Author Topic: Specifying Unanalyzed Elements For a Proper Matrix Correction  (Read 17002 times)

AndrewLocock

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Re: Specifying Unanalyzed Elements For a Proper Matrix Correction
« Reply #60 on: July 11, 2019, 02:19:08 pm »
Hello,
Although end-member tremolite has the formula: □Ca2(Mg5)(Si8)O22(OH)2, where □ indicates a vacancy on the A-site of amphibole, other amphiboles have substitutions for Si (and for hydroxyl).

Thus, end-member kaersutite has the formula: NaCa2(Mg3TiAl)(Si6Al2)O22O2.
Similarly, end-member pargasite has the formula: NaCa2(Mg4Al)(Si6Al2)O22(OH)2.

For the hydroxyl group of amphiboles, if Cl and F are assumed to be absent, one could specify 2 hydroxyl groups.
In both end-member tremolite and end-member pargasite, the ratio of H to O would therefore be 2 to 24, or 0.083333:1.

It is critical that the output in weight percent be expressed as neutral oxides, that is, H2O.

End-member ideal tremolite has the following oxide weight percent composition:
SiO2 59.17, MgO 24.81, CaO 13.81, H2O 2.22 wt%, sum 100.01 (all rounded to 2 decimal places).

End-member ideal pargasite has the following oxide weight percent composition:
SiO2 43.13, Al2O3 18.30, MgO 19.29, CaO 13.42, Na2O 3.71, H2O 2.16 wt%, sum 100.01 (all rounded to 2 decimal places).

Because Si varies considerably (in principle from 5 atoms per formula unit in sadanagaite to 8 in tremolite), it is not a good choice as a basis for H calculation. Oxygen should be better (assuming no oxo-substitution).

All the best,
Andrew



Probeman

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Re: Specifying Unanalyzed Elements For a Proper Matrix Correction
« Reply #61 on: July 11, 2019, 02:25:03 pm »
I'm completely confused now.  Some of that oxygen in the formula isn't associated with the cations.  If I just specify hydrogen elementally relative to the calculated oxygen, it won't add in the additional oxygen in hydroxl or water.  Correct? 

So what *exactly* would you do in the Calculation Options dialog?

« Last Edit: July 11, 2019, 02:28:40 pm by Probeman »
The only stupid question is the one not asked!

Probeman

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Re: Specifying Unanalyzed Elements For a Proper Matrix Correction
« Reply #62 on: July 11, 2019, 02:36:03 pm »
If I specify .08333 hydrogens to calculated oxygen I get:

Oxygen Calculated by Cation Stoichiometry and Included in the Matrix Correction
Element H is Calculated  .08333 Atoms Relative To 1.0 Atom of Oxygen


Using Conductive Coating Correction For Electron Absorption and X-Ray Transmission:
Sample Coating=C, Density=2.1 gm/cm3, Thickness=200 angstroms, Sin(Thickness)=311.145 angstroms

Un   13 AZ asbestos gr6, Results in Elemental Weight Percents
 
ELEM:       Na      Si       K      Al      Fe      Mg      Ca      Cl      Ti       F      Mn      Zn       O       H
TYPE:     ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    CALC    STOI
BGDS:      MAN     MAN     LIN     MAN     MAN     MAN     MAN     LIN     LIN     LIN     LIN     LIN
TIME:    40.00   40.00   20.00   40.00   40.00  165.00  150.00  120.00   30.00  120.00   30.00   30.00     ---     ---
BEAM:    29.92   29.92   29.92   29.92   29.92   29.92   29.92   29.92   29.92   29.92   29.92   29.92     ---     ---

ELEM:       Na      Si       K      Al      Fe      Mg      Ca      Cl      Ti       F      Mn      Zn       O       H   SUM 
   642   -.010  26.802    .093    .099   2.825  13.397   9.163    .004   -.026   -.065    .144    .022  47.925    .250 100.624
   643    .006  26.921    .071    .108   2.586  13.481   9.167    .000   -.019    .050    .168    .007  48.069    .250 100.866
   644    .008  26.967    .065    .097   2.687  13.505   9.162    .004   -.009   -.028    .138    .021  48.156    .250 101.025
   645    .047  26.935    .061    .087   2.477  13.540   9.253    .003    .007   -.073    .136    .023  48.138    .250 100.885
   646    .067  26.952    .066    .028   2.355  13.492   9.382   -.003   -.022   -.048    .107   -.033  48.059    .251 100.655

