In case any one is interested, I wrote up a short note on why one should not specify unanalyzed elements, in Excel or other apps which do not calculate the change in the matrix physics. Particularly if these unanalyzed elements are present at major element weight percent levels:

https://probesoftware.com/smf/index.php?topic=92.msg7697#msg7697

This matrix effect of unanalyzed elements can be significant even in cases where the unanalyzed elements are only a few percent of the total, for example water by difference calculations in alkali glasses. 

It does depend somewhat on the specific emitters and compositions involved, but the magnitude of the effect on the analyzed elements surprised me when I first noticed it.  In the case of water by difference, it turns out that Si Ka is more heavily absorbed by water (oxygen) than by Si, so adding water to the matrix correction increases the Si concentration, which in turn decreases the water by difference calculation. Which is why the water by difference calculation needs to be in the matrix correction iteration loop.

john


On 10/12/2018 9:53 AM, John Donovan wrote:
[log in to unmask]">

All,

I know nothing about the JEOL software and haven't looked at Julien's script, but technically one should include the calculated CO2 in the matrix correction, because adding these unanalyzed elements does change the matrix correction physics, often significantly.

I think I'll write up a short post on this issue on the Probe Software User Forum.

john


On 10/12/2018 4:11 AM, Allaz Julien wrote:
[log in to unmask]"> Hi Tod,

I personally do not use the JEOL software for calculating the CO2 content. During the analysis, I simply specify a fixed amount (44% for calcite, 52% for magnesite, 38% for Fe-rich one, or an intermediate value), and recalculate the CO2 content offline using my little web-based script or an XL spreadsheet.

My own online tool is available here, you can simply copy & paste data from excel (without the column “total”): http://ethz.geoloweb.ch/index.php?page=mineral_formula&reset=true

Cheers,

Julien


On 12 Oct 2018, at 13:01, Tod Earle Waight <[log in to unmask]> wrote:

Hi all
I am running carbonates and having issues wrapping my head around the JEOL software.
I have set up the analyses as oxides, with CO2 added. In the element condition option under CAL I have the option to define how many CO2 are added for a group of specified elements and I have set up so (as I understand things) it should add 1 CO2 for 1 Ca, 1 Mg and 1 Fe. However, the software only adds CO2 for the first element on the list –  So I can run a calcite and it works perfectly, but if I run a dolomite it adds CO2 for Ca but not Mg.
Is this a software is or am I just doing something dumb!
Cheers
Tod
PS I am running a JEOL8200, with software from 2011 (VO1.55)
 
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John J. Donovan         [log in to unmask]
University of Oregon    (541) 346-4632 (office)
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Eugene, OR              (541) 346-6854 (FAX)
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