OXAN1LIDK. 



OXYPYROLIC ACID. 



OXANILIDE. [pXAlilDl.] 



OXIDATION. The chemical process of uniting with oxygen ; >ee 



(.'OMBI-STION ; HllKMACAf 818 J OXTUKH. 

 IX1HKS. rOxTQKX.] 



OXYAC'ANTHINE. An organic alkaloid of unknown competition, 

 found along with berberine in the Ucrkeru niliiaru. 



..\ Wt 11 >s. [SMTH.] 



o.XVliKX/olC ACID (C..H.OA An organic add isomerio with 

 salicylic acid. It U obtained by the prolonged action of nitrous acid 

 upon benxamio acid. It U a colourless, orystalUsable acid, forming 

 salts which are termed ojeyhmnata. 



OXYl'HLoltlliKS. Chemical compounds containing both chlorine 

 and oxygen united with some other element or radical. Thus oxy- 

 chloride of phosphorus PCl.,11,. 



OXYCOBALTIA. One of the ammoniacal compounds of cobalt. 

 [COBALT. Awwumiatal compound! of cobalt.] 



OXYGEN (0), an elementary body, the properties of which are best 

 known and most remarkable in its elastic or aeriform state, in which it 

 is termed vsyge* go*. The most important discovery of this substance 

 was made by Dr. Priestley, on the 1st of August, 1774; and of his 

 numerous contributions to chemical science, this is at once the most 

 splendid and the moat solid, and has rendered his name imperishable. 



Dr. Priestley has stated, with his usual candour, that the discovery 

 was also made, quite independently, though later, by Scheele, and he 

 has refuted the unjust claim of Lavoisier to be also one of the dis- 

 coverers of this element. To this gas Dr. Priestley gave the name of 

 ile/'ltl"<jit<icaUfl air, Scheele called it empyreal air, and Condorcet rital 

 air. Lavoisier gave it the name of oxygen, from the Greek words t^us, 

 acid, and the root yn, to generate, because he considered it as the sole 

 cause of acidity ; this appellation it still retains, although it is now well 

 known that there are acids which do not contain it and alkalies 

 which do. 



Dr. Priestley first prepared this gaseous body by heating the binoxide 

 of mercury, then called mercuriiu prrrcipittttut per te, in an air- jar, over 

 mercury, by means of a lens, and he afterwards obtained it from other 

 substances. 



It is now prepared in various ways, according to the purposes to 

 which it is intended to be applied. These ways we shall briefly state 

 and explain, and also describe the production of the gas from the bin- 

 oxide of mercury, first used by Dr. Priestley. 



When mercury is heated, and at the same time exposed to atmos- 

 pheric air, it is found that the volume of the air is diminished, and the 

 weight of the mercury increased, and that it becomes, during the 

 operation, a red crystalline body, which is the binoxide of mercury, 

 formed by the metal combining with the oxygen of the air. 



When this substance is subjected in a retort to a higher temperature 

 than that required for its formation, the affinity between the metal and 

 the oxygen is overcome ; the former returns to its metallic state, and 

 the latter to its gaseous form ; and if added to the residual atmospheric 

 air, its volume is restored. 



If it be quite pure, and the operation be accurately performed, 216 

 grains (1 equivalent) of binoxide of mercury should be separated by the 

 agency of heat into 200 grains, one equivalent of mercury, and 16 grains, 

 two equivalents of oxygen, measuring 46'7 cubic inches. 



By this process then oxygen gas is, though indirectly, obtained from 

 atmospheric air : but there is a natural metallic oxide, the binoxide of 

 vuHujatute, which is found plentifully, and which also yields it by the 

 mere application of heat, and the quantity of gas obtained is dependent 

 upon the degree of heat employed ; in this case, however, unlike that 

 of the binoxide of mercury, the metal is not reduced. The equivalent 

 of binoxide of manganese [MANGANESE] is 43-57, consisting of 27-57 of 

 metal and 2 equivalents of oxygen =16; and when 43-57 groins are 

 heated to moderate redness in a coated glass retort, half an equivalent 

 of oxygen, or 4 grains, measuring 11 1>7 cubic inches, are expelled, and 

 there remains in the retort an equivalent of sesquioxide of manganese, 

 composed of 27'57 metal and 12 oxygen = 39'57. But if the equivalent 

 of binoxide be strongly heated in an iron retort, it is then converted 

 into red oxide, consisting of one equivalent of metal, and one and 

 one-third of oxygen, while two-thirds of an equivalent of oxygen are 

 expelled, weighing 5'33 grains and measuring 15'56 cubic inches. 



Another but less eligible method of obtaining oxygen from the bin- 

 oxide of manganese, is to heat it with sulphuric acid in a retort ; in 

 this cue an equivalent of the binoxide = 43-57, loses a whole equivalent 

 of oxygen = 8 grains, or 23-35 cubic inches, and there remain in the 

 retort protoxide of manganese combined with the sulphuric acid, 

 forming protosulphate of manganese. It is to be observed that these 

 statements of the quantities of oxygen procurable from a given quantity 

 of the binoxide of manganese are made on the supposition of its being 

 quite pure, which is hardly ever the case ; the binoxide of commerce 

 very commonly contains 20 per cent, of impurity. 



Red oxide and binoxide of lead also, when heated, either with or 

 without sulphuric acid, yield oxygen gas, but the quantity obtained is 

 small, and the processes are on several account* ineligible. When 

 nitrate of potash also U heated to redness, it give* out a considerable 

 quantity of oxygen gas, from the decomposition of the nitric acid ; but 

 as it comei over mixed at different periods of the operation with 

 variable quantities of the nitrogen gas of the nitric acid, this is not a 

 method usually resorted to. 



