Dear Peter

I got a similar problem with the NA 1500 some years ago. The memrane in the
6-port-valve, witch switches the O2 into the Helium flow, broke. So there
was a permanent O2-He-flow through the reduction tube. The tube got very
hot because of the exothermic reaction and the copper oxide melt totaly.

Hope this helps

Franz Buegger
Institute for Soil Ecology
GSF - National Research Center for Environment and Health
Ingolstaedter Landstr. 1
D-85764 Neuherberg/Germany

Tel.: +49-89-3187-3403
Fax:  +49-89-3187-3376
Email: [log in to unmask]



Peter Ditchfield schrieb:

> Dear Listmembers
> We have had a recent spate of Cu reduction tubes becoming blocked by
> some reaction taking place within the copper oxide which is forming as
> the copper becomes oxidised. The system is a Carlo Erba EA attached to
> a Europa geo 20/20 running in continuous flow mode. the reduction
> furnace runs at 600 C.
> Instead of the usual granular copper oxide replacing the granular
> copper we get a black shiny (viterfied) plug of solid copper oxide
> which blocks the He flow  and in bad cases fractures the silica tubing
> of the reduction column.
> There seems to be little pattern as to when it happens and is just as
> likely towards the end of the life of a reduction column as a few hours
> after a column change. The vast majority of samples that we process are
> collagen.
> Has anyone else had similar experiences? any thoughts on possible
> causes such as excess water in the combustion products?
>
> Dr. Peter Ditchfield
> Stable Isotope Laboratory Manager
> Research Laboratory for Archaeology
> University of Oxford
> 6 Keble Road, Oxford, OX1 3QJ, UK
> tel:01865-283647
> fax:01865-273932