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Published on Jan 16, 2011
When three clear solutions are combined together, the mixture remains colorless for a few seconds, then it develops a bright orange precipitate and finally, after several more seconds, it suddenly turns black. Due to the colors which appear (orange and black), this demonstration is often called the "halloween clock reaction" or the "Old Nassau reaction" (the latter name refers to the Princeton University, where the reaction was discovered). Moreover, the timing between the transitions can be tuned by diluting the mixture with more water.