Dear all,
        please avoid sending attachments to the whole list (1500
people....) irregardless of their size.
Use the file repository or send the files only to the interested parties.
Thanks!

Andrea Lini
(listowner)

>Dear Colleagues,
>
>I don t know whether I should continue on this matter or not. It
>looks that there are
>some who are interest in knowing it. In my opinion, too, the
>Isogeochem Server is a
>good opportunity to discuss our viewpoints and improve our
>understanding with the
>comments of others. Let me write first that I am a regular reader of
>GCA and it
>publishes excellent material. Of course, it is well established. My
>comments were only
>that the reviewers should put more attention when a mistake had been
>pointed out.
>People at least I use the information published there as granted.
>
>I worked out the problem using the activity approach. The data are
>given in the
>attached file. I use  Error and Trail method  to solve a non-linear
>equation. I do it
>in excel without writing any programming code. I don t think that anyone is
>interested in that. The basis mistake in the reply by Halas et al.
>(GCA, 64, 575-576,
>2000) was that their equation 5 should be K3=a(H)a(OH)/a(H2O). The
>values are given
>for their system (10 g Na2CO3+CO2 from 1g of Na2CO3). Again, there
>could be small
>differences if you use different constants. I tried to use the same
>constants as were
>given by Halas et al. I did the calculation without re-check. So,
>there could be some mistakes. I think it could be better if Halas et
>al. change
>equation 5 and re-calculate the parameters.
>
>Recently, we have started a project to study rainwater acidity
>around geothermal
>systems. We observed that it was really difficult to measure pH of
>pure water like
>rainwater with a pH-meter (rainwater characterization is based on pH
>around the world).
>Similarly there are problems in measuring pH of highly
>acidic or alkaline (more in case of alkaline) waters. (we are
>working to understand this).
>Additionally, the IAEA has
>conducted three interlab calibrations (Giggenbach, IAEA-TECDOC-641, Vienna,
>p.439-456, 1989 and two are very recent). If you look these reports,
>you will find
>that there is some improvement in the analysis after 10 years; but
>the quality of analysis
>of
>especially SiO2, HCO3 and CO3 is far bellow the expectations. That
>is different topic
>how to improve it. But the results indicate that in my viewpoint one
>should not
>design a fundamental experiment (like in discussion) where there is need of
>correcting isotopic measurements with chemical analysis. As I tried
>to explain it in
>my comments. The calculated  ratio of HCO3:CO3 is 18:82. So there is
>need of correcting the
>HCO3 contribution. One can calculate the propogation of error in
>their isotopic data due to
>the error in the chemical analysis.
>
>Secondly, the partial pressure of CO2 in vapor phase is very low
>(much less than
>10^-4 bars). If you are extracting 10 micromoles, you can calculate
>how much volume
>should be of the experimental vessel and how the vapor phase CO2 can
>be extracted
>only without changing its isotopic composition. The amount of water
>vapor will be
>much higher than that of CO2. Check the steam tables. When you
>condense this vapor
>some part of CO2 will get dissolved in the water. So there will be
>some fractionation
>in this process, too. So, there are many points one has to consider
>for this work. I
>do agree that some thing is better than nothing. This way the
>calculated values (with
>spectroscopic data) could be more accurate than the experimentally
>measured.  The
>measurement of isotopic
>fractionation for CO2(g) and carbonate is a challenging subject.
>Definitely, it is
>hard job to work on this type of problems. So, we should do
>encourage the people who are
>working such types of problems. My comments are just some suggestions,
>which may be considered during their work.
>
>Best regards
>
>Mahendra
>
>
>
>Attachment converted: GigaBook:calFnl.xls (XLS4/XCEL) (00036526)