Talk:Molar absorption coefficient

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Absorbance versus absorption[edit]

"It is an intrinsic property of the species; the actual absorbance of a sample is dependent on its thickness L and the concentration c of the species."

Should this actually say:?

"It is an intrinsic property of the species; the actual absorption of a sample is dependent on its thickness L and the concentration c of the species."

No, absorbance is fine, because it is a way to quantify absorption, and because the phrase refers to the distinct nature of absorbance and molar absorptivity, two different concepts that are often confused.--Nevermore78 01:29, 3 April 2006 (UTC)[reply]

Note that absorbance has a very specific technical definition. 128.146.32.223 (talk) 02:56, 2 September 2009 (UTC)[reply]

Thickness?[edit]

I've actually never used the term thickness before, should we perhaps use path length instead of thickness? Hmm. Article needs some work. Better put it on my to-do list.GreatMizuti 13:00, 3 October 2006 (UTC)[reply]

Done 84.92.241.186 14:15, 28 April 2007 (UTC)[reply]

Units?[edit]

Perhaps the units should also be listed on the main page, as is done with all other physics items listed in wiki? Mueschke

I made a separate paragraph for units neffk (talk) 14:10, 28 May 2009 (UTC)[reply]

Molar (decadic) absorption coefficient[edit]

IUPAC recommends that ε be called the molar (decadic) absorption coefficient. See [1], [2], and especially [3].
— DIV (128.250.204.118 08:20, 7 September 2007 (UTC))[reply]

This article should be appropriately changed. 128.146.32.223 (talk) 02:56, 2 September 2009 (UTC)[reply]

These links should be changed, the new IUPAC site don't have it. The new (old) links are: 10.2.1.3 Molecular spectroscopy, 10.3.5.2 Measuring techniques, and 11.2 Terms and symbols used in photochemistry and in light scattering. 148.234.94.14 (talk) 19:48, 10 March 2017 (UTC)[reply]

Convert between ε and E1%[edit]

Shouldn't ε and E1% be swapped in the conversion formula? It should rather be E1%=(ε*molecular weight)/10 and not vice versa. Sachoques (talk) 20:24, 4 June 2008 (UTC)[reply]

No, because the units don't work out that way. ε is in M^-1cm^-1, E1% in g^-1 L cm^-1, and molecular weight in g mol^-1: (mol/L)^-1cm^-1 = mol^-1 L cm^-1 = g^-1 L cm^-1 * g mol^-1 -- 99.153.134.31 (talk) 23:03, 14 September 2008 (UTC)[reply]

Err... actually, after thinking about it, I'm not sure what units E1% should have (absorbances should be unitless). The general principle holds, though. Since ε is per molar, you need to get the moles in the denominator of the other side. -- 99.153.134.31 (talk) 23:27, 14 September 2008 (UTC)[reply]

E1% is unitless, is the absorbance of a solution of 1% protein, with optical path of 1 cm, I believe... — Preceding unsigned comment added by 200.16.16.13 (talk) 19:33, 26 September 2014 (UTC)[reply]

So, the conversion is as follows: E1%= 10g mol MW^-1 L ^-1 ε b

Or, the other way around:

ε=E1% MW L mol^-1 b^-1 g^-1 /10 — Preceding unsigned comment added by 200.16.16.13 (talk) 19:39, 26 September 2014 (UTC)[reply]

Request for clarification[edit]

What is it commonly known by and what is it actually known as, as the lead is somewhat ambiguous. Per WP:COMMONNAME, the article should be located at the article title it is most commonly known. WP:CHEMNAME covers elements and compounds and not other chemistry related articles, thus this article is not covered by that naming convention. —James ^{(Talk • Contribs)} • 6:48pm • 08:48, 8 November 2011 (UTC)[reply]

External links modified (February 2018)[edit]

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Swap article title to Extinction coefficient?[edit]

I have recorded or examined spectra for several decades, but I have never encountered the term "attenuation coefficient". Never even seen the term before just a few seconds ago in my attempt to learn about extinction coefficients for IR bands. I started a discussion on moving the title to something that practitioners actually use vs what IUPAC thinks we should use. See Wikipedia talk:WikiProject Chemistry#Molar attenuation coefficient.--Smokefoot (talk) 21:46, 28 November 2022 (UTC)[reply]

There is a pending proposal to move this to Molar absorption coefficient at the discussion linked above. Mdewman6 (talk) 20:21, 1 December 2022 (UTC)[reply]