bad notational choices. Having the same symbol represent different things in the same expression is clearly such a bad choice. The fact that experienced readers can correctly parse the expression is not a justification for its use. Bill Cherowitzo (talk) 17:10, 19 March 2014 (UTC)

Another thought. There is a difference between formally correct and correct. In the current situation, if there were say three components (N = 3), it would be "formally correct" to write $\phi _{5}={\frac {V_{5}}{V_{1}+V_{2}+V_{3}}}$, but this is meaningless (i.e., wrong) in the current context. The claim made above that $V_{i}$ was one of the summands in the denominator does not follow from any rule of correct formula construction, as this example illustrates. The "error" in thinking that it was is caused by using the same symbol to mean different things. (Oh, by the way, the current version should be fixed to indicate that j = 1, ..., N.) Bill Cherowitzo (talk) 20:04, 19 March 2014 (UTC)

The last aspect involving V₅ outside the range of index from the denominator is interesting when considering the formation of multicomponent mixtures like that with at least 5 components from binary and ternary mixtures where V₅ is zero in the submixture not containing it, but non-zero in the final mixture.--213.233.84.33 (talk) 00:26, 4 February 2018 (UTC)

Merger

Volume percent into volume fraction; Mass percent and Mole fraction already readirect to Mass fraction and Mole fraction, respectively. Fgnievinski (talk) 18:14, 31 January 2015 (UTC)

• Agree with the proposed merge. Wayne Jayes (talk) 06:58, 16 October 2015 (UTC)
• Agree with the proposed merge. RolfSander (talk) 09:32, 16 October 2015 (UTC)

Yeah, except that Volume percent is typically concentration, not fraction (that difference does not exist for mass fraction). — Preceding unsigned comment added by 93.199.252.120 (talk) 18:56, 1 November 2017 (UTC)

One can notice a discrepancy between the volume percent and volume fraction.--109.166.132.159 (talk) 23:12, 20 August 2019 (UTC)

%vol

From the NIST Guide to SI, sec. 7.10.2 %, percentage by, fraction:

Because the symbol % represents simply a number, it is not meaningful to attach information to it (see Sec. 7.4). One must therefore avoid using phrases such as “percentage by weight,” “percentage by mass,” “percentage by volume,” or “percentage by amount of substance.” Similarly, one must avoid writing, for example, “% (m/m),” “% (by weight),” “% (V/V),” “% (by volume),” or “% (mol/mol).” The preferred forms are “the mass fraction is 0.10,” or “the mass fraction is 10 %,” or “wB = 0.10,” or “wB =10 %” (wB is the quantity symbol for mass fraction of B—see Sec. 8.6.10); “the volume fraction is 0.35,” or “the volume fraction is 35 %,” or “ φB = 0.35,” or “φB = 35 %” (φB is the quantity symbol for volume fraction of B—see Sec. 8.6.6); and “the amount-of-substance fraction is 0.15,” or “the amount-of-substance fraction is 15 %,” or “xB = 0.15,” or “xB = 15 %.”

and sec 7.4 Unacceptability of attaching information to units:

When one gives the value of a quantity, it is incorrect to attach letters or other symbols to the unit in order to provide information about the quantity or its conditions of measurement. Instead, the letters or other symbols should be attached to the quantity. Example: V_max = 1000 V but not: V = 1000 V_max Note: V is a quantity symbol for potential difference. [and non-italic V is voltage unit.]

I intend to update the article accordingly. Fgnievinski (talk) 18:21, 31 January 2015 (UTC)

Regarding “percentage by weight,” “percentage by mass,” “percentage by volume,” or “percentage by amount of substance”: The articles should still mention these phrases, even while explaining why they are not preferred. As opposed to removing all trace of them. Reason: They are widely used, and Wikipedia covers all important aspects of a topic, even as it explains what the best practice is. Quercus solaris (talk) 00:35, 1 February 2015 (UTC)

Updating this article to reflect the US NIST recommendation is fine, saying presumably the % by ???? are deprecated. A reference to IUPAC may also be appropriate, at least it gives the article an international flavor. However I agree with user:Quercus solaris that wikipedia should mention both. As a by the by - a fraction is different from a percentage, ask any school kid. NIST and IUPAC logic seems more like nit-picking- % by weight is a dimensionless number derived by dividing one weight by another. Axiosaurus (talk) 19:03, 2 February 2015 (UTC)

It's a slippery slope when folks start attaching information to units (as in "fraction = x %vol" instead of "volume fraction = x %"), see, e.g., Decibel#Suffixes and reference values. Fgnievinski (talk) 23:29, 2 February 2015 (UTC)

Percent deviation from additivity

What is the quantitative expression of the relative volume difference associated to the verbal phrase +/_x % deviation (expansion or contraction) from the addivity of volumes in water ethanol or water salt/sugar solutions?

Could it be a fraction whose numerator include the difference between the volume of the mixture V and the volumes of the two components V1 and V2 and the denominator equals the sum V1+V2:

$\%\Delta V_{r}={\frac {V-(V_{1}+V_{2})}{V_{1}+V_{2}}}100$? or $\%\Delta V_{r}={\frac {V-(V_{1}+V_{2})}{V}}100$?

Which one of these two variants of this fraction which can be called relative volume difference are more appropiate?--85.121.32.1 (talk) 15:39, 6 May 2016 (UTC)

Link to apparent (molar) volume

The previous section above suggests the approaching of a link to volum apparent molar property in relation to the deviation from additivity.--82.137.11.8 (talk) 13:42, 17 October 2017 (UTC)

Section - Volume concentration

A section Volume concentration could be added to article, perhaps expanding the info at talk:Volume concentration with details from de:Volumenkonzentration.--109.166.132.159 (talk) 23:41, 20 August 2019 (UTC)

Expansion sounds good. Or maybe even convert Volume concentration to an actual article? But for expansion, it sounds like the topic is equal to the pre-existing § Volume percent section. DMacks (talk) 17:54, 21 August 2019 (UTC)

The content of the section Volume percent should be checked for consistency with volume fraction denominator. This section has been added by a doubtful merger of Volume percent proposed in a section above. It is not clear why the volume percent should have a different denominator than volume fraction which has a sum as denominator due to simplicity in calculation. Another source beside Chembuddy must be checked to verify the accuracy of definition of volume percent to see whether it has the same denominator as volume fraction or volume concentration.--109.166.132.159 (talk) 23:15, 21 August 2019 (UTC)

If the denominator of volume percent is the same with that of volume concentration, volume percent should redirect to volume concentration when it will be a distinct article.--109.166.132.159 (talk) 23:56, 21 August 2019 (UTC)

I added a direct ref for the denominator being the (mixed) solution volume when the term "concentration" is used. DMacks (talk) 18:59, 23 August 2019 (UTC)