Insecticidal soap's active ingredient is most often a potassium salt of fatty acids. Insecticidal soap should be based on long-chain fatty acids (10–18 carbon atoms), because shorter-chain fatty acids tend to be damaging for the plant (phytotoxicity). Short (8-carbon) fatty-acid chains occur for example in coconut oil and soaps based thereon. "'Green Soap' is a potassium/coconut oil soap ... has also been shown to be effective, as an unlabeled insecticide, in controlling soft-bodied insects including aphids". Recommended concentrations of insecticidal soap are typically in the range 1–2 percent soap mixed with water. One manufacturer recommends a concentration of 0.06% to 0.25% (pure soap equivalent) for most agricultural applications.; another one recommends concentrations of 0.5 to 1% pure soap equivalent. In the European Union, fatty acid potassium salts are registered and allowed as insecticide at a 2% concentration.