0.05 M EDTA Solution Preparation & Standardization

0.05 M EDTA Solution

Preparation of 0.05 M EDTA Solution

• Dissolve 18.6 g of disodium ethylenediaminetetraacetate dihydrate (EDTA)(C10H14N2Na2O8·2H2O)13 in sufficient water to make 1000 mL, and store in a polyethylene container.

Standardization of 0.05 EDTA Solution

• Weigh accurately about 200 mg of calcium carbonate14 transfer to a 400-mL beaker, add 10 mL of water, and swirl to form a slurry.
• Cover the beaker with a water glass and introduce 2 mL of hydrochloric acid (HCl, 3 :10) from a pipet inserted between the lip of the beaker and edge of the watch glass.
• Swirl contents of the beaker to dissolve the calcium carbonate.
• Wash down the sides of the beaker, the outer surface of the pipet, and the watch glass, and dilute to about 100 ml. While stirring the solution, preferably with a magnetic stirrer,
• Add about 30 mL of the disodium ethylenediaminetetraacetate (EDTA) solution from a 50-mL burette.
• Add 15 mL of sodium hydroxide solution (NaOH, 40 g/L), 300 mg of hydroxy naphthol blue indicator, and continue the titration with the disodium ethylenediaminetetraacetate (EDTA) solution to a blue endpoint.

Calculation

Calculate the molarity of the disodium ethylenediaminetetraacetate solution as follows:
M = W / 100.09 * V
where:
M = molarity of the disodium ethylenediaminetetraacetate solution,
W = milligrams of CaCO3 in the sample of calcium carbonate taken, and
V = milliliters of disodium ethylenediaminetetraacetate solution consumed.