IRON. 169 



hydroxide are formed ; the two substances are not separated from each other, 

 the mixture being intended for immediate administration as an antidote in 

 cases of arsenic poisoning. 



Ferrous-ferric oxide, PeO.Pe 2 O 3 (Magnetic oxide). This com- 

 pound, which shows strong magnetic properties, has been mentioned 

 above as one of the iron ores, and is known as loadstone. It has a 

 metallic lustre and iron-black color, and is produced artificially by 

 the combustion of iron in oxygen, or in the hydrated state by the 

 addition of ammonium hydroxide to a mixture of solutions of ferrous 

 and ferric salts. 



Iron trioxide, PeO 3 . Not known in a separate state, but in com- 

 bination with alkalies. In these compounds, called ferrates, FeO 3 

 acts as an acid oxide, analogous to chromium trioxide, CrO 3 , in chro- 

 mates. The composition of potassium ferrate is K 2 FeO 4 . 



Ferrous Chloride, FeCl 2 (Protochloride of iron), is obtained as a 

 pale-green solution by dissolving iron in hydrochloric acid : 

 Fe + 2HC1 = FeCl 2 + 2H. 



By evaporation of the solution, the dry salt may be obtained. The 

 solution and salt absorb oxygen very readily : 



3FeCl 2 -f O = FeO + Fe 2 CI 6 . 

 Ferric chloride, ferrous, and afterward ferric oxide, are formed. 



Ferric chloride, Ferri chloridum, Fe 2 Cl 6 .12H 2 O = 54O.2 (Chlo- 

 ride, sesqui-chloride, or perchloride of iron), is obtained by adding to 

 the solution of ferrous chloride (obtained as mentioned above) hydro- 

 chloric and nitric acids in sufficient quantities, and applying heat 

 until complete oxidation has taken place. The nitric acid oxidizes 

 the hydrogen of the hydrochloric acid to water, while the chlorine 

 combines with the ferrous chloride, nitrogen dioxide being formed 



also: 



6FeCl 2 + 2HN0 3 + 6HC1 = 3Fe 2 Cl 6 + 4H 2 O -f 2NO. 



By sufficient evaporation of the solution, ferric chloride is obtained 

 as a crystalline mass of an orange-yellow color; it is very deli- 

 quescent, has an acid reaction, and a strongly styptic taste. The 

 water of crystallization cannot be expelled by heat, because heat 

 decomposes the salt, free hydrochloric acid and ferric - oxide being 

 formed. 



Experiment 26. Dissolve by the aid of heat 1 gramme of fine iron wire in 

 about 4 c.c. of hydrochloric acid, previously diluted with 2 c.c. of water* 



