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Encyclopedia Britannica - Main :: ORC-PAI |
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OXYGEN (symbol 0, atomic weight 16) , a non-metallic chemical element
element
oxide
chief
oxide
Dingwall
cobalt
cobalt
bright red heat; by the decomposition of hydrogen peroxide by bleaching powder, manganese dioxide, potassium ferricyanide in alkaline solution, or potassium permanganate in acid solution; by heating barium peroxide with an aqueous solution of potassium ferricyanide (G. Kassner, Zeit. angew. Chem., 189o, p. 448) BaO2+2K3Fe(CN)6=Ba[FeK3(CN)s]2+02; by the decomposition of sodium and potassium peroxides with a solution of potassium permanganate in the presence of a trace of nickel salts (G. F. Jaubert, Comptes rendus, 1902, 134, P. 778).Numerous methods have been devised-for the manufacture of oxygen. The more important ate as follows: by decomposing strongly heated sulphuric acid in the presence of a contact substance; by heating an intimate mixture of one part of sodium nitrate with two parts of zinc oxide (T. H. Pepper, Dingler's Jour., 1863, 167, p. 39): 2ZnO+4NaNO3= 2Zn(ONa)2+2N2+502; by the use of cuprous chloride which when mixed with clay and sand, moistened with water and heated in a current of air at 100-200 C. yields an oxychloride, which latter yields oxygen when heated to 400 C (A. Mallet, Comptes rendus, 1867, 64, p. 226; 1868, 66, p. 349); by the electrolysis of solutions of sodium hydroxide, using nickel electrodes; by heating calcium plumbate (obtained from litharge and calcium carbonate) in a current of carbon dioxide (G. Kassner, Monit. Scient., 189o, pp. 503, 614); and from air by the process of Tessie du Motay (Ding. Jour., 1870,196, p. 230), in which air is drawn
Oxygen is a colourless, odourless and tasteless gas. It is somewhat heavier than air, its specific gravity being 1.10523 (A. Leduc, Comptes rendus, 1896, 123, p. 8o5). It is slightly soluble in water and more so in alcohol. It also dissolves quite readily in some molten metals, especially silver. Oxygen does not burn, but is the greatest supporter of combustion known, nearly all the other elements combining with it under suitable conditions (cf. OXIDE). These reactions, however, do not take place if the substances are absolutely dry. Thus H. B. Baker (Proc. Chem. Soc., 1902, 18, p. 40) has shown that perfectly dry oxygen and hydrogen will not combine even at a temperature of loco C. It is the only gas capable of supporting respiration. For the properties of liquid oxygen see LIQUID GASES. It is found, more especially in the case of organic compounds, that if a substance which oxidizes readily at ordinary temperature be mixed with another which is not capable of such oxidation, then both are oxidized simultaneously, the amount of oxygen used being shared equally between them; or in some cases when the substance is spontaneously oxidized an equivalent amount of oxygen is converted into ozone or hydrogen peroxide. This phenomenon was first noticed by C. F. Schonbein (Jour. prakt. Chem., 18581868), who found that on oxidizing lead in the presence of sulphuric acid, the same quantity of oxygen is used to form lead oxide as is converted into hydrogen peroxide. In a similar manner M. Traube (Ber., 18821893) found that when zinc is oxidized in presence of water equivalent quantities of zinc hydroxide and hydrogen peroxide are formed at first, thus: Zn+H2O+02=ZnO+H2O2, followed by ZnO+H2O=Zn(OH)i,Zn+H202=Zn(OH)2. The oxygen uniting with the substance undergoing oxidation is generally known as bound oxygen," whilst that which is transformed into ozone or hydrogen peroxide is usually called " active oxygen." C. Engler (Ber., 1897, 3o, p. 1669) calls the substance which undergoes oxidation the " autoxidizer " and the substance which unites with the active oxygen the " acceptor "; in the oxidation of metals he expresses results as: M+02=MO2, followed by MO2~MO+O, and if water be present, O+H2O = H2O2. Various theories have been developed in order to account for these phenomena. Schonbein (loc. cit.) assumed that the ordinary oxygen molecule is decomposed into two parts which carry electrical charges of opposite kinds, the one with the positive charge being called " antozone " and the other carrying the negative charge being called " ozone," one variety being preferentially used up by the oxidizing compound or element and the other for the secondary reaction. J. H. Van't Hoff (Zeit. phys. Chem., 1895, 16, p. 411) is of the opinion that the oxygen molecule is to a certain extent ionized and that the ions of one kind are preferably used by the oxidizing compound. Traube (loc. cit.), on the other hand, concludes that the oxygen molecule enters into action as a whole and that on the oxidation of metals, hydrogen peroxide and the oxide of the metal are the primary products of the reaction. A. Bach (Comptes rendus, 1897, 124, p. 2) considers that the first stage in the reaction consists in the production of a peroxide whichthen interacts with water to form hydrogen peroxide (see also W. Manchot, Ann., 1901, 314, p. 177; 1902, 325, p. 95). Oxygen is a member of the sixth
the salts of carbonyl compounds the arrangement > C : 0 <1c, whilst J. W. Bruhl and P. W. Walden point out from the physico-chemical standpoint that in water and hydrogen peroxide the oxygen atom is probably quadrivalent. The atomic weight of oxygen is now generally taken as 16, and as such is used as the standard by which the atomic weights of the other elements are determined, owing to the fact that most elements combine with oxygen more readily than with hydrogen (see ELEMENT). Oxygen is widely used in medical practice as well as in surgery. Inhalations of the gas are of service in pneumonia, bronchitis, heart disease, asthma, angina and other conditions accompanied by cyanosis and dyspnoea. They often avert death from asphyxia, or render the end less distressing. Oxygen is also administered in chloroform poisoning, and in threatened death from the inhalation of coal gas or nitrous oxides. It is of value in cyanide and opium poisoning and in the resuscitation of the apparently drowned. The mode of administration is by an inhaler attached to an inhalation bag, which serves to break the force with which the oxygen issues from the cylinders in which it is sold in a compressed form. It can be administered pure or mixed with air as required. If given in too great quantity a temporary condition of apnoea (cessation of breathing) is produced, the blood being fully charged with the gas. Oxygen may be applied locally as a disinfectant to foul and diseased surfaces by the use of the peroxide of hydrogen, which readily parts with its oxygen; a solution of hydrogen peroxide therefore forms a valuable spray in diphtheria, tonsillitis, laryngeal tuberculosis and ozaena. It can also be used with advantage in inoperable uterine cancer, favus and lupus, and as an injection in gonorrhoea and suppurative conditions of the ear. It relieves the pain of wasp and bee stings. Internally hydrogen peroxide is used in various diseased conditions of the gastro-intestinal tract, such as dyspepsia, diarrhoea and enteric fever. The B.P. preparation Liquor Hydrogenii Peroxidi dose z to 2 drs. is synonymous with the Aqua Hydrogenii Dioxidi of the U.S.P. and the ten-volume solution termed eau oxygenee in France. It is customary to use oxygen in combination with chlorofarm, or nitrous oxide in order to produce insensibility to pain (see ANAESTHETICS). End of Article: OXYGEN (symbol 0, atomic weight 16) If you wish, you can link directly to this article.
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