Ash is the substance that remains after an organic substance has been burned. The word ashes usually refers to the minerals obtained from burning coal, wood, or other fuels. An analysis of the ashes of burned foods and other substances can determine the minerals they contain. For example, chemical tests of the ashes of burnt milk show that they contain calcium. Seaweed ash has a high iodine content. Some kinds of ashes can be used for various purposes. For example, fly ash, the dust produced by power plants that burn coal, is used as a soil fertilizer.