The oxygen gas obtained from binoxide of manganese is su.Iicieiitly 

 }>ure for all the usual purposes of experiment* intended m.-i 

 illustrate the properties of the gas; but when the gas is required 

 for chemical analysis or accurate investigations, it is then obtained from 

 the salt formerly called oxyinuriate of potash, but now chlorate of 

 poUth. 



Chlorate of potash is com-Kwed of one equivalent of chloric acid 

 75-45, and one of potash 47 = 122'45; and when heated in a retort, 

 is resolved into an equivalent of chloride of potassium 74-46, which 

 remains in the retort, and 6 equivalents of oxygen, 5 from the acid and 

 1 from the potash = 48, which measure 140 cubic inches ; so that 

 is scarcely any other substance which yields so much oxygen gas or of 

 so great purity. 



The evolution of the oxygon is greatly facilitated by mixing with 

 the chlorate of potash about one-sixth of its weight either of binoxide 

 of manganese or oxide of copper, and the process thus modified is now 

 almost exclusively used for the preparation of oxygen gas. 



Oxygen possesses great power of combination with other elementary 

 bodies, there being only one (fluorine) with which it is not known to 

 combine, either by direct union or indirect chemical action. The com- 

 pounds to which it gives rise by combining with certain metals, and 

 ;il -i indeed with some other bodies, may be classed under the three 

 heads of oxides, acids, and alkalies. There are many bodies which, by 

 a moderate degree of oxidation, become first oxides, and by an increased 

 degree, acids; such substances are charcoal, phosphorus, chromium, 

 &c. : but there is no instance of its forming with different proportions 

 of the same element an acid and on alkali. 



The properties of oxygen gas are, that it is devoid of colour, taste, 

 or smell, and being transparent, it is also invisible. It possesses the 

 mechanical properties of common air ; it is capable of being respired, 

 and a given volume of it will support lifu much longer than an equal 

 bulk of common air ; on this account the name of vital air was bestowed 

 upon it. It is heavier than atmospheric air, 100 cubic inches at a 

 medium temperature and pressure weighing 84'20S grains, whereas an 

 equal vultime of atmospheric air weighs 31*074 grams. It is but slightly 

 soluble in water, requiring about 20 times its bulk for solui 

 has no effect upon this gas ; by heat, like-all gaseous bodies, it is merely 

 expanded ; and electricity is incapable of effecting any change in its 

 properties. Oxygen gas has not been rendered either liquid or solid by 

 the united agency of cold and pressure, and not having been divided 

 into two or more kinds of matter, it is considered as elementary in ita 

 nature. Its equivalent, atomic or combining weight, is 8. 



It will be proper here to notice the production of oxygen gas by the 

 action of electricity, especially voltaic electricity, which, as is well 

 known, possesses uie power of evolving both oxygen and hydrogen 

 from water. Oxygen gas is also evolved by the action of the sun's rays 

 on the moistened leaves of trees, which by this agency decompose the 

 carbonic acid diffused in the atmosphere from various sources, and by 

 combining it with their carbon, flourish and increase in H, < When 

 compounds containing oxygen are decomposed by voltaic electricity, 

 the oxygen is evolved in the gaseous state at the anode or positive 

 pole. 



The most remarkable property of oxygen gas, and that on account of 

 which it was once called fin-air, is the facility and splendour with 

 which bodies, when previously ignited, burn in it. Substances which 

 do not undergo combustion in the air, will readily do so, and with great 

 brilliancy, in oxygen gas ; iron for example burns very readily in it 

 when previously made red-hot. The intensity of the light emitted by 

 burning phosphorus in oxygen gas is such as to be scarcely tolerable. 



In conclusion, we may remark, that until after the discovrrv of this 

 gas nothing was or could be known respecting the nature of the air, ot 

 water, or of earth, all of which, formerly reckoned as elementary 1 

 are now known to be compound, and to contain oxygen as one of their 

 constituents. It has also thrown great and unexpected light on the 

 nature of combustion and respiration. 



The compounds which oxygen forms with metals and other elementary 

 bodies, are treated of in the respective articles on those elements, 

 whether they are oxides, acids, or alkalies. The importance of the 

 oxygen of the AIR as affecting RESPIRATION, VEGETATION, COMBUSTION, 

 and KRE1IACAU8I8, is fully enlarged upon under those words. 



DXYGKNATKl) \VATKIt. ; II 



OXYHYWIOGEN BLOWPIPE. A jet of flame of very hL-h 

 temperature, produced by the combustion of mixed hydrogen 

 i icases, as described under DRUMMOND LIMIT. 



uXYI.I/.AKIC ACID. Synonymous with purpurin. [MADDER, 

 mitten of.] 



nXYMUUATIC ACID. [CHLORINE.] 



dXY 'Ai'HTHAI.IC ACID. [NAPUTHAI.TO GROUP.] 



( > X Y I ' 1 1 K N 1 1 ' A < ' 1 1 1 (C H.OJ . Binoxide of Pheyl ; Pyrocatt- 



\nt(. A colourless crystalline bo.1 



by distilling catechu or inorintannic acid. It is also contained in wood 

 vinegar. 



uXYPIciHC ACID. [PHENYLIO GROUP.] 



iiXYI'i-KPHYRIC ACID. [EuxANrmo Aero.] 



OXYI'KOTKIN. [PROTEIN.] 



OXYI'YKMI.IC At 111 J,.H It O, ?). An organic acid, formed 

 simultaneously with succinic acid when nitric acid acts upon sebacic 

 acid. 



