Millon's reagent

noun

Mil·​lon's reagent mē-ˈlōnz- 

variants or Millon reagent

mē-ˈlōn- 

: a solution that is usually made by dissolving mercury in concentrated nitric acid and diluting with water and that when heated with phenolic compounds gives a red coloration used as a test especially for tyrosine and proteins containing tyrosine