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Dear Georges and Stan

thanks for your ideas, but I should have stated two things:

1) with "high precision" I think about numbers in the range of a permil, so
I aim to know my 0.1ml in the range of +-0.0001ml.
2) the "Gas Pipette" consists of two stainless steel all-metal valves
assembled with pneumatic heads, total weight in the order of several kg.

Therefore I have my doubt if the method of Stan using the exponential signal
decrease will work: It might be possible to determine the "large" volume
with +- 1 permil accuracy, but the volume partitioning needs exact knowledge
of the volume plus all connectors (including the bellow at the inlet side of
the pipette valve). Also I have my doubt if it is possible to determine the
slope in your formula with +- 0.1% precision. But I will try that and see
how it works out.

Concerning the mercury idea of Georges: weighting the mercury in the pipette
will surely not give the needed precision, since one will hardly find a
balance with a precision in the range of better than 1e-6 (determine the
total weight beeing around 3000g with +- 0.0013g corresponding to 0.0001ml
mercury). And I did not yet have a good idea to quantitatively get the
mercury into the pipette volume (and only into it, not around) and again
quantitatively out to determine the exact weight...

So again any idea for a high-vacuum tight, liquid nitrogen standing vessel
with less than 60g weight are appreciated.

Axel

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Axel Suckow
Isotope Hydrology Laboratory
International Atomic Energy Agency
Wagramer Strasse 5
A-1400 Vienna
Austria
Phone: 0043 1 2600 21767 or 26762
email: [log in to unmask] <mailto:[log in to unmask]>
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''


> -----Original Message-----
> From: Georges L. Paradis [mailto:[log in to unmask]]
> Sent: Donnerstag, 8. Juli 2004 20:18
> To: [log in to unmask]
> Subject: Re: gas-tight vessel
>
>
> Hi Axel,
>
> Hg can be used to accurately determine the volume since the
> density is well
> known.
>
> Take care,
> Georges
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Georges L. Paradis
> ICPMS Lab Manager
> Department of Geological Sciences / Marine Science Institute
> University of California Santa Barbara
> Santa Barbara, CA 93106
> (805) 893-7182
> [log in to unmask]
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ----- Original Message -----
> From: <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, July 08, 2004 4:41 AM
> Subject: [ISOGEOCHEM] gas-tight vessel
>
>
> > Hi everybody
> >
> > I need to determine the volume of a small (~0.1ml) gas
> pipette with high
> > precision.
> > My idea was to freeze some 100 gas fillings of CO2 or SF6
> at a defined
> > pressure via this pipette into a small volume and to determine the
> increase
> > in weight.
> > So: has anybody a good idea for a small gas-tight vessel that can be
> > evacuated to better that 1e-3Torr, that stands liquid
> nitrogen and that
> has
> > a weight of less than 60g (which is the maximum weight of
> our balance with
> > mg resolution)?
> >
> > Any hint welcome
> >
> > Axel
> >
> > '''''''''''''''''''''''''''''''''''''''''''''''''''''''''
> > Axel Suckow
> > Isotope Hydrology Laboratory
> > International Atomic Energy Agency
> > Wagramer Strasse 5
> > A-1400 Vienna
> > Austria
> > Phone: 0043 1 2600 21767 or 26762
> > email: [log in to unmask] <mailto:[log in to unmask]>
> > '''''''''''''''''''''''''''''''''''''''''''''''''''''''''
> >
> >
> > This email message is intended only for the use of the
> named recipient.
> > Information contained in this email message and its
> attachments may be
> > privileged, confidential and protected from disclosure. If
> you are not the
> > intended recipient, please do not read, copy, use or disclose this
> > communication to others. Also please notify the sender by
> replying to this
> > message and then delete it from your system.
> >
>


This email message is intended only for the use of the named recipient.
Information contained in this email message and its attachments may be
privileged, confidential and protected from disclosure. If you are not the
intended recipient, please do not read, copy, use or disclose this
communication to others. Also please notify the sender by replying to this
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