In the Reinsch test, which color indicates mercury?

• A. silver gray
• B. dull black
• C. blue-black
• D. green

Answer: (A)

In the Reinsch test, mercury ions are reduced to metallic mercury and plated onto a copper strip, giving a distinctive silver-gray metallic coating. This silvery-gray sheen on the copper surface is the telltale sign of mercury presence. Other colors would not be characteristic of mercury deposition in this test, and the silver-gray coating helps distinguish mercury from other metals or substances.