Kristine,

Dissolved sulphate can be easily precipitated 
from water without interference from carbonate by 
addition of 5% BaCl2 to previously acidified 
water. A pH as low as 2 is easily reached with 
minimum addition of, for example, HCl, that will 
not interfere with the species of interest.

You can still recover your original samples by 
acidification and washing. BaSO4 will not be 
affected by most acids, buth the carbonate will 
happily disappear!

Clemente



>Under what conditions does BaCO3 precipitate?  I 
>ask because a while ago I tried precipitating 
>BaSO4 from gulf of mexico porewaters and had a 
>coprecipitate with carbon in it (at least, 
>that's what the EA told me), but everyone I 
>asked claimed BaCO3 shouldn't precipitate at 
>all.  I'm rather relieved to know the compound 
>at least exists, and would be grateful for any 
>information on how and where it forms.
>
>Thanks,
>
>Kristine


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*******************************************
Dr. Clemente Recio
Laboratorio de Isótopos Estables
Fac. de Ciencias
Univ. de Salamanca
Plaza de la Merced, S/N
E-37008 SALAMANCA
               SPAIN

Phone: (+34) 923 29 45 00, Ext. 1540 (Automatic Switchboard)
Fax:     (+34) 923 29 45 14
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Web page: http://www.usal.es/isotopos
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