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Stable Isotope Geochemistry

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Subject:
From:
Stephanie Ewing <[log in to unmask]>
Reply To:
Stable Isotope Geochemistry <[log in to unmask]>
Date:
Wed, 6 Jul 2005 14:40:53 -0700
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text/plain
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The HCl will be hard on your freeze dryer unless
you have an effective trap.  There's been lots of
discussion of various alternate acids on this
list.  I've used 100% phosphoric, which has the
benefit of low vapor pressure, but makes
subsequent dehydration challenging.

Stephanie

>Folks,
>
>We're trying to separate siderite from soil/clay samples so that we may
>analyze the organic components of the soil for d13C, d15N and CN ratios.
>The refs I've come across focus on 'carbonate' removal and indicate that
>siderite is less soluble. I found I can dissolve siderite in 6 molar HCl at
>50C overnite, or soaking in 6 molar HCl at 25C for several days. To
>remove excess HCl I plan to freeze dry the samples and not pour out any of
>the acid in case some of the organics have also gone into solution (I think
>this is the same idea as vapour removal).
>
>Any comments or suggestions regarding possible effects others have observed
>using this method, or better methods before I follow the tedious path of
>sample preparation testing? The first line of testing I was going to do was
>to dose IAEA-C5 (wood) with siderite and see if THIS pretreatment affected
>its d13C values.
>
>Thanks in advance for saving me time,
>
>Toti.
>
>
>Toti Larson Ph.D.
>Los Alamos National Laboratory
>Earth and Environmental Sciences                505.667.9894 (lab)
>Los Alamos, New Mexico 87545            550.667.8006 (office)


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