Phlogiston - ever heard of it? Per phlogiston theory, in all flammable materials there is present phlogiston, a substance without color, odor, taste, or weight that is given off in burning. 'Phlogisticated' substances are those that contain phlogiston and, on being burned, are 'dephlogisticated.' The ash of the burned material is held to be the true material. The theory received wide support throughout a large part of the 18th century until it was refuted by the work of A. L. Lavoisier, who revealed the true nature of combustion. Seems the theory has been dephlogisticated.