AVER:     .024  26.915    .071    .084   2.586  13.483   9.226    .002   -.014   -.033    .139    .008  48.070    .250 100.811
SDEV:     .032    .066    .013    .032    .182    .053    .096    .003    .013    .049    .021    .024    .091    .000    .169
SERR:     .014    .029    .006    .014    .081    .024    .043    .001    .006    .022    .010    .011    .041    .000
%RSD:   136.38     .24   18.19   38.02    7.03     .39    1.04  159.31  -97.92 -151.40   15.48  295.56     .19     .10
STDS:      336     162     374     336     162     162     162     285      22     835      25     660     ---     ---

STKF:    .0735   .2018   .1132   .1332   .0950   .0568   .1027   .0602   .5547   .1715   .7341   .4865     ---     ---
STCT:    58.60  246.04  197.64  255.36   19.35   72.74  178.88   61.41   44.86   13.54  136.63   66.08     ---     ---

UNKF:    .0001   .2126   .0006   .0006   .0215   .0926   .0838   .0000  -.0001  -.0001   .0011   .0001     ---     ---
UNCT:      .10  259.20    1.11    1.10    4.38  118.69  146.07     .01    -.01    -.01     .21     .01     ---     ---
UNBG:      .30     .20     .95     .80     .22     .52     .99     .37     .06     .05     .15     .36     ---     ---

ZCOR:   1.9014  1.2659  1.1175  1.4587  1.2014  1.4554  1.1004  1.2304  1.2048  4.1651  1.2217  1.2664     ---     ---
KRAW:    .0017  1.0535   .0056   .0043   .2265  1.6316   .8165   .0002  -.0002  -.0005   .0015   .0001     ---     ---
PKBG:     1.34 1319.20    2.18    2.37   20.95  228.69  149.12    1.04     .86     .90    2.43    1.03     ---     ---
INT%:     ----    ----    ----    ----    -.01    ----    ----    ----    ----   76.60    ----    ----     ---     ---

TDI%:    2.963    .033  -2.002  -3.947   -.711    .000    .000    .000    .000    .000    .000    .000     ---     ---
DEV%:       .2      .1    18.6    23.1     3.4      .0      .0      .0      .0      .0      .0      .0     ---     ---
TDIF:  HYP-EXP LOG-LIN LOG-LIN LOG-LIN LOG-LIN    ----    ----    ----    ----    ----    ----    ----     ---     ---
TDIT:   111.80  112.60   78.00  111.00  115.40     .00     .00     .00     .00     .00     .00     .00     ---     ---
TDII:     .369    259.    2.01    1.84    4.57    ----    ----    ----    ----    ----    ----    ----     ---     ---
TDIL:    -.996    5.56    .697    .611    1.52    ----    ----    ----    ----    ----    ----    ----     ---     ---

Un   13 AZ asbestos gr6, Results in Oxide Weight Percents

ELEM:     Na2O    SiO2     K2O   Al2O3     FeO     MgO     CaO      Cl    TiO2       F     MnO     ZnO       O      HO   SUM 
   642   -.014  57.339    .112    .187   3.634  22.216  12.821    .004   -.044   -.065    .186    .028    .000   4.219 100.624
   643    .009  57.593    .086    .204   3.327  22.356  12.827    .000   -.032    .050    .216    .009    .000   4.221 100.866
   644    .011  57.691    .078    .183   3.457  22.396  12.820    .004   -.015   -.028    .179    .026    .000   4.222 101.025
   645    .063  57.623    .073    .164   3.187  22.454  12.947    .003    .012   -.073    .176    .029    .000   4.226 100.885
   646    .091  57.660    .079    .054   3.030  22.373  13.128   -.003   -.036   -.048    .139   -.042    .000   4.229 100.655

AVER:     .032  57.581    .086    .158   3.327  22.359  12.909    .002   -.023   -.033    .179    .010    .000   4.223 100.811
SDEV:     .043    .140    .016    .060    .234    .088    .134    .003    .022    .049    .028    .030    .000    .004    .169
SERR:     .019    .063    .007    .027    .105    .039    .060    .001    .010    .022    .012    .013    .000    .002
%RSD:   136.38     .24   18.19   38.02    7.03     .39    1.04  159.31  -97.92 -151.40   15.48  295.56  418.33     .10
STDS:      336     162     374     336     162     162     162     285      22     835      25     660     ---     ---
The only stupid question is the one not asked!

