kuijianb

224. When iron is exposed to the combined action of air and moisture, it absorbs oxygen at common temperatures.
Illus. The comon rust of iron is an oxide of that metal.
225. Iron combines with the acids, and forms conn pounds of various kinds.
Obs. Among these, the sulphate of iron, called also green vitriol or copperas, is the most important.
226. When sulphate of iron is mixed with an infusion of galls, we obtain a black solution, which is a new compound of oxide of iron with the gallic acid and tan.
Illus. Wriiing ink is a gallale of iron, made with tincture of galls, and sulphate of iron.
Obs. The black colour of ink is owing to its combination with oxygen.
Illus. The addition of iron filings to ink destroys its colour by absorbing its oxygen. Characters written with ink after this treatment, are at first illegible, but become black as the iron acquires oxygen from the air. Writing with ink newly made is well known to grow more intensely black by expoture to the air; this is on the same principle.
227. Ink is decomposed by alkalies, by acids, and by age. In some instances its colour may be restored by adding the ingredient which is lost.
Illus. 1. The alkalies, as potash, or soda, will destroy the colour of writing; but the colour may be restored by moistening the paper with infusion of galls on a camels hair pencil.
2. Ink is decomposed by age, partly in consequence of the farther oxidation of the iron, and partly in consequence of the destruction of the gallic acid. Hence ink stains degenerate into iron-moulds, and these last are immediately produced on an inked spot of linen when washed with soap, because the alkali of the soap abstracts the gallic acid, and leaves only an oxide of iron. Hence also the yellowish colour which is produced by dipping linen into a solution of sulphate of iron and called a copperas colour, is only a precipitation of the oxide of iron on the cloth.
227. Iron combines with carbon in various proportions.
Obs. 1. Steel is a compound of iron and carbon ; the iron absorbs the carbon from the charcoal with which it is heated.
2. Cast, or crude iron, contains oxygen and carbon. When these are got rid of by the process of refining, malleable or bar iron is formed, tron however, always contains more or less oxygen and carbon.

Coach poppy collection,Gucci high top shoes .Louis Vuitton Travel Bags