How to Prepare a Standard EDTA Solution

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When converted to a standard solution, EDTA is a useful chemical compound for titration applications such as determining the metallic content of various solutions.

Step 1: Dry and cool
Measure 4 grams of purified dihydrate ethylenediaminetetraacetic acid on the balance and dry at 80 degrees Celsius for one hour before letting it cool to room temperature in the desiccator.

Tip
The salt will contain about 0.3 percent moisture after drying and cooling. Make a note to correct the salt's weight in your calculation of the molarity of the finished solution.

Step 2: Measure
Weigh 3.8 grams and transfer it into a volumetric flask using a powder funnel.

Step 3: Add water
Rinse the funnel by pouring a small amount of distilled or deionized water through it before removing the salt. Then add enough extra purified water to make 700 milliliters. Use a dry, uncontaminated container with a non-glass stopper.

Step 4: Mix
Swirl the solution until all of the powder has dissolved.

Tip
Be patient -- it may take up to 15 minutes for the solution to be completely dissolved.

Step 5: Add water and mix
Add more purified water until it reaches the 1-liter mark, and mix well.

Step 6: Calculate molarity
Calculate the molarity, or molar concentration, of the solution. The result should be at or very close to 0.01 M.

Step 7: Finish
Store the solution with a stopper. If you plan to use it for titration, it's good practice to conduct the experiment while the solution is still fresh.

Did You Know?
EDTA was first used as a medical treatment for heavy metal poisoning in the 1940s, and is still FDA-approved for that purpose.

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