hydrogen
(H) [hi´dro-jen] a chemical element, atomic number 1, atomic weight 1.00797. (See Appendix 6.) It exists as the mass 1 isotope (protium, or light or ordinary hydrogen), mass 2 isotope (deuterium, heavy hydrogen), and mass 3 isotope (tritium).
hydrogen cyanide an extremely poisonous colorless liquid or gas, HCN, a decomposition product of various naturally occurring glycosides and a common cause of
cyanide poisoning. Inhalation of the gas can cause death within a minute. Called also
hydrocyanic acid.
hydrogen ion concentration the degree of concentration of hydrogen ions (the acid element) in a solution. Its symbol is pH, and it expresses the degree to which a solution is acidic or alkaline. The pH range extends from 0 to 14, pH 7 being neutral, a pH of less than 7 indicating acidity, and one above 7 indicating alkalinity. See also
acid-base balance.
hydrogen peroxide H2O2, an antiseptic with a mildly antibacterial action. A 3 per cent solution foams on touching skin or mucous membrane and appears to have a mechanical cleansing action.
hydrogen sulfide H2S, a poisonous gas with an offensive smell, released from decaying organic material, natural gas, petroleum, and sulfur deposits, and sometimes used as a chemical reagent.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.