Paul:

I use quartz tube inserts and find that occasionally they stick a bit. This
happens mostly when the thicker-walled quartz reaction tubes (pre-made ones)
are used. When I prepare my own reaction tubes, I buy the slightly
thinner-walled quartz for the reaction tube and usually have no sticking
problems. I too put a small quartz wool plug at the bottom of the ash tube
and, of course, there is quartz wool at the top of the reactor tube. This
prevents most problems.

But in case of sticking, I have a thick piece of steel wire with a short
bend at the end. Wire must be thin enough to fit through the slits but thick
enough not to soften too quickly in the oven. I use this to move down inside
the tube and hook into one of the slits. I can usually pull them out this
way. Very simple and takes seconds to remove and replace. The only caveat is
that you have to make sure the wire doesn't sit in there too long or it
starts to soften. But even then you can just pull it back out, cool, rebend,
try again. I've never had one that I couldn't get out. I also follow Lola's
protocol and change after each run. When running sulfur as I often do, this
is critical and so it's just routine for me. And I also clean then out and
try to reuse them if I can. The wire is handy for that too.

--Alison

________________________________

Alison Pye  .  [log in to unmask] 
Stable Isotope Lab Coordinator
CREAIT . TERRA Facility . Stable Isotope Lab
Alexander Murray Building
Memorial University of Newfoundland
St. John's, NL . Canada . A1B 3X5
ph: (709) 737-3217 . fax: (709) 737-2589
 
-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
Of Paul Eby
Sent: February 26, 2009 3:33 PM
To: Alison Pye
Subject: ash tubes

Listmembers,

I've been having trouble with ash tubes from our EA breaking lately.

We use Elemental Microanalysis C1090, which is open both ends and has 
slits on the bottom half. I have a small bit of quartz wool at the 
bottom of the tube, and at the top of the reactor. Typically, the 
tube is stuck when I try to remove it, and breaks near the top of the 
ash level when I force it. This occurs regardless of whether I am at 
full temperature or standby temperature, and I have had the same 
trouble with tubes that are closed at the bottom.

My best guess is that the slag is seeping through the slits and 
fusing to the reactor tube. Does anyone have any applicable wisdom?

I'm considering the vacuum removal method at this point....

Paul Eby
University of Victoria