Dave Mattey wrote:

> Dear all
>
> We have been running D/H for the first time in several years using a 5 year
> old  batch of Indiana zinc that has been stored in an evacuated flask.   H
> conversion yields seem fine but D/H ratios correlate with sample size (20
> permil shift from 0.5 to 5 microlitres). All the obvious remedies have now
> been tried and I am forced into suspecting the zinc. Does anyone had a
> similar experienc using old zinc?  Can/should it be pretreated/regenerated
> in any way after languishing for so long?
>
> Thanks and best wishes
>
> Dave
>
> Dave Mattey
>
> Geology Dept, Royal Holloway College, University of London, Egham Hill,
> Egham, Surrey, TW20 0EX
>
> Tel:      01784  443587          Office
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I have always used calibrated capillaries and weighed the zinc to keep a
constant volume and amount of zinc per ampoule.  Otherwise the variability is
too large, even for a new batch of zinc.  Leo.