Hi,

we are having problems measuring the delta 34S of our sulfate samples. After
heating the sample to 950 C, some white precipitates form in the glass tube.
This causes problems getting the necessary vacuum and the measurements are
unstable.

We assume that our sample is responsible for that problem (sulfides work
just fine). We precipitated the barium sulfate from the original water using
BaCl2. The barium sulfate was heated to a temperature of 650 C, cooled and
prepared for the measurement (mixed with V2O5).
The original water is a  highly mineralized pore water from material
influenced by sulfide oxidation (pH=2.3, el. conductivity = 3 mS/cm, sulfate
concentration 1 to 5 g/l, 50 to 800 mg/l).

Does anybody have had similar problems or any idea what the precipitate
might be?

I appreciate any suggestions.

Manuela