Pure paraquat salts are white and the technical products yellow. They are crystalline, odourless, hygroscopic powders with a relative molecular mass of 257.2 for paraquat dichloride and 408.5 for paraquat dimethylsulfate. The relative molecular mass of the paraquat ion is 186.2 (Summers, 1980). Some of the other physical properties of paraquat dichloride, the salt most used fo