Biuret Test Results

 

The following were tested for protein with the Biuret Test:

 

TT#1   Distilled Water

TT#2   Egg albumin

TT#3   Glucose

TT#4   Starch

TT#5   pepsin

TT#6   Potato extract

TT#7   milk

TT#8   corn flakes

TT#9   bread

TT#10 unknown

 

Which of the samples contains protein as indicated by a positive Biuret test?

 

What is the function of test tube #1 ?