AndrewLocock

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    • University of Alberta Electron Microprobe Laboratory
Re: Specifying Unanalyzed Elements For a Proper Matrix Correction
« Reply #63 on: July 11, 2019, 03:01:04 pm »
I'm completely confused now.  Some of that oxygen in the formula isn't associated with the cations.  If I just specify hydrogen elementally relative to the calculated oxygen, it won't add in the additional oxygen in hydroxl or water.  Correct? 

So what *exactly* would you do in the Calculation Options dialog?

Sorry to cause confusion.
The program actually does better than you might expect!

Let me explain with the example of apophyllite, ideal formula: KCa4Si8O20(OH)·8H2O
The ratio of hydrogen to oxygen in this formula is 17 to 29, or about 0.58621:1.
From the Handbook of Mineralogy entry for hydroxyapophyllite, the ideal oxide weight percents are:
SiO2 53.10, CaO 24.78, K2O 5.20, H2O 16.92 wt%, sum 100.00.

I ran some apophyllite analyses last year.
The measured oxides were: Na2O, SiO2, K2O, Al2O3, CaO, MgO, and BaO.
In the Calculation Options window, I selected:
Stoichiometry to Calculated Oxygen 0.58621 Atoms of H to 1 Oxygen
(This is shown in the attached MS-Word document entitled "apophyllite example.docx").

The results (also in the attached MS-Word document) are:
              Na2O   SiO2   K2O   Al2O3   CaO   MgO   BaO   H2O   Total
Average: 0.03   52.98   4.81   0.02   24.52   0.01  0.00   16.98   99.36

Thus, the program has calculated the presence of 16.98 wt% H2O.
If I calculate the formula proportions (on the basis of 8 Si+Al), I get:

Si7.998 Al0.002 Ca3.966 Na0.010 K0.926 H17.101, with 28.98 O by charge balance.
(Remember, the ideal is Si8, Ca4, K1, H17, O29).

I consider this to be pretty good initial results for a hydroxylated- and hydrated-mineral.

The take-home message is that Probe-for-EPMA can calculate the appropriate content of H2O.
Just try it!
(I have equally good results for analcime, NaAlSi2O6·H2O).

Best regards,
Andrew


AndrewLocock

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Re: Specifying Unanalyzed Elements For a Proper Matrix Correction
« Reply #64 on: July 11, 2019, 03:31:54 pm »
I should also note that the major element composition of that apophyllite without any calculated OH & H2O was:
SiO2 51.23, K2O 4.65 CaO 23.79, sum 79.67 wt%.

Thus, the calculated OH & H2O content made significant changes (about 3% relative) in these major elements during the data reduction process.
The major element results:
               SiO2   K2O    CaO    H2O   
Average: 52.98   4.81  24.52   16.98

Cheers,
Andrew

Probeman

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    • John Donovan
Re: Specifying Unanalyzed Elements For a Proper Matrix Correction
« Reply #65 on: July 11, 2019, 04:28:46 pm »
Sorry to cause confusion.
The program actually does better than you might expect!

Let me explain with the example of apophyllite, ideal formula: KCa4Si8O20(OH)·8H2O
The ratio of hydrogen to oxygen in this formula is 17 to 29, or about 0.58621:1.
From the Handbook of Mineralogy entry for hydroxyapophyllite, the ideal oxide weight percents are:
SiO2 53.10, CaO 24.78, K2O 5.20, H2O 16.92 wt%, sum 100.00.

I ran some apophyllite analyses last year.
The measured oxides were: Na2O, SiO2, K2O, Al2O3, CaO, MgO, and BaO.
In the Calculation Options window, I selected:
Stoichiometry to Calculated Oxygen 0.58621 Atoms of H to 1 Oxygen
(This is shown in the attached MS-Word document entitled "apophyllite example.docx").

The results (also in the attached MS-Word document) are:
              Na2O   SiO2   K2O   Al2O3   CaO   MgO   BaO   H2O   Total
Average: 0.03   52.98   4.81   0.02   24.52   0.01  0.00   16.98   99.36

Thus, the program has calculated the presence of 16.98 wt% H2O.
If I calculate the formula proportions (on the basis of 8 Si+Al), I get:

Si7.998 Al0.002 Ca3.966 Na0.010 K0.926 H17.101, with 28.98 O by charge balance.
(Remember, the ideal is Si8, Ca4, K1, H17, O29).

