IRON. 



iron, at the same time that a large quan- 

 tity of hydrogen is disengaged, and the 

 mixture becomes hot. In this, as well as 

 in the sulphuric solution of iron, the same 

 quantity of alkali is said to be required 

 to saturate the acid as before the solution ; 

 whence it is inferred, that the acid is not 

 decomposed, but that the oxidation is ef- 

 fected by the oxygen of the water ; 

 whence also it appears to follow, that the 

 hydrogen must be afforded from the de- 

 composed water, and not from the metal. 

 Carbonic acid, dissolved in water, com- 

 bines with a considerable quantity of iron, 

 in proportion to its mass. Vinegar scarce- 

 ly dissolves it, unless by the assistance of 

 the air. 



Phosphoric acid unites with iron, but 

 very slowly. The union is best effected 

 by adding an alkaline phosphate to a so- 

 lution of one of the salts of iron, when it 

 will fall down in a white precipitate. A 

 saturated phosphate of iron has been 

 found native in France, semi-transparent, 

 of a red brown colour, and foliated tex- 

 ture. A deep blue phosphate of iron, 

 lamellated, and fragile, of the specific 

 gravity of 2.6, brought from the Isle of 

 France, and analysed by Laugier, Four- 

 croy, and Vauquelin, gave iron 41.25, 

 phosphoric acid 19.25, water 31.25, alu- 

 mina, 5, and ferruginous silex 1.25, in 100 

 parts. A similar phosphate has been 

 found in Brazil. This acid is found com- 

 bined with iron in the bog ores, and, 

 being at first taken for a peculiar metal, 

 was called siderite by Bergman. 



Liquid fluoric acid attacks iron with 

 violence ; the solution is not crystalliza- 

 ble, but thickens to a jelly, which maybe 

 rendered solid by continuing the heat. 

 The acid may be expelled by heating it 

 strongly, leaving a fine red oxide. 



Borate of iron may be obtained by pre- 

 cipitating a solution of the sulphate with 

 neutral borate of soda. 



Arsenic acid likewise unites with iron. 

 This arseniate is found native in Corn- 

 wall, in pretty large cubic crystals, toler- 

 ably transparent, of a dark green colour, 

 with a brownish tinge ; sometimes yel- 

 lowish, or of a brown yellow, like resin. 

 The Count de Bournon found likewise ai 

 cupreous arseniate of iron, in minute 

 rhomboidal crystals, of a faint sky blue 

 colour and uncommon brilliancy. Speci- 

 fic gravity 3.4. The green and red sul- 

 phates of iron may be decomposed by 

 arseniate of ammonia, and afford arseniate 

 of iron in the two different states. 



Chromate of iron is said to have been 

 found abundantly in the department of 

 Var in France, and to form a beautiful 



green for enamelling or colouring pastes. 

 Its analysis by Vauquelin and Tassaert 

 gave chromic acid 43, oxide of iron 34.7, 

 alumina 20.3, silex 2, in 100 parts. 



In the dry way, this metal does not 

 combine with earths, unless it be pre- 

 viously oxided ; in which case it assists 

 their fusion, and imparts a green colour 

 to the glass. It apprears to combine with 

 alkalies by fusion. Nitre detonates strong- 

 ly with it, and becomes alkalized. 



Sulphur combines very readily with 

 iron in the dry, and even in the humid 

 way, though neither of these substances 

 is scarcely at all soluble in water. A 

 mixture of iron filings and flowers of sul- 

 phur being moistened, or made into a 

 paste, with water, becomes hot, swells, 

 adheres together, breaks, and emits 

 watery vapours of an hepatic smell If 

 the mixture be considerable in quantity, 

 as for example, one hundred pounds, it 

 takes fire in twenty or thirty hours, as 

 soon as the aqueous vapours cease. 



By fusion with iron, sulphur produces 

 a compound of the same nature as the 

 pyrites, and exhibiting the same radiated 

 structure when broken. If a bar of iron 

 be heated to whiteness, and then touched 

 with a roll of sulphur, the two substances 

 combine, and drop down together in a 

 fluid state. It is necessary that this ex- 

 periment should be made in a place 

 where there is a current of air to carry 

 off the fumes ; and the melted matter, 

 which may be received in a vessel of 

 water, is of the same nature as that pro- 

 duced by fusion in the common way, ex- 

 cepting that a greater quantity of sulphur 

 is fused by the contact of the bar of iron. 

 According to Proust, the native sulphuret, 

 or pyrites, contains 47.36 per cent, of 

 sulphur, the artificial sulphuret but 37.5. 

 Mr. Hatchett however has found, that 

 the magnetical pyrites contains the same 

 proportion as the artificial sulphuret. 



Phosphorus may be combined with 

 iron, by adding it cut into small pieces to 

 fine iron wire, heated moderately red ia 

 a crucible ; or by fusing six parts of iron 

 clippings, with six of glacial phosphoric 

 acid, and one of charcoal powder. This 

 phosphuretis magnetic; and Mr. Hatchett 

 remarks that iron, which in its soft or 

 pure state cannot retain magnetism, is 

 enabled to do so, when hardened by car- 

 bon, sulphur, or phosphorus, unless the 

 dose be so great as to destroy the mag- 

 netic property, as in most of the natural 

 pyrites and plumbago. 



The combination of carbon with iron 

 is of all the most important, under the 

 names of cast iron and steel. We shall 



