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Physical Properties
Molecular weight:221.0g/mol. Physical form:Colourless powder, with a slight phenolic odour. Density: 0.7-0.8; Composition:Tech. is 96% pure. Melting point:140.5℃; Vapour pressure:1.86 × 10-2 mPa(25℃, OECD 104); Henry constant:1.32 × 10-5 Pa m3 mol-1 (calc.); Partition coefficient(n-octanol and water):logP = 2.58-2.83 (pH 1), 0.04-0.33 (pH 5); pKa:2.73. Solubility:In water 311 (pH 1), 20 031 ( pH 5), 23 180 (pH 7), 34 196 (pH 9) (all in mg/l, 25℃). In ethanol 1250, diethyl ether 243, heptane 1.1, toluene 6.7, xylene 5.8 (all in g/; Stability:2,4-D is a strong acid, and forms water-soluble salts with alkali metals and amines. Hard water leads to precipitation of the calcium and magnesium salts, but a sequestering agent is included in formulations to prevent this.
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Toxicology
Oral:Acute oral LD50 for rats 639-764(699) mg/kg, mice 138 mg/kg. Isopropyl: 700 mg/kg. Sodium Salt: 500-805 mg/kg. Dimethylamine salt: 949 mg/kg. Isooctyl ester: 896 mg/kg. Percutaneous: Acute percutaneous LD50 for rats >1600, rabbits >2400 mg/kg. Skin and eye irritant (rabbits). Not a skin sensitiser (guinea pigs). Inhalation: LC50(24 h) for rats >1.79 mg/l. Phytotoxicity: Phytotoxic to most broad-leaved crops, especially cotton, vines, tomatoes, ornam
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Environmental Profile
Ecotoxicology:
Algae:EC50(5 d) for Selenastrum capricornutum 33.2 mg/l. Bees:Not toxic to bees; LD50(oral) 104.5 mg/bee.Birds:Acute oral LD50 for wild ducks >1000, Japanese quail 668, pigeons 668, pheasants 472 mg/kg. LC50 (96 h) for mallard ducks >5620 mg/l.Daphnia:LC50(21 d) 235 mg/l. Fish:Some formulations (e.g. esters) are toxic to fish, whilst others are not. LC50(96 h) for rainbow trout >100 mg/l. Worms:LC50 (7 d) 860 mg/kg; NOEC (14 d) 100 g/kg.Other aquatic spp.:EC50(14 d) for Lemna gibba 0.58 mg/l.Other beneficial spp.:Harmless to Trichogrammia cacoeciae, Poecilus cupreus, Aleochara bilineata.?
Environmental fate:
EHC 84 concludes that, when used as recommended, 2,4-D does not appear to produce direct toxic effects on any animal species.Animals:In rats, following oral administration, elimination is rapid, and mainly as the unchanged substance. Following single doses of up to 10 mg/kg, excretion is almost complete after 24 hours, although, with higher doses, comp Soil:In soil, microbial degradation involves hydroxylation, decarboxylation, cleavage of the acid side-chain, and ring opening. Half-life in soil <7 d. Koc c. 60. For a review of environmental aspects of 2,4-D. Plant: In plants, metabolism involves hydroxylation, decarboxylation, cleavage of the acid side-chain, and ring opening.
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Transport Information
Hazard Class:II (Moderately hazardous)