I consider this to be pretty good initial results for a hydroxylated- and hydrated-mineral.

The take-home message is that Probe-for-EPMA can calculate the appropriate content of H2O.
Just try it!
(I have equally good results for analcime, NaAlSi2O6·H2O).

Best regards,
Andrew

Hi Andrew,
OK, wow, that makes more sense.  So if I specify 0.08333 hydrogens to each oxygen (and specifying hydrogen oxide as H2O), I get this:

Oxygen Calculated by Cation Stoichiometry and Included in the Matrix Correction
Element H is Calculated  .08333 Atoms Relative To 1.0 Atom of Oxygen

Using Conductive Coating Correction For Electron Absorption and X-Ray Transmission:
Sample Coating=C, Density=2.1 gm/cm3, Thickness=200 angstroms, Sin(Thickness)=311.145 angstroms

Un   13 AZ asbestos gr6, Results in Elemental Weight Percents
 
ELEM:       Na      Si       K      Al      Fe      Mg      Ca      Cl      Ti       F      Mn      Zn       O       H
TYPE:     ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    CALC    STOI
BGDS:      MAN     MAN     LIN     MAN     MAN     MAN     MAN     LIN     LIN     LIN     LIN     LIN
TIME:    40.00   40.00   20.00   40.00   40.00  165.00  150.00  120.00   30.00  120.00   30.00   30.00     ---     ---
BEAM:    29.92   29.92   29.92   29.92   29.92   29.92   29.92   29.92   29.92   29.92   29.92   29.92     ---     ---

ELEM:       Na      Si       K      Al      Fe      Mg      Ca      Cl      Ti       F      Mn      Zn       O       H   SUM 
   642   -.011  26.791    .093    .099   2.822  13.344   9.163    .004   -.026   -.064    .144    .022  45.847    .244  98.472
   643    .006  26.909    .071    .108   2.583  13.427   9.167    .000   -.019    .050    .167    .007  45.989    .245  98.711
   644    .007  26.955    .065    .097   2.684  13.452   9.162    .004   -.009   -.028    .138    .021  46.076    .245  98.870
   645    .046  26.923    .061    .087   2.474  13.486   9.253    .003    .007   -.072    .136    .023  46.055    .245  98.728
   646    .066  26.940    .066    .028   2.353  13.437   9.382   -.003   -.022   -.048    .107   -.033  45.974    .245  98.494

AVER:     .023  26.904    .071    .084   2.583  13.429   9.225    .002   -.014   -.032    .139    .008  45.988    .245  98.655
SDEV:     .032    .065    .013    .032    .182    .053    .096    .003    .013    .049    .021    .024    .090    .000    .169
SERR:     .014    .029    .006    .014    .081    .024    .043    .001    .006    .022    .010    .011    .040    .000
%RSD:   140.42     .24   18.19   38.06    7.04     .39    1.04  159.31  -97.92 -151.40   15.48  295.57     .20     .10
STDS:      336     162     374     336     162     162     162     285      22     835      25     660     ---     ---

STKF:    .0735   .2018   .1132   .1332   .0950   .0568   .1027   .0602   .5547   .1715   .7341   .4865     ---     ---
STCT:    58.60  246.04  197.64  255.36   19.35   72.74  178.88   61.41   44.86   13.54  136.63   66.08     ---     ---

UNKF:    .0001   .2126   .0006   .0006   .0215   .0926   .0838   .0000  -.0001  -.0001   .0011   .0001     ---     ---
UNCT:      .10  259.20    1.11    1.10    4.38  118.68  146.06     .01    -.01    -.01     .21     .01     ---     ---
UNBG:      .30     .20     .95     .81     .22     .53     .99     .37     .06     .05     .15     .36     ---     ---

ZCOR:   1.8912  1.2654  1.1175  1.4576  1.2006  1.4496  1.1004  1.2318  1.2048  4.1235  1.2210  1.2653     ---     ---
KRAW:    .0016  1.0535   .0056   .0043   .2264  1.6315   .8165   .0002  -.0002  -.0005   .0015   .0001     ---     ---
PKBG:     1.32 1312.38    2.18    2.37   20.78  226.62  148.12    1.04     .86     .90    2.43    1.03     ---     ---
INT%:     ----    ----    ----    ----    -.01    ----    ----    ----    ----   76.60    ----    ----     ---     ---

