Why does the sample turn yellow after being washed with cadmium sulfate for catalytic gasoline?
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Recently, while working with thiol sulfides, I encountered hydrogen sulfide present in the catalytic gasoline. In accordance with national standards, cadmium sulfate was used to remove this hydrogen sulfide, but the sample turned yellow after coming into contact with cadmium sulfate, and this yellowing could not be removed even by further treatment with cadmium sulfate. Why is this?
Cadmium sulfide is yellow in color, so the appearance of yellow in the sample is a normal phenomenon. How is it possible to clean an insoluble cadmium sulfide using cadmium sulfate? Apart from the need for a certain period of time for settling to remove cadmium sulfide, these precipitates sink deep into the aqueous phase, allowing for separation. Why not look up information on this experimental phenomenon or ask other experienced workers around?
Adding cadmium sulfide is mainly to remove hydrogen sulfide; I didn’t say it’s to remove cadmium sulfide. This yellow color does not change much when left undisturbed; when forming thiol sulfides, should I consider this yellow color as a yellow precipitate? How can one determine that hydrogen sulfide has been completely removed?