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What it is. This EDTA titrant contains 0.1 mole of disodium EDTA dihydrate per liter, labeled 0.2 N, and is supplied in a 1-gallon size. It is a clear, colorless complexometric titrant for samples with relatively high metal content.
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Why 0.1 M is labeled 0.2 N. EDTA binds divalent metals one-to-one, and each mole corresponds to two equivalents of charge, so 0.1 M EDTA equals 0.2 N. Calculations are simplest in molarity, since one mole of EDTA complexes one mole of metal.
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What each milliliter delivers. One milliliter contains 0.1 millimole of EDTA, which complexes 4.008 mg of calcium, 2.431 mg of magnesium, 6.538 mg of zinc, or the equivalent of 10.01 mg of calcium carbonate (calculated from atomic weights).
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Built for concentrated samples. At 0.1 M, the titrant keeps volumes practical for plating baths, metal finishing solutions, mineral and cement samples, and concentrated process streams, where weaker titrants would require impractically large volumes.
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Calcium alone versus total hardness. To determine calcium separately, methods raise the sample pH to about 12 with sodium hydroxide so magnesium precipitates as hydroxide, then titrate with a calcium-selective indicator such as murexide. The difference between total hardness and calcium gives magnesium.
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Running the titration. Choose the indicator and pH for the metal: Eriochrome Black T near pH 10 for calcium plus magnesium, or metal-specific indicators for zinc, nickel, or copper. Lab Pro offers Eriochrome Black T Indicator and the ammonia buffer components Ammonium Chloride, ACS Grade, and Ammonium Hydroxide 28 to 30% Solution, ACS Grade.
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How EDTA works. EDTA is a hexadentate chelating agent: two nitrogen atoms and four carboxylate groups bind each metal ion in a stable, water-soluble one-to-one complex, giving the sharp, stoichiometric endpoints complexometric methods rely on.
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Gallon size for high-volume labs. The 1 gallon size supports production and QC labs that titrate daily, providing one consistent lot over a long period. The same strength is also available in a 1 liter size as EDTA Disodium Solution, 0.1 M (0.2 N).
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Standardization and care. Standardize against calcium carbonate or zinc for critical work, keep the container closed to prevent evaporation, and use deionized water and metal-free labware for all dilutions and rinses.
Technical Specifications
| Chemical Name |
Ethylenediaminetetraacetic acid disodium salt dihydrate, aqueous solution |
| Synonyms |
EDTA titrant, disodium EDTA solution |
| 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) |
| EDTA per mL |
0.100 mmol |
| Titration Equivalence |
1.00 mL = 4.008 mg Ca, 2.431 mg Mg, 6.538 mg Zn, or 10.01 mg CaCO3 (calculated) |
| Binding Ratio |
1:1 EDTA to metal ion |
| Density |
About 1.02 to 1.03 g/mL |
| Appearance |
Clear, colorless liquid |
| Physical State |
Liquid, aqueous solution |
| Storage |
Room temperature, tightly closed |
| Package Size |
1 gallon |
Applications / Common Uses
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Plating bath analysis: Determines zinc, nickel, and copper in plating solutions.
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Concentrated hardness samples: Titrates calcium and magnesium at high levels.
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Mineral and cement testing: Measures calcium in high-calcium samples.
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Process QC: Monitors metal content in production streams.
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Chelating stock: Supplies a ready 0.1 M EDTA for buffer additions.
Storage, Handling & Shipping
Store the solution tightly closed at room temperature to prevent evaporation, which would raise its concentration. Keep it away from strong oxidizers and metal-containing materials, and use clean, metal-free labware so trace metals do not consume 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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