Analysis Of Phosphoriic Acid In Soft Drinks

PROCEDURE

DETERMINATION OF PHOSPHORIC ACID IN THE SOFT DRINKS
Black coloured soft drinks such as Coke from Coca Cola and Pepsi contains Phosphoric Acid in them. An experiment will be conducted here to determine the quantity of Phosphoric Acid content in the black coloured soft drinks.

In the beginning of the experiment the preparation and standardization of a base solution will be made.

Materials Required:
1. Pellets of Sodium Hydroxide (NaOH)
2. Phenolphthalein solution (1%)
3. Potassium acid phthalate (KHC8H4O4)
4. Graduated cylinder - 10 mL
5. Buffer solutions of pH 4 and 7
6. Graduated cylinder - 100 mL
7. Volumetric flask with stopper - 250 mL
8. Two 100-mL beakers
9. Two 50-mL Burettes
10. Two Small funnels so that they fit into

The drop rate was adjusted to 1 to 2 drops/second. 10.0 mL of the NaOH solution was allowed to drip away into a waste beaker. The exact volume of the sodium hydroxide solution used was determined. A clean 250-mL beaker was taken and around 0.3 to 0.5 g of potassium acid phthalate was weighed into it. 50 mL of distilled water was approximately added to this 250 mL beaker and gently swirled so that the solid (potassium acid phthalate) got fully dissolved into the water. 2 drops of phenolphthalein indicator solution was added to the beaker. The pH electrode was calibrated using the pH buffers. For this, 25 mL of pH 4 and pH 7 buffers were taken in 50 mL or 100 mL beakers. The buffer solutions were saved in case the electrode needed to be re-calibrated later on. The potassium acid phthalate solution was titrated with 0.1 M NaOH. The solution turned red when it reached the end point. The titration was continued for 10 seconds after a permanent red color was obtained. The volume of 0.1 M NaOH solution used was determined. The 250 mL beaker was rinsed well with the distilled water. The titration procedure above was repeated 2 more times with fresh potassium acid