Don't forget to add the eye of newt. :-). If anyone can tell me how adding
a few milliliters of hydrogen peroxide to a liter of phosphoric acid at 225
deg C does anything at all to the bulk of the acid, I will be happy to hear
it. The hydrogen peroxide is instantly vaporized on the surface on the
surface of the acid.
But then where would those of us in the stable isotope business be without
our arcane rituals.

As for the Chromium Trioxide. Its value seems to be as an an oxidation
state indicator, as well as a colorful marker to distinguish 100%
phosphoric from lab grade ortho phosphoric (85%).

Cheers to all,
Bob
====================
Stephen S. Howe wrote:

>Bjorn:

Snip, Sniip.....
>
>As to why it is added to the acid, I must confess I'm not entirely sure,
>especially as McCrea (1950) didn't add it to his phosphoric acid, as far as
>I can tell.  Old phosphoric acid turns a brownish color and I always
>thought the chromium was added to facilitate determining when it was time
>to make a new batch of acid.  Likewise, I assumed the addition of a few
>milliliters of hydrogen peroxide was to oxidize any organic matter in the
>acid, but maybe this too is folklore.
>
>Steve
>------------------

Bjcrn Buchardt wrote:

>>Dear isogeochemists
>>Since the dawn of stable isotope geochemistry it has been good
>>behaviour to spike the phosphoric acid for carbonate reactions with
>>CrO3. Now my technician tells me that this colourfull compound is
>>carcenogeneous and she wants (understandably) to avoid it.
>>Does anybody know why we add it and what would happen if we leave it
>>out?
>>Do anybody add it at all or is it just us being old fashioned?
>>Replies will be appreciated
>>Bjorn
>>
>



-----------------------------------------------------
Bob Fifer
Brown University                E-mail: [log in to unmask]
Providence, RI 02912            Geological Sciences

Phone:  401-863-1698
Fax:    401-863-2058