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I offer a slight modification of a very old method of determining the end-reaction of the quantitative determination of glucose in the urine. In the experience of every one who has used Fehling's solution in the quantitative determination of glucose and tried to make up his mind when the reaction is complete by the disappearance of the blue color of the solution, it must be impressed on him how hard it is to say at just what point the "blue" all disappears and when the solution becomes clear, which is recommended in most text-books on the subject as the final step.
The chemical reaction for determining this end-reaction is given to us as follows: Remove a small portion of the mixture (of Fehling's solution and urine) contained in the beaker (in a test-tube), add a few drops of acetic acid and then a few drops of potassium ferrocyanid. If the
Jacobs FB. DETERMINATION OF END-REACTION IN ESTIMATION OF GLUCOSE. JAMA. 1912;LIX(6):440-441. doi:10.1001/jama.1912.04270080122015