Using Chemical Indicators Lab

In this lab, you will1. Learn the names of specific indicators2. Learn the what a specific indicator test for3. Be introduced to three organic compounds,

proteins, carbohydrates and lipids

Biuret Solution Blue Color ? Protein present

Benedict’s SolutionBlue Color ? monosaccharide

Iodine SolutionOrange or Brown ? polysaccharide

All three indicators show a color change when mixed with a specific organic compound.

Chemical Indicators

Iodine

Chemical Indicators for Carbohydrates: Initial Color

Chemical Indicator for Protein: Initial Color

Negative Control Test Tubes: Indicator + Water

Positive Control Test Tubes: Indicator + Organic Compound

Negative Benedict’s

PositiveBenedict’s

NegativeIodine

Positive Iodine

Test Tube #

Organic CompoundSolution

Indicator Initial Color Final Color

1 Monosaccharide Iodine  orange/brown  orange/brown

2 Disaccharide Iodine  orange/brown  orange/brown

3 Polysaccharide Iodine  orange/brown  blue-black

4 Protein Biuret Solution  blue  purple

Tube # Organic CompoundSolution

Indicator Initial Color

Final Color

Location ofColor

1 Monosaccharide Benedict’s Solution  blue  orange  NA

2 Disaccharide Benedict’s Solution  blue  blue  NA

3 Polysaccharide Benedict’s Solution  blue  blue  NA

4 Vegetable Oil Sudan Red      

1. Which two indicators test for a carbohydrate?2. Which indicator checks for a protein?3. If a monosaccharide is present in the food, what

indicator turns orange?4. If a polysaccharide is present in the food, what

indicator turns blue-black?5. What is observed with a positive test for proteins?6. What would happen to the Iodine if you mixed it

with water? Why?7. Which indicator has to be heated before a change

occurs?8. Name all the organic compounds tested in the lab.

Check Your Understanding

Sudan Red: No Color Change Indicator

Sudan Red Test

The more red; the more lipid present.