64 



CHEMISTRY. 



metal— of a fibrous texture—sp. gr. 9*7— is very infusible— suscep- 

 tible of the welding process— is attracted by the magnet— may itself 

 be rendered magnetic by heating— does not oxidize in dry air at com- 

 mon temperatures ; — heated to redness, it becomes covered with a 

 scaly coating of the black oxide — burns vividly in oxygen— rusts 

 when exposed to air and moisture — decomposes water at a red heat, 

 evolving pure hydrogen, and giving rise to the black oxide. Symb. 

 (Ferrum,) Fe. — Eq. 28. — It forms four compounds with oxygen. 



Protoxide, FeO,— the base of the native carbonate and of green 

 vitriol. It can hardly be isolated, from its great proneness to absorb 

 oxygen, and to pass into the state of sesquioxide ; the hydrate of the 

 protoxide is formed when an alkali is added to a solution of thepro- 

 tosulphate; it is of a dirty green colour, and speedily becomes red 

 by the absorption of oxygen. 



Peroxide, ( Sesquioxide) FePg, — occurs in nature under the name 

 o{ red hematite; — made by dissolving iron in nitro-hydrochloric acid, 

 and adding an alkali. Prop. — It is not attracted by the magnet ; — 

 forms reddish salts with most of the acids. It can easily be detected 

 by the infusion of galls, which gives with it a bluish-black precipi- 

 tate, the basis of ink, — by ferrocyanide of potassium, which throws 

 ^owxi Prussian blue,— hy sulphocyanide of potassium, which causes 

 a blood-red colour. 



Black, or Magnetic Oxide, FeO-f FePg,— a mixture of the two 

 former oxides ; — occurs native — is one of the most valuable of the 

 ores ; it is the product of exposing iron to high heat. It does not 

 form salts. 



Ferric Acid, FeOg, — only recently discovered — obtained by heat- 

 ing together one part of peroxide of iron with four parts of dry nitre, 

 by which \\\q ferrate of potash is found ; it is very difficult to isolate, 

 on account of its extreme susceptibility to decomposition. 

 Iron forms two compounds with chlorine. 



Protochioride FeCl, — formed by dissolving iron in chlorohydric 

 acid and drying. 



Sesquichloride, Fe^Clg, formed by the combustion of iron wire in 

 chlorine gas. There are also two iodides ; the protiodide is used in 

 medicine, made by digesting iodine in water with pure iron wire. 

 Sulphur unites with iron in several proportions. 

 Protosulphuret, FeS, — formed by heating iron and sulphur together; 

 it has a blackish colour, — is attracted by the magnet. There is also a 

 Sesquisulpjhuret, Fe^Sg. 



Bisulphuret, FeS^, iron pyrites, exists native, has a yellow colour 

 and a metallic lustre ; is not magnetic. 



Magnetic iron pyrites, is a native ore, consisting of a compound 

 of the protosulphide and bisulphide (Stromeyer). 



The most important salts of iron are the sulphates, the carbonate, 

 and the nitrate. 



