Abstract: Formation of dioxins in flue gases is inhibited by contacting the flue gas with at least one of sodium phosphite, calcium phosphate, sodium hypophosphite, and calcium as reducing agents preferably at a temperature in the range of from 150° C. to 850° C. Hydrogen chlorides are also rendered harmless by the contact with the reducing agent. Also, metal ions contained in the fly ash of the flue gas are reduced to metals to reduce the occurrence of dissolution of the metals in subsequent treatment of the fly ash.

Abstract: Disclosed herein are a solid waste treatment agent comprising phosphorous acid or a derivative thereof and/or hypophosphorous acid or a derivative thereof, or phosphorous acid or a derivative thereof and/or hypophosphorous acid or a derivative thereof, and an aluminum compound and/or a titanium compound, and a method of treating solid waste, which comprises adding the solid waste treatment agent to solid waste containing harmful metals and/or organic chlorinated compounds such as dioxins and PCB to make the solid waste harmless.

Abstract: A thermally reversible color forming composition which includes an electron-donating chromophoric compound and an electron-accepting compound, by which formation and deletion of a color image may be carried out by adjusting thermal energy applied to the composition, wherein the electron-accepting compound is a carboxylic acid compound having the following general formula (1):R.sub.1 --X--R.sub.2 --COOH (1)in which, X represents a divalent group having at least one hetero atom, R.sub.1 represents a hydrocarbon group having at least one hetero atom, R.sub.2 represents an aliphatic hydrocarbon group, which may be substituted and whose principle chain contains less than 6 carbon atoms.