Glen/others interested:
        We've done equilibration experiments for large samples (1.5cc; Socki
et al. Anal. Chem. 1992. vol 64, 7, p. 829) and small samples (10ul; Socki
et al. Anal. Chem. 1999, vol 71, 11, p. 2250).  Oxygen isotope exchange is
complete in no less than 1.5 hrs. for large samples (shaking) and 28 hrs.
(no shaking) for the small samples.
        I still have some reprints of these papers left.  To minimize
Andrea's headaches please send reprint requests to me and not the list
server!

Cheers,
Rick Socki
Sr. Geochemist
Stable Isotope Facilities
NASA/Lockheed
2400 NASA Rd.
Houston, TX 77058
(281) 483-9932 office
(281) 483-5317 lab
[log in to unmask]

> ----------
> From:         Dr. Dachun Zhang
> Reply To:     Stable Isotope Geochemistry
> Sent:         Friday, July 27, 2001 7:04 PM
> To:   [log in to unmask]
> Subject:      Re: CO2 equilibration
>
> Hi, Glen:
>
> Is it enough for one overnight equilibration between water and CO2?  One
> article says it takes five days. We use three days.
>
> Regards.
>
> Dachun Zhang
> Isotope Lab
> Zymax
>
>
> "Glen E. Martin" wrote:
>
> > Adam Porowski,
> >
> > We place  1 mL of sample water in a vacuum flask. Freeze the water, and
> > evacuate the air.
> > The water is melted, and the vacuum reaction flask (internal volume
> > 10-20mL) is filled with CO2(g) to ambient (atmospheric pressure) minus 5
> or
> > 10 cms Hg (using a mercury manometer).The sealed sample is equilibrated
> at
> > 25.3 degrees C overnight.
> >
> > The CO2(g) is extracted/purified the next day for analysis.
> >
> > G. Martin
> >
> >                     Adam Porowski
> >                     <[log in to unmask]        To:
> [log in to unmask]
> >                     AN.PL>                 cc:
> >                     Sent by: Stable        Subject:
> >                     Isotope
> >                     Geochemistry
> >                     <ISOGEOCHEM@LIS
> >                     T.UVM.EDU>
> >
> >                     07/27/01 03:04
> >                     AM
> >                     Please respond
> >                     to Stable
> >                     Isotope
> >                     Geochemistry
> >
> > Dear Isogeochem subscribers,
> >
> > I start to determine composition of stable isotope of oxygen (O18/O16)
> in
> > groundwaters. I am going to use equilibration with CO2 method. Actually,
> my
> > problem is how to bring up into the equilibration vessel proper, small
> > amount of CO2 gas from the tank (I have rather bad - rude - pressure
> > reducer in the tank). It means that I must do that on preparation line.
> > Could you please advise me how do you do that action? Does the amount of
> > CO2 for equilibration must be exactly the same each time (of course not
> > bigger than the calculated max amount depending on volume of water taken
> to
> > equilibration) or may be different?
> >
> > Thank you very much in advance.
> > Best regards for all!
> > #############################
> > Adam Porowski
> > Department of Hydrogeology
> > Institute of Geological Sciences
> > Polish Academy of Sciences
> > ul. Twarda 51/55
> > 00-818 Warsaw, POLAND
> > [log in to unmask]
> > tel: +48 22 697-87-56
> > fax: +48 22 620-62-23
>
>