O X A
O X Y
( 194 )
This acid diffolves magnefia, and forms awhite powder which is infoluble in water oralcohol unlefs the acid be fuperabundant. i ooparts of the fait are eftimated by Bergman tocontain 35 of magnefia.
Oxalat of Alumine.
Oxalic acid digefted on clay, diffolves thealumine, and forms an uncryftallizable mafs ofa fweetifh aftringent tafte: 100 parts contain44 of alumine.
Metallic Oxalats. -
A few only of thefe require particular notice.
Oxalat of Silver . When oxalic acid or an alka-line oxalat is added to nitrated filver in folution,a white infoluble oxalat of filver is produced.Sulphat of filver is equally precipitated by thisacid. Oxalat of filver is fpeedily blackened bythe fun’s rays, and in part decompofed. Inthis ftate if heated to rednefs it difperfes with afudden noife.
Oxalat of Mercury is formed by adding thisacid to any folution of the metal. It is awhite infoluble powder, but blackens in thefun’s rays.
Oxalat of Lead . Lead is corroded by thisacid, and its oxyd is readily diffolved, andcryftallizes by evaporation. The oxalic aciddecompofes the nitrat and acetite of lead, butnot the fulphat, and hence in Scheele ’s originalexperiments the fulphuric acid was ufed todifengage the oxalic acid from the oxalat oflead formed by adding the fait of forrel to theacetite of this metal.
Oxalat of Copper . This acid diffolves copperboth metallic and oxidated. The fait is fcarcelyfoluble in water. Moll of the other folutionsof this metal are decompofed by the oxalicacid, and an infoluble oxalat falls down.
Oxalat of Iron. Iron is readily diffolved bythis acid with copious difengagement of hydro-gen gas. This folution gives by concentrationgreenifh yellow prifmatic cryftals, eafily folublein water. It alfo diffolves many of the fallsand oxyds of this metal, and hence its originalufe in removing iron-mould fpots in linen.When added to the red fulphat or muriat ofthis metal, a fine red oxalat of iron is precipi-tated, foluble in an excefs of the fame acid.
Moll of the other metals (gold and platinaexcepted) are foluble in this acid, forming faltsgenerally of little folubility except with anexcefs of acid.
The fuper-oxalat of potalh alfo a£ls uponiron, copper, and feveral other metals, and
thefe folutions retain the potalh belonging tothe acidulum, and cryftallize with it into triplefalts that deferve further examination.
OXYD.
This term may be properly applied to anyfubftance chemically combined with oxygen,but it is rellritled to thofe that have not ac-quired acid properties by the combination. Itis chiefly ufed to exprefs thofe modifications ofmetallic bodies formerly termed calces.
OXYGEN GAS. Dephlogifticated air (ofDr. Prieftley.) Vital air. Empyreal air (ofScheele .) Der Sauerf offe. Germ.
Oxygen is probably the moll abundant of allnatural bodies, and its chemical properties arefo important that a very large lhare of thefcience of chemiftry confilts in a knowledge ofthe combinations and agency of this body.
There are two immenfe fources whenceoxygen is derived, namely water and air. Inthe former it is condenfed into the liquid form,and combined with about a third of its weightof hydrogen: in the latter it is united withazot, and forms little more than a fifth of theatmofphere.
There are befides other fmaller fources ofoxygen, fuch as many parts of the organizedworld, vegetable or animal, (independent ofthe water which they contain fo abundantly,)mineral acids, and metallic oxyds, &c. but thequantity from thefe latter fources is extremelyfmall in comparifon with the former.
Oxygen when free from all combinations,(that of light and heat excepted) is in thegafleous form, and it was firlt obtained byDr. Prieftley in the year 1774 from the oxydof mercury, and the year following it was dif-covered by Scheele , who procured it from theoxyd of manganefe.
We fhall not purfue the hiftory of the dif-coveries relating to this important fubftance,but proceed with its properties as now fullyafcertained, and the modes of procuring it.
The pureft poffible oxygen gas is obtainedby diftilling per fe the dry oxymuriat of potafh.This fait is to be put into a fmall glafs retort,and with the heat of an Argand’s lamp itmelts, and then is decompofed, giving out anabundance of oxygen gas of great purity, whichis to be received over water or mercury in theufual way. When the heat is railed to rednefs,all the oxygen is expelled, and in this way100 grains of the fait will afford about 112cubic inches' 1 of oxygen of extreme purity.This method however is expenfive, but oxygen
* Chenevix,