How to Test for Glycerin

A couple of simple chemicals are needed to test for glycerin.

Glycerin, a simple polyol (sugar alcohol) compound also called glycerine and glycerol, is commonly found in pharmaceuticals (primarily to help smoothness), botanical extracts, anti-freeze and food products (as a sweetening substitute for sucrose). In foods, glycerin is classified as a carbohydrate and has a calorie count near that of table sugar. Testing for glycerin requires only two chemicals added to a dissolved sample of the test subject. It is then heated, and you observe the color of the resulting compound.

Things You'll Need

• Graduated pipette
• Large test tube
• Bunsen burner
• Catechol
• Sulfuric acid
• Purified water
• Flask
• Test substance

Instructions

1. Dissolve a sample portion of the test substance in purified water. If testing a food product, make sure the substance is pureed. Make sure that the mixture is completely liquefied, with no large pieces contained in it. Measure 3 ml of the substance with the graduated pipette and add it to the test tube.

2. Create a solution of purified water and catechol, adding 1 part catechol to 9 parts water. Mix the solution until the catechol is completely dissolved. Measure 3 ml of the solution with the graduated pipette and add that to the test tube with the sample.

   Catechol is an organic compound that occurs in trace amounts in nature but is mass-produced as a precursor to flavors, pesticides and fragrances. Normally colorless, catechol changes color when in the presence of certain other chemicals. Catchol is available through chemical companies, such as CJP Chemical and Sigma-Aldrich.

3. Add 6 ml of sulfuric acid, using the graduated pipette, to the test tube with the sample and catechol solution.

4. Fill the flask with water, and place the test tube inside the water.

5. Heat the flask and test tube over the Bunsen burner for 30 minutes. The water should be boiling as the tube is heated.

6. Examine the mixture contained in the test tube. The sample will turn an orange-red color if the glycerin is present in the solution.

Tips & Warnings

• Use caution with heating equipment and sulfuric acid, as mishandling of either can result in personal injury.

References

• All About Feed: Tests Show Glycerin Close to Corn
• Pub Med: The importance of glycerin-containing negative control tests in allergy research studies that use intradermal skin tests.
• Utah Biodiesel Supply: Biodiesel Testing
• Flinn Scientific Inc.: Catechol

Resources

• CJP Chemical
• Sigma-Aldrich