TDI%:    2.963    .033  -2.002  -3.947   -.711    .000    .000    .000    .000    .000    .000    .000     ---     ---
DEV%:       .2      .1    18.6    23.1     3.4      .0      .0      .0      .0      .0      .0      .0     ---     ---
TDIF:  HYP-EXP LOG-LIN LOG-LIN LOG-LIN LOG-LIN    ----    ----    ----    ----    ----    ----    ----     ---     ---
TDIT:   111.80  112.60   78.00  111.00  115.40     .00     .00     .00     .00     .00     .00     .00     ---     ---
TDII:     .369    259.    2.01    1.84    4.57    ----    ----    ----    ----    ----    ----    ----     ---     ---
TDIL:    -.996    5.56    .697    .611    1.52    ----    ----    ----    ----    ----    ----    ----     ---     ---

Un   13 AZ asbestos gr6, Results in Oxide Weight Percents

ELEM:     Na2O    SiO2     K2O   Al2O3     FeO     MgO     CaO      Cl    TiO2       F     MnO     ZnO       O     H2O   SUM 
   642   -.015  57.315    .112    .186   3.631  22.128  12.821    .004   -.044   -.064    .186    .028    .000   2.184  98.472
   643    .008  57.568    .086    .204   3.323  22.266  12.826    .000   -.032    .050    .216    .009    .000   2.186  98.711
   644    .010  57.667    .078    .183   3.453  22.307  12.819    .004   -.015   -.028    .179    .026    .000   2.186  98.870
   645    .062  57.598    .073    .164   3.183  22.364  12.947    .003    .012   -.072    .176    .029    .000   2.188  98.728
   646    .089  57.634    .079    .053   3.027  22.283  13.127   -.003   -.036   -.048    .139   -.042    .000   2.190  98.494

AVER:     .031  57.556    .086    .158   3.323  22.270  12.908    .002   -.023   -.032    .179    .010    .000   2.187  98.655
SDEV:     .043    .140    .016    .060    .234    .087    .134    .003    .022    .049    .028    .030    .000    .002    .169
SERR:     .019    .063    .007    .027    .105    .039    .060    .001    .010    .022    .012    .013    .000    .001
%RSD:   140.42     .24   18.19   38.06    7.04     .39    1.04  159.31  -97.92 -151.40   15.48  295.57   69.72     .10
STDS:      336     162     374     336     162     162     162     285      22     835      25     660     ---     ---

And as you and Brian said, the total is a little low, probably out of focus. Looking at another sample I get this:

Oxygen Calculated by Cation Stoichiometry and Included in the Matrix Correction
Element H is Calculated  .08333 Atoms Relative To 1.0 Atom of Oxygen

Using Conductive Coating Correction For Electron Absorption and X-Ray Transmission:
Sample Coating=C, Density=2.1 gm/cm3, Thickness=200 angstroms, Sin(Thickness)=311.145 angstroms

Un    3 AZ asbestos gr1, Results in Elemental Weight Percents
 
ELEM:       Na      Si       K      Al      Fe      Mg      Ca      Cl      Ti       F      Mn      Zn       O       H
TYPE:     ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    CALC    STOI
BGDS:      MAN     MAN     LIN     MAN     MAN     MAN     MAN     LIN     LIN     LIN     LIN     LIN
TIME:    40.00   40.00   20.00   40.00   40.00  165.00  150.00  120.00   30.00  120.00   30.00   30.00     ---     ---
BEAM:    29.90   29.90   29.90   29.90   29.90   29.90   29.90   29.90   29.90   29.90   29.90   29.90     ---     ---

ELEM:       Na      Si       K      Al      Fe      Mg      Ca      Cl      Ti       F      Mn      Zn       O       H   SUM 
   138    .008  26.996    .051    .014   2.275  13.729   9.586    .004    .026   -.031    .082    .025  46.289    .245  99.298
   139    .008  27.285    .040    .033   2.379  13.658   9.453    .006    .008    .040    .133   -.028  46.554    .245  99.813
   140    .030  27.073    .065    .050   2.282  13.667   9.501    .002    .013   -.032    .080   -.048  46.323    .245  99.251
   141    .055  27.055    .032    .055   2.533  13.677   9.358    .000    .011    .009    .136   -.010  46.350    .245  99.505
   142    .037  27.221    .028    .016   2.592  13.659   9.399    .004    .014    .005    .107    .017  46.519    .245  99.861
   143    .059  27.190    .059    .042   2.310  13.713   9.476    .004   -.002    .004    .101    .037  46.501    .245  99.740
   144    .082  27.189    .043    .080   2.457  13.619   9.446   -.001   -.019   -.052    .028    .004  46.468    .245  99.589

