In a test tube, a few drops of phenolphthalein are added to 0.5 mL of a 1% solution of borax. A pink solution is formed. A couple of drops or a few crystals of the unknown are added. If the pink color begins to fade after the unknown and the reagent have been mixed together, then continue to add small amounts of the unknown until the pink color fades completely. Place the test tube in a hot water bath. If the pink color reappears on warming, and dissipates again on cooling, then the unknown is a polyhydric alcohol.
Carbohydrates and 1,2-diols give a positive test.
None.
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