Define Sample Titration for Fehling Soxhlet Method
Dilute the given sample glucose solution in 100 ml volumetric flask to the mark with distilled water. Pipette 5 ml of Fehling's A and and 5 ml of Fehling B solution into a 100 ml conical flask. Add 4-5 ml of the diluted sugar solution from the burette and heat over a wire gauze until the solution starts boiling. Boil for about 15-25 seconds and add further amounts of sugar solution in small volumes until only a faint blue colour is seen. Add 1 ml of 0.2% methylene blue solution. Continue heating and complete the titration by adding sugar solution drop by drop ensuring that there is a few seconds of gap between each addition so that the titration doesn't go beyond three minutes.
The contents of the conical flask should be continuously boiling during the titration. This is a pilot reading and it will be slightly higher than the actual titer value. For the subsequent readings, add sugar solution 1 ml less than the amount required to reduce 10 ml of Fehlings's solution (this will be 1 ml less than pilot reading). Heat the mixture to boiling point over a wire gauze and continue boiling for two minutes. Without removing the burner add 1 ml of methylene blue solution and complete the titration within another minute by adding small amounts of sugar solution (2-3 drops) at a time till the end point is reached. Repeat the titrations till concordant titer values are obtained. Calculate the amount of glucose present in the given sample solution.