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Chromium(III)

Copper(II)

Iron(II) and Iron(III)

Zinc(II) and Aluminium(III)

Nickel(II)

Manganese(II)

Cobalt(II)

EDTA

EDTA (Ethylenediaminetetraacetic acid)

EDTA is a versatile, synthetic, and water-soluble organic compound that forms strong complexes with metal ions through a process known as chelation. Its chemical structure consists of four carboxyl (COOH) groups and two amine (NH2) groups arranged around a central carbon atom. This structure allows EDTA to coordinate with metal ions by forming multiple bonds, creating a stable complex.

Usefulness as a Chelating Agent:

EDTA’s ability to form stable complexes with metal ions makes it invaluable in various applications, including:

  1. Metal Ion Removal: EDTA is used in analytical chemistry and water treatment to remove metal ions from solutions, such as the removal of calcium and magnesium ions that can cause water hardness.

  2. Medicine:

    • Treatment of Heavy Metal Poisoning: EDTA is employed as a chelating agent to treat heavy metal poisoning, such as lead or mercury poisoning. When administered intravenously, EDTA can bind to these toxic metal ions in the bloodstream, forming water-soluble complexes that are excreted in urine. This helps remove the toxic metals from the body.
    • Anticoagulant: EDTA is also used as an anticoagulant in blood collection tubes, preventing blood from clotting by chelating calcium ions, which are essential for the clotting process.

  3. Food and Beverage Industry: EDTA is used as a food preservative to prevent the oxidation of food products and to maintain their colour and flavour by binding to metal ions that can catalyse oxidation reactions.

  4. Cosmetics and Pharmaceuticals: EDTA is included in many cosmetic and pharmaceutical products as a stabilizer to maintain the product’s quality and shelf life by chelating metal ions that could catalyse chemical degradation reactions.

  5. Detergents: EDTA is used in detergents to improve their cleaning efficiency by sequestering metal ions that can interfere with the detergent’s cleaning action. This helps prevent the formation of scum and the re-deposition of dirt on fabrics.

Use in Medicine for Poisoning and Strokes:

  • Treatment of Heavy Metal Poisoning: EDTA is used medically in cases of heavy metal poisoning, such as lead, mercury, or cadmium poisoning. It is administered intravenously, and the chelation therapy with EDTA helps to reduce the concentration of toxic metals in the body, preventing further damage and promoting their excretion through urine.

  • Potential Use in Stroke Treatment: While EDTA’s primary role is in metal chelation, there is ongoing research exploring its potential use in stroke treatment. Some studies suggest that EDTA might have neuroprotective effects by reducing oxidative stress and inflammation. However, this application is still in the experimental stage, and more research is needed to establish its effectiveness.

In summary, EDTA is a versatile chelating agent with a wide range of applications, including the treatment of heavy metal poisoning and potential applications in medicine, such as stroke treatment. Its ability to form stable complexes with metal ions makes it a valuable tool in various industries and medical treatments.

 

Complexometric Titration.

Buffered at pH 10

Eriochrome Black T indicator

Complexometric Titration of Calcium and Magnesium Ions in Hard Water Using EDTA

1. Sample Preparation:

  • Collect a representative sample of hard water.
  • Adjust the pH of the sample to a suitable range (usually around pH 10) using a buffer solution to ensure the stability of the EDTA complexes.

2. Titration Setup:

  • Prepare a standardized solution of EDTA. This solution is typically made by dissolving EDTA in distilled water and adding a small amount of a buffer and an indicator
    (e.g., Eriochrome Black T shown to the left).
  • Fill a burette with the standardized EDTA solution.
  • Add a few drops of the indicator to the sample of hard water. The indicator will change color when all the calcium and magnesium ions have formed complexes with EDTA.

3. Titration Procedure:

  • Slowly add the EDTA solution from the burette to the sample while stirring continuously.
  • Initially, the indicator will change colour from the original colour to a wine-red or violet colour as the EDTA complexes with calcium and magnesium ions.
    Mg²⁺ (aq)  +  EDTA⁴⁻(aq)   →   [Mg-EDTA]²⁻ (aq)
  • Continue adding the EDTA solution until the colour change becomes permanent, indicating that all calcium and magnesium ions have formed complexes with the EDTA.

4. Calculation:

  • Calculate the concentrations of calcium and magnesium ions in the hard water based on the volume and molarity of the EDTA solution used in the titration.
  • Use stoichiometric ratios to determine the concentration of each ion separately.

5. Results:

  • Report the concentrations of calcium and magnesium ions in the hard water in the appropriate units (e.g. mg/dm 3 or ppm).

In this complexometric titration, EDTA forms stable complexes with calcium and magnesium ions, effectively “capturing” them and removing them from the solution. The endpoint of the titration is reached when all calcium and magnesium ions are complexed with EDTA, resulting in a color change due to the indicator used. By knowing the volume and concentration of the EDTA solution added, you can calculate the concentrations of calcium and magnesium ions in the hard water sample.

 

 

 

Another video showing
the EDTA titrations for
Mg 2+ and Ca 2+ concentrations
in water ⇒

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