Potsssium salts of fatty acids are commonly called soap salts. they are used in insecticides, herbicides and fungicides. They are produced by adding potassium hydroxide to fatty acids found in animal fats and plant oils. They are often ready to use produts found at the garden center either as a ready to use sprya or in concentrate that yo mix with water. common ones include safer moss and algae control, insecticidal soaps and safer weed and grass killer.