What is a Fehling's test?

In chemistry, scientists commonly use a Fehling's test to reduce sugars. To perform this test, the scientist uses both Fehling's B and Fehling's A solutions. The A solution is dilute sulfuric acid, distilled water and copper sulfate III, and the B solution is distilled water, potassium tartrate and sodium hydroxide.

To perform the test, the scientist mixes 15 milliliters of both the A solution and the B solution. They add 2 milliliters of this mixture to a test tube and then put 3 drops of what they are testing into the tube. The tube goes into a 140 degrees Fahrenheit water bath to complete the test.