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What it is. This EDTA disodium solution contains 0.1 mole of ethylenediaminetetraacetic acid disodium salt dihydrate (disodium EDTA) per liter (0.2 N) and is supplied in a 1 L size. It is a clear, colorless titrant for complexometric titrations and a ready-made chelating solution.
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Chemical identity. Disodium EDTA dihydrate (CAS 6381-92-6, C10H14N2Na2O8·2H2O, 372.24 g/mol) is the most widely used form of EDTA for preparing volumetric solutions. A 0.1 M solution contains about 37.2 g of the dihydrate per liter, roughly 3.7% by weight.
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Why 0.1 M is also 0.2 N. EDTA binds most metal ions in a one-to-one ratio. When normality is expressed for divalent ions such as calcium, magnesium, and zinc, each mole of EDTA reacts with two equivalents of charge, so a 0.1 M solution is labeled 0.2 N. Molarity is the more direct basis for calculations, since one mole of EDTA complexes one mole of metal.
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How EDTA works. EDTA is a hexadentate chelating agent: its two nitrogen atoms and four carboxylate groups wrap around a metal ion, forming a stable, water-soluble complex. That strong, predictable binding is what makes EDTA titrations accurate and what lets EDTA sequester metal ions in buffers and cleaning formulations.
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Complexometric titration. In a typical titration, you add EDTA to a sample buffered to the right pH with a metal indicator. For calcium and magnesium, an ammonia buffer near pH 10 with Eriochrome Black T gives a wine-red to blue endpoint. Lab Pro offers Eriochrome Black T Indicator, Ammonium Chloride, ACS Grade, and Ammonium Hydroxide 28 to 30% Solution, ACS Grade for that buffer system.
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Why 0.1 M strength. A 0.1 M EDTA solution suits samples with relatively high metal content, such as metal assays, plating baths, and concentrated hardness samples, where weaker titrants would require impractically large volumes. For dilute samples, Lab Pro also offers EDTA Titrant 0.1 N / 0.05 M and, in larger volumes, EDTA Titrant 0.2 N / 0.1 M, 1 gallon.
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Chelating uses beyond titration. Add disodium EDTA to buffers and reagents to bind trace metal ions that would otherwise catalyze unwanted reactions, inhibit metal-dependent enzymes, and prevent scale in cleaning solutions. A ready-made 0.1 M stock allows quick, accurate additions.
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Standardization and care. For the most accurate results, standardize EDTA against a primary standard such as calcium carbonate or zinc before critical work, and store it tightly closed to prevent evaporation from changing its concentration. Use deionized water for all dilutions to avoid introducing calcium or magnesium.
Technical Specifications
| Chemical Name |
Ethylenediaminetetraacetic acid disodium salt dihydrate, aqueous solution |
| Synonyms |
Disodium EDTA, EDTA-Na2, edetate disodium |
| CAS Numbers |
6381-92-6 (disodium EDTA dihydrate); 7732-18-5 (water) |
| EC Number (active) |
205-358-3 |
| Formula (active) |
C10H14N2Na2O8·2H2O |
| Molecular Weight (active) |
372.24 g/mol |
| Concentration |
0.1 M (0.2 N) |
| EDTA Content |
About 37.2 g/L dihydrate, about 3.7% (calculated) |
| Appearance |
Clear, colorless liquid |
| Density |
About 1.02 to 1.03 g/mL |
| Alternate CAS (anhydrous disodium salt) |
139-33-3 |
| Free-Acid CAS (reference) |
60-00-4 |
| EDTA per mL |
0.100 mmol |
| Titration Equivalence |
1.00 mL = 4.008 mg Ca, 2.431 mg Mg, or 10.01 mg CaCO3 (calculated) |
| Binding Ratio |
1:1 EDTA to metal ion |
| Physical State |
Liquid, aqueous solution |
| Boiling Point |
About 100 °C |
| Storage |
Room temperature, tightly closed to prevent evaporation |
| Package Size |
1 L |
Applications / Common Uses
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Complexometric titration: Determines calcium, magnesium, zinc, and other metals.
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Metal assays: Quantifies metal content in plating baths and process solutions.
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Water hardness: Titrates concentrated hardness samples with Eriochrome Black T.
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Chelating additive: Binds trace metals in buffers and reagents.
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Enzyme inhibition: Removes metal cofactors to stop metal-dependent enzyme activity.
Storage, Handling & Shipping
Store the solution tightly closed at room temperature, protected from evaporation, which would raise its concentration. Keep it away from strong oxidizers and metal-containing materials, and use clean, metal-free labware to avoid consuming EDTA before titration.
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Incompatible materials: Strong oxidizers, strong acids, and metal salts.
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Personal protection: Safety glasses and nitrile gloves.
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Spill response: Absorb with inert material and rinse the area with water.
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First aid: Eyes: rinse with water for several minutes. Ingestion: rinse mouth and seek medical advice.
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