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NMP color

NMP color

NMP color

(OP)
Sorry for this stuip question. NMP is used as solvent. It is noted that the original color is brown or dark brown. Then it turns to yellow or light yellow. As I know it should be colorless or light yellow. Why does the color change so fast? By the way, we saved NMP in the glass bottle.

RE: NMP color

I believe NMP is clear to light yellow.  It oxidizes to brownish colors.  

I talked to a QC engineer at one of the manufacturers, and he said the reaction is very strange.  One of the products is NMS, but the coloring is very low concentration and proceeds less in air than in N2. (don't ask me why)

If it was brown and turned yellow, I don't know if this is applicable.  Did a precipitate form that was brown? or was the bottle open so a volatile could evolve?

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