Uses
Oil Red O is one of the dyes used for Sudan staining. Similar dyes include Sudan III, Sudan IV, and Sudan Black B. The staining has to be performed on fresh samples, as alcohol fixation removes the lipids.
Oil Red O largely replaced Sudan III and Sudan IV, as it provides much deeper red color and the stains are therefore much easier to see.
In pyrotechnics, Oil Red O is used in some compositions of red colored smokes. It is also used to dye some plastics, e.g. polystyrene resins.
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