OXA 



OXI 



quescent in moist air ; and cold water 

 dissolves about one-half its weight of the 

 acid : boiling water dissolves a quantky 

 equal to its own weight. This acid is de- 

 composed by the sulphuric acid with heat, 

 and charcoal is deposited : at the boiling 

 temperature it is decomposed by the nitric 

 acid, and converted into water and car- 

 bonic acid : its component parts are 



Oxygen 77 



Carbon 13 



Hydrogen 10 



100 



It combines with alkalies, earths, and 

 metallic oxides, and the salts thus formed 

 are denominated oxalates. The great at- 

 traction which this acid has for lime ren- 

 ders it of great utility in detecting that 

 substance in every soluble combination. 



OXALATES, in chemistry, salts form- 

 ed of the oxalic acid and certain bases, 

 are distinguished by the following pro- 

 perties : when exposed to a red heat, the 

 acid is decomposed and driven off, and 

 the base only remains. Lime water pre- 

 cipitates a white powder from their so- 

 lutions, provided no excess of acid be pre- 

 sent : the earthy oxalates are, in general, 

 nearly insoluble in water, but they may 

 be rendered soluble by an excess of the 

 more powerful acids. See OXALIC acid. 



OXALIS, in botany, wood-sorrel, a ge- 

 nus of the Decandria Pentagynia class 

 and order. Natural order of Gruinales. 

 Gerania, Jussieu. Essential character : 

 calyx five parted ; petals five, often con- 

 nected at the base ; capsule five-celled, 

 five-cornered, opening at the corners; 

 seeds arilled. There are ninety-six spe- 

 cies, of which the O. acetosella, common 

 wood-sorrel, has a perennial, branched, 

 knobbed, creeping root, having fine fi- 

 brils on every side, partly red and partly 

 white, with an ovate, acute, rigid scale, 

 like a tooth, at the knobs ; scapes one or 

 two, jointed at the base, the length of the 

 leaves ; calycine leaflets, oblong, acute, 

 sometimes bifid, ciliate, purple at the tip, 

 upright. Linnaeus remarks, that the leaf- 

 lets in wet weather are erected, but hang 

 down in dry weather. It has been observ- 

 ed, that this elegant little plant has the 

 leaves of trefoil, the taste of sorrel, and 

 the flower of geranium ; from which 

 last genus this is distinct, in the num- 

 ber of styles, the form of the capsule and 

 manner of its opening, its straight corcle, 



or heart, without any perisperm or albu- 

 men : it is common all over Europe. 



OXGANG, or OXGATE, is generally 

 taken, in our old law books, for fifteen 

 acres, or as much ground as a single ox 

 can plow in a year. 



OXIDE, in 'chemistry. Metallic sub- 

 stances are not only of vast importance in 

 the arts of civilized life, on account of the 

 properties which belong to them in the 

 metallic state ; but many of them are not 

 less valuable in those changes which 

 they undergo by new combinations, and 

 the new properties they acquire, in con- 

 sequence of these changes. One of the 

 first and most ordinary changes to which 

 metallic substances are subject, is their 

 combination with oxygen. This is called, 

 in chemical language, oxydation. If a 

 metal, as for instance, a piece of iron, is 

 exposed to the air, when it is moist, it 

 soon undergoes a remarkable change. 

 It loses its metallic lustre, and the surface 

 is covered with a brownish powder, well 

 known by the name of rust. This 

 change is owing to the combination of 

 oxygen with the metal, and the rust of 

 the metal in this state is known in che- 

 mistry by the name of oxide. The pro- 

 cess by which this compound of oxygen 

 and a metallic substance is formed, is 

 called oxydation, and the product is de- 

 nominated an oxide. The process of oxy- 

 dation is effected more rapidly when 

 metals are exposed to the action of heat ; 

 and, indeed, many metals require a very 

 high temperature to produce the combina- 

 tion, while it cannot be accomplished in 

 others by the greatest degree of heat that 

 can be produced. This process was for- 

 merly called calcination, or calcining the 

 rm.tal ; and the product now denominated 

 an oxide, was distinguished by the name 

 of calx or calces, from its being reduced 

 to the state of powder, in the same way 

 as limestone, by burning. Metals differ 

 very much from each other in the cir- 

 cumstances in which this oxydation takes 

 place, as in the temperature which is 

 necessary, the facility of the combination, 

 the proportions of oxygen which combine, 

 and the force of afiinity between the con- 

 stituent parts of the oxide. Some metals 

 are oxydated in the lowest temperature, 

 as, for instance, iron and manganese ; 

 while others require the greatest degree 

 of heat that can be applied Such are 

 silver, gold, and platina. 



The facility with which oxydation takes 

 place in some metals is so great, such as 

 in iron, tin, lead, copper, and manganese, 

 that they must be completely defended 



