human
Millon's reagent, a solution of mercuric nitrate containing nitrous fumes. On warming the proteid with this reagent, a curdy pink precipitate or a red colour is obtained. This reaction is caused by the tyrosine group (p. oxy [alpha] amido phenyl-propionic acid). Another general reaction is to boil the protein with 1:2 nitric acid for some days. A yellow flocculent precipitate of