I was about to say the same. Bad idea.

The HCl will cause damage to your freeze dryer, and particularly the vacuum
pump (unless you put at least 2 liquid N2 traps in the line). As you know,
HCl itself is a gas (bp -85 C at 1013 mbar) and concentrated (or fuming) HCl
is a 38% solution of HCl in water. Your 6 molar HCl is roughly 2/3 of that.

Under vacuum, virtually the first thing to be pumped off will be gaseous
HCl.


Wolfram


> -----Original Message-----
> From: Stable Isotope Geochemistry
> [mailto:[log in to unmask]] On Behalf Of Stephanie Ewing
> Sent: 06 July 2005 22:41
> To: [log in to unmask]
> Subject: Re: siderite removal from clay/organics for d13C
>
>
> 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 50°C overnite, or soaking in 6 molar HCl
> at 25°C 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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