In physics and chemical engineering, the term Pouillet effect refers to an exothermic reaction that takes place when a liquid is added to a powder. Strictly speaking, the heat generated is caused by adhesion of the liquid to the surface of the particles rather than by a chemical reaction.[1] It was first observed in 1802 by physicist John Leslie, who noted that heat was evolved when dry sawdust was wetted with water.[2]Claude Pouillet later described this phenomenon in 1822, and it subsequently became known as the Pouillet effect in France, and then elsewhere.[3][4]
^Taggart, Arthur F.; Beach, Frederick E. (November 1, 1916). "An Explanation of the Flotation Process". Metallurgical and Chemical Engineering. 15 (9): 518–523. Retrieved 19 February 2022.
^Leslie, John (1802). "On capillary action". Philosophical Magazine. 1st series. 14 (55): 193–205. doi:10.1080/14786440208676183. From p. 201: Upon wetting paper or linen with water or oil, and " … applying a delicate thermometer, I perceived a very sensible extrication of heat invariably to take place during such combinations. And this effect was the greater in proportion to the previous dryness of the solid. Thus I have sometimes produced a heat of ten degrees by moistening saw-dust which had been parched before the fire."
^Pouillet (1822). "Mémoire sur de nouveaux phénomènes de production de chaleur" [Memoir on new phenomena of heat production]. Annales de Chimie et de Physique. 2nd series (in French). 20: 141–162. From p. 142: "À l'instant où un liquide mouille un solide, il y a dégagement de chaleur."
(At the instant when a liquid wets a solid, there is a release of heat.)
^'Adsorption by powders & porous solids: principles, methodology and applications' Academic Press, 1999.