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Paraquat Dichlorid |
| Chemical name: |
1,1’-dimethyl-4,4’-bipyridinium dichloride |
| Molecular weight: |
257.16
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| Molecular formular: |
C12H14Cl2N2 |
Molecular structure: |
 |
Mode of action: |
Non-selective contact herbicide, absorbed by the foliage, with some translocation in the xylem |
Uses: |
Broad-spectrum control of broad-leaved weeds and grasses in fruit orchards (including citrus), plantation crops(bananas, coffee, cocoa palms, coconut palms, oil palms, rubber, etc), vines, olives, tea, alfalfa, onions, leeks, sugar beet, asparagus, ornamental trees and shrubs, in forestry, etc. Also used for general weed control on non-crop land; as a defoliant for cotton and hops; for destruction of potato haulms; as a desiccant for pineapples, sugar cane, soya beans, and sunflowers; for strawberry runner control; in pasture renovation; and for control of aquatic weeds. For control of annual weeds, applied at 0.4-1.0 kg/ha. |
Physical chemistry: |
Form Colourless, hygroscopic crystals. Melting Point: Decomposes at c. 340℃. Vapour Pressure<1×10-2 mPa (25℃). Kow logP=-4.5 (20℃). Henry <4×10-9 Pa m3 mol-1(calc.). S.g./density 1.24-1.26 (20℃). Solubility In water c. 620 g/l(20℃). Practically insoluble in most organic solvents. Stability Stable in neutral and acidic media. But readily hydrolysed in alkaline media. Photochemically decomposed by u.v. irradiation in aqueous solution. |
Mmmalian toxicology: |
Oral Acute oral LD50 for rats 157-129, guinea pigs 30-58 mg/kg. Skin and eye Acute percutaneous LD50 for rats 911 mg paraquat ion/kg. Irritating to skin and eyes (rabbits). Absorption through intact human skin is minimal; exposures can cause irritation and a delay in the healing of cuts and wounds; can cause temporary damage to nails. Not a skin sensitizer (guinea pigs). Inhalation No vapour toxicity. Extreme exposure to spray droplets may cause nose bleeding. NOEL (1 y) for dogs 0.65 mg/kg b.w. daily; (2 y) for rats 1.7mg/kg b.w.daily. ADI (JMPR) 0.004 mg/kg b.w. (as paraquat ion) [1986]. Toxicity class WHO (a.i.) II; EPA (formulation) II (oral, a.i.); III (dermal, a.i.) EC hazard T; R24/25 Xi; R36/38 (applies to all salts) |
Ecotoxicology: |
Birds Acute oral LD50 for bobwhite quail 175,mallard ducks 199 mg/kg. LC50 (5 d) for bobwhite quail 981,Japanese quail 970, mallard ducks 4048, ring-necked pheasants 1468 mg/kg. Fish LC50 (96 h) for rainbow trout 26, mirror carp 135 mg/l. Daphnia EC50 (48 h) 6.1 mg/l. Algae EbC50 (96 h) 0.10 mg/l; ErC50 0.28 mg/l. Bees LD50 for (72 h) (oral) 36 ug/bee;(contact) 150 ug/bee. Worms LD50>1380 mg/kg soil. |
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