150 



IRON. 



remains unchanged in the air ; is not affected by 

 nitric acid, except it be strong and hot ; and is 

 decomposed by charcoal. 



Carburets of Iron. Carbon unites with iron to 

 form steel, cast iron, and graphite, or plumbago. 

 Tin- proportions of carbon corresponding to different 

 carburets of iron, according to Mr Mushet, are as 

 follow : 



soft cast steel. 



common cast steel. 



the same, but harder. 



the same, too hard for drawing. 



white cast iron ; or No. 1. 



mottled cast iron, or No. 2. 



black cast iron, or No. 3. 

 Graphite contains about 10 per cent, of iron. It was 

 remarked above, that the magnetism of pure iron is 

 transient. When it is combined with oxygen, car- 

 bon, or sulphur, however, it acquires the magnet's 

 coercive virtue, which attains a maximum of force 

 with certain proportions of the constituents, hitherto 

 undetermined. Of the alloys which iron unites with 

 other metals to form, tin plate is the most useful. 

 The surface of the iron plates is cleaned, first by 

 steeping in a crude bran-vinegar, and then in dilute 

 sulphuric acid, after which they are scoured bright 

 with hemp and sand, and deposited in pure water to 

 prevent oxidation. Into a pot, containing equal parts 

 of grain and block tin, in a state of fusion, covered 

 with tallow, the iron plates are immersed in a ver- 

 tical position, having been previously kept for about 

 an hour in melted tallow. From 300 to 400 plates 

 are tinned at a time. Each parcel requires an hour 

 and a half for the mutual incorporation of the metals. 

 After lifting out the tinned plates, the striae are re- 

 moved from their surfaces and under edges by subse- 

 quent immersion in melted tin, and then in melted 

 tallow, wiping the surfaces at the same time with a 

 hempen brush. Alloys of steel with platinum, rhodi- 

 um, gold and nickel, may be obtained when the heat 

 is sufficiently high. The alloy with platinum fuses 

 when in contact with steel, at a heat at which the 

 steel itself is not affected. But the most curious cir- 

 cumstances attend the alloy of silver. If steel and 

 silver be kept in fusion together for a length of time, 

 an alloy is obtained, which appears to be very perfect, 

 while the metals are in the fluid state, but, on solidi- 

 fying and cooling, globules of pure silver are ex- 

 pressed from the mass, and appear on the surface of 

 the button. If an alloy of this kind be forged into a 

 bar, and then dissected by the action of dilute sul- 

 phuric acid, the silver appears, not in combination 

 with the steel, but in threads throughout the mass, 

 so that the whole has the appearance of a bundle of 

 fibres of silver and steel, as if they had been united 

 by welding. The appearance of ftiese silver fibres is 

 very beautiful. They are sometimes one eighth of 

 an inch in length, and suggested the idea of giving 

 mechanical toughness to steel, where a very perfect 

 edge may not be required. When 1 of silver and 500 

 of steel are properly fused together, a very perfect al- 

 loy is produced, which, when forged, and dissected 

 by an acid, exhibits no fibres, even when viewed with 

 a high magnifying power, though, by dissolving any 

 portion of the mass in acid, and applying a delicate 

 test, the silver is recognised as being every where 

 present. This alloy proves decidedly superior to the 

 very best steel, and its excellence is unquestionably 

 due to the presence of the silver. Various cutting 

 instruments, as razors, penknives, surgical instru- 

 ments, &c., are now manufactured from it. It is 

 known under the name of silvered steel. Equal parts, 

 by weight, of platinum and steel, form a beautiful 

 alloy, which takes a fine- polish, and docs not tarnish. 



The colour is the finest imaginable for a mirror, 

 The specific gravity of the compound is 9-862. The 

 proportions of platinum that appear to improve steel 

 tor edge instruments are from one to three per cent. 

 The alloys of steel with rhodium would prove highly 

 valuable, were it not for the scarcity of the latter 

 metal. 



