How Would You Test an Unknown Solution for Sugar?
In food chemistry, there are chemical reagents that can be used to test a solution to see if it contains sugar. In particular, simple sugars, such as glucose and fructose, can be detected by a solution called Benedict's reagent. When the reagent is added to a liquid solution and heated by being immersed in a boiling water bath, it will chemically react with the sugar and will visibly change color. You can test an unknown solution for sugar with Benedict's reagent.
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Things You'll Need
- Safety goggles
- Graduated cylinder, 10-milliliter
- Test tube
- Beaker, 1,000-milliliter
- Hot plate or Bunsen burner with tripod beaker holder
- Benedict's reagent solution
- Test-tube tongs
Instructions
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Measure 4 milliliters of the unknown solution with the graduated cylinder. Pour the solution into a test tube. Measure 1 milliliter of Benedict's solution, and add it to the unknown solution. Hold onto the test tube near the top, and swirl the liquid inside of it to mix it together. Set it aside in a test-tube holder.
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Fill a 1,000-milliliter beaker with water. Place the test tube in it to ensure that the water level is high enough to cover the solution, but not so high as to be displaced and spill out of the beaker. Place the beaker onto a hot plate or over a lit Bunsen burner with a tripod beaker holder set over it. When the water begins to boil, use a set of test-tube tongs to pick up the test tube and insert it into the water, bottom first.
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Monitor the unknown solution as it is immersed in the boiling water bath while still in the test tube for 10 minutes. If the solution contains sugar, it will change color. The Benedict's test reagent is blue. If the solution changes from blue to brown, red, orange, yellow or green, it means that the unknown solution has sugar in it.
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Tips & Warnings
Take care when handling hot plates, open flames or boiling water, as they can burn.
