How to detect a protein

A few drops of the secret ingredient – and the egg white turns purple!

Safe­ty pre­cau­tions

At­ten­tion! All ex­per­i­ments are per­formed by pro­fes­sion­als. Do not at­tempt!


  • beaker;
  • chick­en eggs;
  • cop­per(II) sul­fate so­lu­tion;
  • pipettes;
  • wood­en stick;
  • Petri dish;
  • sodi­um hy­drox­ide so­lu­tion.

Step-by-step in­struc­tions

A few egg whites are sep­a­rat­ed from their yolks and a few drops of cop­per(II) sul­fate so­lu­tion are added. Light blue threads form in the mix­ture. The mix­ture is poured into a Petri dish and some sodi­um hy­drox­ide so­lu­tion is added – and the mix­ture turns pur­ple!

Process de­scrip­tion

Egg white con­tains oval­bu­min pro­tein. Cop­per(II) sul­fate forms an in­sol­u­ble com­pound with it, which cre­ates the light blue threads you ob­serve. When sodi­um hy­drox­ide is added, the cop­per and oval­bu­min com­pound breaks down into small­er mol­e­cules, which give the so­lu­tion its pur­ple col­or.

A safer ver­sion of this ex­per­i­ment is in­clud­ed in the “Chem­istry of eggs” set from the MEL Chem­istry sub­scrip­tion.