Regarding the question about stability of the Conflo II with and without
venting, the following measurements were provided by Haiping Qi.

Using 24 cycles of standard on and standard off for CO2 gas:

d13C std dev with fan on and holes in side panels open = 0.06 per mill
d13C std dev with fan on and holes in side panels plugged = 0.05 per mill
d13C std dev with fan off and holes in side panels plugged = 0.06 per mill

Using 24 cycles of standard on and standard off for N2 gas:

d15N std dev with fan on and holes in side panels open = 0.08 per mill
d15N std dev with fan on and holes in side panels plugged = 0.12 per mill
d15N std dev with fan off and holes in side panels plugged = 0.08 per mill

The conclusion is that statistically there is no difference in stability
with the fan on or off or with or without holes in the side panels.




                    "Coleman,
                    Dennis D."             To:     [log in to unmask]
                    <coleman@ISOTEC        cc:
                    HLABS.COM>             Subject:     Re: Suggestions for using CO and a Safety Concern
                    Sent by: Stable        with the Conflo              II
                    Isotope
                    Geochemistry
                    <ISOGEOCHEM@LIS
                    T.UVM.EDU>


                    07/26/2001
                    03:06 PM
                    Please respond
                    to Stable
                    Isotope
                    Geochemistry





When we originally set up our Conflo II for hydrogen we too connected the
little exhaust fan that Finnigan supplied directly to a vent line.  But, we
discovered that the slightly negative pressure and/or the turbulence
created
inside the Conflo box caused instability in our reference peak (and
presumably also with the sample peak).  We assumed that this was resulting
from changes in the open split.  Providing vents at the bottom of the box
did not seem to decrease the problem.  We therefore chose to keep the box
sealed and to install a small exhaust blower in the ceiling which has a
hose
(like vacuum cleaner hose) that extends down over the vent tube on top of
the Conflo box. The end of the hose is larger than the vent so there is
always air flow up around the vent, but no negative pressure or turbulence
is created in the box.  This solved the instability problem.

We are only now starting to work with CO and some of your comments are
making me rethink this arrangement.  Obviously leakage of a small amount of
hydrogen was not a problem, but a small amount of CO would be.

I am wondering if Ty or Bill encountered any instability problems with the
venting methods they have used?

Dennis Coleman
Isotech Laboratories, Inc.