hygroscopic crystals which decompose at 300°C. It is practically non-volatile with a vapour pressure of 0.1 mPa. It is very soluble in water (700 g/l at 20°C) and practically insoluble in most other organic solvents. It is stable in neutral and acidic media, but readily hydrolysed in alkaline media. Paraquat is photochemically decomposed by ultraviolet radiation in aqueous solution.