AVER:     .040  27.144    .045    .041   2.404  13.674   9.460    .003    .007   -.008    .095    .000  46.429    .245  99.580
SDEV:     .027    .104    .014    .023    .126    .037    .073    .002    .014    .031    .037    .030    .106    .000    .242
SERR:     .010    .039    .005    .009    .048    .014    .028    .001    .005    .012    .014    .011    .040    .000
%RSD:    68.48     .38   30.26   56.41    5.25     .27     .78   93.90  205.40 -385.54   38.60-8861.00     .23     .08
STDS:      336     162     374     336     162     162     162     285      22     835      25     660     ---     ---

STKF:    .0735   .2018   .1132   .1332   .0950   .0568   .1027   .0602   .5547   .1715   .7341   .4865     ---     ---
STCT:    55.79  246.63  196.50  255.38   19.50   71.86  178.02   66.46   44.04   14.00  136.85   66.47     ---     ---

UNKF:    .0002   .2145   .0004   .0003   .0200   .0945   .0860   .0000   .0001   .0000   .0008   .0000     ---     ---
UNCT:      .16  262.18     .70     .55    4.11  119.57  149.02     .02     .00     .00     .15     .00     ---     ---
UNBG:      .30     .21     .96     .82     .22     .54    1.01     .36     .05     .05     .17     .38     ---     ---

ZCOR:   1.8837  1.2652  1.1173  1.4579  1.2011  1.4474  1.1006  1.2318  1.2033  4.1276  1.2215  1.2656     ---     ---
KRAW:    .0029  1.0631   .0036   .0021   .2106  1.6638   .8371   .0003   .0001  -.0001   .0011   .0000     ---     ---
PKBG:     1.53 1227.91    1.74    1.67   20.07  223.49  149.16    1.07    1.12     .98    1.91    1.00     ---     ---
INT%:     ----    ----    ----    ----    -.01    ----    ----    ----    ---- -129.12    ----    ----     ---     ---

TDI%:    7.889    .289  -4.914   1.125    .386    .000    .000    .000    .000    .000    .000    .000     ---     ---
DEV%:       .2      .1    29.7    56.7     3.6      .0      .0      .0      .0      .0      .0      .0     ---     ---
TDIF:  HYP-EXP LOG-LIN LOG-LIN LOG-LIN LOG-LIN    ----    ----    ----    ----    ----    ----    ----     ---     ---
TDIT:   116.14  116.14   81.43  114.71  120.57     .00     .00     .00     .00     .00     .00     .00     ---     ---
TDII:     .435    262.    1.58    1.33    4.32    ----    ----    ----    ----    ----    ----    ----     ---     ---
TDIL:    -.832    5.57    .460    .286    1.46    ----    ----    ----    ----    ----    ----    ----     ---     ---

Un    3 AZ asbestos gr1, Results in Oxide Weight Percents

ELEM:     Na2O    SiO2     K2O   Al2O3     FeO     MgO     CaO      Cl    TiO2       F     MnO     ZnO       O     H2O   SUM 
   138    .011  57.754    .061    .026   2.927  22.766  13.413    .004    .043   -.031    .106    .031    .000   2.187  99.298
   139    .011  58.372    .048    .062   3.061  22.648  13.227    .006    .013    .040    .172   -.035    .000   2.188  99.813
   140    .041  57.919    .078    .095   2.936  22.664  13.294    .002    .021   -.032    .103   -.060    .000   2.190  99.251
   141    .074  57.880    .039    .105   3.258  22.681  13.094    .000    .018    .009    .176   -.013    .000   2.185  99.505
   142    .049  58.235    .033    .030   3.335  22.651  13.151    .004    .023    .005    .139    .021    .000   2.185  99.861
   143    .079  58.170    .071    .079   2.971  22.741  13.259    .004   -.004    .004    .131    .046    .000   2.187  99.740
   144    .110  58.167    .052    .152   3.161  22.585  13.216   -.001   -.032   -.052    .037    .005    .000   2.189  99.589

AVER:     .054  58.071    .055    .078   3.093  22.676  13.236    .003    .012   -.008    .123    .000    .000   2.187  99.580
SDEV:     .037    .222    .017    .044    .162    .061    .103    .002    .024    .031    .048    .038    .000    .002    .242
SERR:     .014    .084    .006    .017    .061    .023    .039    .001    .009    .012    .018    .014    .000    .001
%RSD:    68.48     .38   30.26   56.41    5.25     .27     .78   93.90  205.40 -385.54   38.60-8860.99     .00     .08
STDS:      336     162     374     336     162     162     162     285      22     835      25     660     ---     ---

Which is much better. Dang, geology is complicated compared to physics!

