(Encyclopedia) hydrofluorocarbons: see under chlorofluorocarbons. (Encyclopedia) hydrofoil, flat or curved finlike device, attached by struts to the hull of a watercraft, that lifts the moving watercraft above the water's surface. The term is often extended to? (Encyclopedia) hydrogen h?dr?j?n [Gr.,=water forming], gaseous chemical element; symbol H; at. no. 1; interval in which at. wt. ranges 1.00784?1.00811; m.p. ?259.14°C;; b.p. ?252.87°C? (Encyclopedia) hydrogenation h?drj?n??sh?n, h??dr?j?n?sh?n, chemical reaction of a substance with molecular hydrogen, usually in the presence of a catalyst. A common hydrogenation is the hardening? (Encyclopedia) hydrogen bomb or H-bomb, weapon deriving a large portion of its energy from the nuclear fusion of hydrogen isotopes. In an atomic bomb, uranium or plutonium is split into lighter? (Encyclopedia) hydrogen chloride, chemical compound, HCl, a colorless, poisonous gas with an unpleasant, acrid odor. It is very soluble in water and readily soluble in alcohol and ether. It fumes in? (Encyclopedia) hydrogen cyanide, HCN, colorless, volatile, and extremely poisonous chemical compound whose vapors have a bitter almond odor. It melts at ?14°C; and boils at 26°C;. It is? (Encyclopedia) hydrogen fluoride, chemical compound, HF, a colorless, fuming liquid or colorless gas that boils at 19.54°C;. It is miscible with water and is soluble in benzene, toluene, and? (Encyclopedia) hydrogen-ion concentration: see pH. (Encyclopedia) hydrogen peroxide, chemical compound, H2O2, a colorless, syrupy liquid that is a strong oxidizing agent and, in water solution, a weak acid. It is miscible with cold water and is?