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When you are at work or in public places want to drink water, how to
identify cups, which is used, which is not used, to make themselves more secure to use.Add a small amount of colorless and tasteless non-toxic substances in the production of paper cup bottom, when the water into the cup , use the chemical reaction, material to react with water, bottom color changed, so as to distinguish whether the unused cups.Let us more safe to drink water.
Yue / Zhang