Expert: Walter Hintz - 10/4/2005

Question
Hello, Walter Hintz,

I have scoured my lab manuel and text and just cant find the answer so I need guidance and assistance. (though if murphey's law prevails the answr is under my nose.

Here is the question:

A test tube contains starch, hydrochloric acid, and water.  The buiret test is negative. Explain then it goes on to ask ... After 30 minutes the Benedict's test is positive...

It is that it take the proper amount of time to change the starch into a sugar? HELP!!!

Answer
There is something wrong here.  You first mention biuret and then benedicts.  Biuret tests for protein so I assume that you meant benedicts.  It appears that after 30 minutes the HCl broke down the starch into sugar.  You were right.  The answer was right under your nose.