Ethylenediaminetetraacetic acid

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Ethylenediaminetetraacetic acid
Ethylenediaminetetraacetic acid EDTA sample.jpg
EDTA sample on a watchglass
Names
Systematic IUPAC name
2,2',2,2'-(Ethane-1,2-diyldinitrilo)tetraacetic acid
Other names
EDTA
N,N'-Ethane-1,2-diylbis[N-( carboxymethyl)glycine]
Fiaminoethane-tetraacetic acid
Edetic acid
Ethylenedinitrilo-tetraacetic acid
Versene
Properties
C10H16N2O8
Molar mass 292.24 g/mol
Appearance Colorless crystalline solid
Density 860 g/cm3 (at 20 °C)
Melting point 240 °C (464 °F; 513 K) (decomposes; decomposition begins above 150 °C)
Boiling point Decomposition
0.0162 g/100 ml (2.7 °C)
3.8 g/100 ml (25 °C)
9.381 g/100 ml (100 °C)
Solubility Soluble in aq. alkali
Vapor pressure 1.5·10-12 mmHg (25 °C)
Acidity (pKa) 1.782
Thermochemistry
−1.7654 to −1.7580 MJ/mol
Hazards
Safety data sheet Sigma-Aldrich
Lethal dose or concentration (LD, LC):
1000 mg/kg (oral, rat)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Ethylenediaminetetraacetic acid (more commonly EDTA) is a chemical compound with a variety of uses, in both chemistry and medicine, due to its ability to sequester metal ions.

Properties

Chemical

EDTA usually binds to a metal cation through its two amines and four carboxylates.

Physical

EDTA is an odorless white solid, soluble in water.

Availability

EDTA is available as both free acid or more commonly as disodium or tetrasodium salt. Chelated fertilizers have EDTA in their composition, but extraction may not worth the effort if they're too diluted.

Preparation

EDTA can be prepared by reacting ethylenediamine with chloroacetic acid.

Instead of chloroacetic acid, a mixture of formaldehyde and sodium cyanide can be used.

Projects

  • Removal of heavy metals such as lead and mercury
  • Determining water hardness
  • Preservative

Handling

Safety

EDTA isn't harmful to touch, though ingestion of large doses may lead to hypocalcaemia, due to the EDTA removing the Ca2+ ions from blood. Iron and other metals will also be removed, which may lead to mineral deficiency.

EDTA has low cytotoxic and genotoxic effect.

Storage

EDTA should be stored in closed bottles, away from corrosive reagents. Plastic bottles are suitable.

Disposal

EDTA has low environmental impact, so it can be safely poured down the drain, though if it's binded to toxic metals, it may be a hazard to the environment and instead should be taken to hazardous waste disposal facilities.

References

Relevant Sciencemadness threads