Now I'm almost afraid to ask, but can you tell me why the tremolite formula is stated as Ca2(Mg5)(Si8)O22(OH)2 when Ca2(Mg5)(Si8)O23(H2O) is chemically the same? Which to me makes more sense considering how hydrogen (oxide) needs to be treated.
« Last Edit: July 11, 2019, 05:32:48 pm by Probeman »
The only stupid question is the one not asked!

AndrewLocock

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Re: Specifying Unanalyzed Elements For a Proper Matrix Correction
« Reply #66 on: July 12, 2019, 07:42:53 am »
Now I'm almost afraid to ask, but can you tell me why the tremolite formula is stated as Ca2(Mg5)(Si8)O22(OH)2 when Ca2(Mg5)(Si8)O23(H2O) is chemically the same? Which to me makes more sense considering how hydrogen (oxide) needs to be treated.

It has to do with how the hydrogen is present in the crystal structure.

In the case of hydroxyl, the hydrogen is located at about 0.9 to 1 angstrom away from an oxygen atom.

In the case of an H2O molecule ("water molecule"), two hydrogen atoms are located about 0.9 to 1 angstrom away from a single oxygen atom.

The H2O molecule is not linear, so in a crystal structure the central oxygen also tends to be attracted to a cation.
And, the hydrogen atoms of this H2O group may be weakly attracted to other oxygen atoms (usually within 2 to 3 angstroms distance) - this is the so-called "hydrogen bonding", for which the best example is ice.

Although it is possible to express a formula in different ways, e.g., Mg(OH)2 could be expressed as MgO·H2O, it is best to use the formula the reflects what is present in the crystal structure (or glass). In the example of apophyllite KCa4Si8O20(OH)·8H2O, both hydroxyl and H2O are present. And in tremolite, hydroxyl groups are present, but H2O groups are not.

Finally, in a chemical analysis that is expressed at neutral oxides, the hydrogen content should be expressed as H2O, regardless of how it is present in the crystal structure or glass.

Cheers,
Andrew
« Last Edit: July 12, 2019, 08:22:36 am by John Donovan »

Probeman

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    • John Donovan
Re: Specifying Unanalyzed Elements For a Proper Matrix Correction
« Reply #67 on: July 12, 2019, 08:26:20 am »
Now I'm almost afraid to ask, but can you tell me why the tremolite formula is stated as Ca2(Mg5)(Si8)O22(OH)2 when Ca2(Mg5)(Si8)O23(H2O) is chemically the same? Which to me makes more sense considering how hydrogen (oxide) needs to be treated.

It has to do with how the hydrogen is present in the crystal structure.

In the case of hydroxyl, the hydrogen is located at about 0.9 to 1 angstrom away from an oxygen atom.

In the case of an H2O molecule ("water molecule"), two hydrogen atoms are located about 0.9 to 1 angstrom away from a single oxygen atom.

The H2O molecule is not linear, so in a crystal structure the central oxygen also tends to be attracted to a cation.
And, the hydrogen atoms of this H2O group may be weakly attracted to other oxygen atoms (usually within 2 to 3 angstroms distance) - this is the so-called "hydrogen bonding", for which the best example is ice.

Although it is possible to express a formula in different ways, e.g., Mg(OH)2 could be expressed as MgO·H2O, it is best to use the formula the reflects what is present in the crystal structure (or glass). In the example of apophyllite KCa4Si8O20(OH)·8H2O, both hydroxyl and H2O are present. And in tremolite, hydroxyl groups are present, but H2O groups are not.

Finally, in a chemical analysis that is expressed at neutral oxides, the hydrogen content should be expressed as H2O, regardless of how it is present in the crystal structure or glass.

Cheers,
Andrew

Hi Andrew,
Thank-you. This sort of makes sense, even to a non-geologist like me!   ;D
The only stupid question is the one not asked!