Salts of Iron. These are possessed of the follow- 

 ing general properties : Most of them are soluble in 

 water ; those with the protoxide for the base are 

 generally crystallizable; those with peroxide, for the 

 most part, are not so : the former are insoluble, the 

 latter soluble in alcohol. From solutions of these 

 salts ferroprussiate of potash throws down a blue pre- 

 cipitate, or one becoming blue in the air ; infusion of 

 galls gives a dark blue precipitate, or one becoming 

 so in uie air ; hydrosulphuret of potash or ammonia 

 gives a black precipitate ; but sulphureted hydrogen 

 merely deprives the solutions of iron of their yellow- 

 brown colour ; succinate of ammonia gives a flesh- 

 coloured precipitate with salts of the peroxide. We 

 shall notice these salts individually, in an alphabeti- 

 cal order. Protoacetate of iron forms small prismatic 

 crystals, of a green colour and a sweetish taste. 

 Peracetate of iron forms a reddish brown uncrystall- 

 izable solution, much used by the calico printers, and 

 is prepared by keeping iron turnings, or pieces of old 

 iron, for six months, immersed in re-distilled pyrolig- 

 neous acid. Protarseniate of iron exists native in 

 crystals (see Iron Ores), and may be formed in a 

 pulverulent state, by pouring arseniate of ammonia 

 into sulphate of iron. It is insoluble. Perarseniate 

 of iron may be formed by pouring arseniate of am- 

 monia into peracetate of iron, or by boiling nitric 

 acid on the protarseniate. It is insoluble. Antimeni- 

 ate of iron is white, becoming yellow, insoluble ; 

 borate, pale, yellow, and insoluble ; benzoate, yellow 

 and insoluble ; protocarbonate, greenish and soluble ; 

 percarbonate, brown and insoluble ; chromate, black- 

 ish and insoluble ; prolocitrate, brown, crystals 

 soluble ; protoferroprussiate, white, insoluble. The 

 perferroprussiate is the beautiful pigment called 

 Prussian blue. When exposed to a heat of 400 

 Fahr., it takes fire in the open air ; but in close ves- 

 sels it is decomposed, apparently, into carbureted 

 hydrogen, water, and hydrccyanate of ammonia, 

 which come over while a mixture of charcoal and 

 oxide of iron remains in the state of a pulverulent 

 pyrophorus, ready to become inflamed on contact with 

 the air. Prussian blue is of an extremely deep blue 

 colour, insipid, inodorous, and considerably denser 

 than water. Neither water nor alcohol have any 

 action on it. It is usually made by mixing together 

 one part of the ferrocyanate of potash, one part of 

 copperas, and four parts of alum, each previously 

 dissolved in water. Prussian blue, mingled with 

 more or less alumina, precipitates. It is afterwards 

 dried on chalk stones in a stove. When sulphuric 

 acid is added to Prussian blue, it makes it perfectly 

 white, apparently by abstracting its water ; for the 

 blue colour returns on dilution of the acid; and if the 

 strong acid be poured off, it yields no traces of either 

 prussic acid or iron. Protogallate of iron is colour- 

 less and soluble ; pergallate, purple and insoluble ; 

 protomuriate, green and crystallizable, very soluble ; 

 permuriate, brown, uncrystallizable, very soluble 

 (see Chlorides of Iron, previously described); pro- 

 tonitrate, pale green, soluble ; pernitrate, brown, 

 soluble ; protoxalate, in green prisms, soluble; pcrox- 

 alate, yellow, scarcely soluble ; protophosphate , blue, 

 insoluble; perphosphale, white, insoluble; protosuc- 

 cinate, in brown crystals, soluble; persuccinnte, 

 brownish red, insoluble. Protostilphate, or green vit- 

 riol, or copperas, is obtained by putting iron into an 

 aqueous sulphurous acid, and letting them remain 



