Under normal lighting conditions, this separatory funnel looked totally black. But when Lynn Stevens put it under an ultraviolet lamp, these distinct yellow and black phases revealed themselves. Stevens, an undergraduate at St. Mary’s College of Maryland, ran a reaction to make a fluorescent-yellow boron difluoride dye and was using the funnel to separate the product from unreacted starting material and other impurities. The dye dissolved into the organic dichloromethane phase, making it glow strongly yellow, while the less fluorescent impurities moved into the aqueous phase. Unfortunately, the separation got stuck in this jumbled emulsion. Stevens eventually broke the emulsion into two clean, separable layers by adding some sodium chloride to the mixture.
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