Sulfur Determination via Schoniger Combustion
The solid sample is weighed into ashless paper and inserted into custom made Platinum stopper. The stopper is fitted it a flask that is charged with the appropriate reactants and oxygen. On combustion the sulfur present is oxidized from SO2 to SO3. The resulting liquid is then removed and titrated. With an indicator the color change is gold ‡ pink. In cases with high levels of fluorine, it is best to add Boric acid.
The most common standard for this determination is Cystine available through the NIST. There are others that may be used on occasion.
The preceding is a brief description of our techniques used in sulfur determination. Due to the exclusive use of the flask combustion in the sulfur determination, we are not able to determine sulfur on air-sensitive samples.
Experience has shown that phosphorus does show some interference yielding lower results. This may depend on the structure and if there is a P-S bond.