Hullo Joy,


Considering what a hit and miss affair (literally) dropping silver capsules 
into a crucible can be (in our hands), I sometimes wonder why I bother. I 
should mention I am running samples on a high temperature glassy carbon 
system.

When they work, i.e. sitting snugly in the reactor tube so the capsule drop 
right in, we can run samples until the cows come home and have a nice 
silver rod sticking out of the crucible when we refurbish the reactor.

Sad reality is, the capsules miss the crucible more often than not (due to 
that part of sod's law where manufacturing specs for the reactor tube and 
the crucible conspire against you) and molten silver sinks through the 
reactor filling eventually reducing the net carrier flow.

This leads to peak broadening and poor results. Remedial action in form of 
a modified helium inlet connector have been discussed on the list (this 
will help keeping the carrier flow up for longer).

In short, when it works you get a clear benefit from the crucible in terms 
of high productivity (read high sample trough-put between reactor changes). 
When it doesn't work and you don't have a modified carrier gas inlet, 
silver build-up forces a reactor clean up every 100 samples or so (give or 
take 25).

I'm working on an alternative but it's early days. So, mum's the word.


Cheers,

Wolfram


On Sep 30 2005, Joy Davis wrote:

> Hello all,
> 
> We are not currently using crucibles in our oxygen pyrolysis system but 
> would like to consider the options. What are the pros and cons? What are 
> the factors in choosing them? Who is the preferred vendor?
>  
> All information is appreciated.  Thanks.
> 
> Joy Davis
> Old Dominion University
> Norfolk VA
>