CHEMISTRY. 



23 



i.lemen;j ne tic properties entirely. This is known w th respect 

 to iron saturated with sulphur and carbon, and is pro- 



'_?-""-?' bable w ' tn respect to iron saturated with phosphorus. 

 The subject requires and deserves farther investiga- 

 tion. 



There are a great many varieties of iron, which ar- 

 tists distinguish by different names ; but they may 

 be all reduced under the following classes : Cast iron, 

 wrought or soft iron, and steel. 



Cart irou. Cast iron, or jiig irnn, is the name of the metal 

 when first extracted from its ores. The ores of iron 

 commonly used, are a mixture of the oxide of the me- 

 tal and clay. They are reduced to small pieces, and 

 exposed to a violent heat, mixed with charcoal and 

 lime. The charcoal separates the oxygen, while the 

 lime, combining with the clay, forms a liquid through 

 winch the melted iron falls, and is collected at the 

 bottom of the furnace. It is let out and cast in 

 moulds. The cast iron thus obtained, varies consi- 

 derably according to circumstances. Three varieties 

 have been well distinguished ; namely, white cast 

 iron, which is very hard and brittle ; grey or mot- 

 tled, which is softer and less brittle ; and black, 

 which is the softest and most fusible. Cast iron 

 melts at 1:30" Wedgewood. Its specific gravity va- 

 ries from 7.2 to 7.6. It contracts considerably 

 when brought into fusion. 



Cast iron is converted into wrought or fft irnn, 

 by keeping it melted for a considerable time in a bed 

 of charcoal and ashes, and the scoriae or black oxii/e 

 of iron, and then forging it repeatedly till it becomes 

 compact and malleable. In this state, it is the sub- 

 stance described in the beginning of this Section un- 

 der the name of iron. It is considered when pure 

 as a simple body ; but it is difficult to procure it 

 quite pure. It is almost always contaminated with 

 some foreign body, either some of the other metals, 

 or nxyjrcn, carbon, or phosphorus. 



When soft iron is kept red hot for ome time in a 

 bed of charcoal, it is converted into stret. Steel is 

 so hard, as to be unmalleable while cold. It is 

 brittle, resists the file, cuts glass, strikes fire with 

 flint, and retains the magnetic virtue when impregna- 

 ted with it. It is more sonorous ; and its specific 

 gravity is greater than than that of soft iron. It va- 

 ries from 7.78 to 7.84. 



Steel. These different states of iron have been long known, 



and many attempts were made to ascertain the cause 

 of the differences among them. At last it was re- 

 cognised by Bergman and the French chemists. 

 Soft iron is the simple metal. Stfrl is iron combined 

 with a portion of carbon, and has been for that reason 

 called rubcarlmrct of iron. The carbon, from Vauque- 



Alloys 



lin's analysis, amounts to - 



part of the whole. 



Cast iron is iron combined with a still greater pro- 

 portion of carbon. It usually contains likewise a lit- 

 tle oxygen. 



4. Iron does not combine with azote. 



5. Iron unites with most of the metals. Gold 

 combine* readily with iron, and forms a ductile alloy 

 of a pale yellow or white colour, according to the 

 proportions. Platinum is found usually alloyed with 

 iron, but it is difficult to combine the two metals ar- 

 tificially, on account of the high temperature neces- 

 sary to fuse them. Silver and iron combine, and 



form a ver> hard alloy of a white .colour. Mercury Element! 

 does not readily unite to iron, but an amalgam may C | lc 

 be formed artificially. Iron may be united to cop- 

 per by fusion, but not without considerable difficul- 

 ty. The alloy is grey, imperfectly ductile, and very 

 infuxible. It is probable that the variety of iron 

 called holshort, because it is brittle when red hot, 

 owes that property to the presence of a little copper 

 with which it is alloyed. 



SECT. XI. OfNicM. 



Nickel was first recognised as a peculiar metal, in Nickel. 

 consequence of the experiments of Cronstedt in 1751. 

 It is obtained from an ore which occurs in different 

 German mines, and called knpjer nickel, or false cop- 

 per, because it resembles copper, though no copper 

 can be extracted from it. It has been examined by 

 many eminent chemists, especially by Richter, to 

 whom we are indebted for the most exact account of 

 its properties. 



1. Nickel has a white colour like silver; it is softer Propertied 

 than iron ; its specific gravity, when hammered, is 



8.820. It is malleable both cold and hot, and may 

 be easily hammered out into thin plates. It is pow- 

 erfully attracted by the magnet, and may be convert- 

 ed into a magnet precisely like bars of steel. It re- 

 quires for fusion a temperature at least equal to 160 

 of Wodtrewood. It is not altered by air nor water. 



2. When moderately heated, it tarnishes ; and, if Oxides: 

 in powder, may be even converted into an oxide ; 



but a strong heat reduces it again to the metallic 

 state. We are at present acquainted with two ox- 

 ides of nickel, the grfy ard the black. 



The protoxide may be obtained by dissolving nic- 

 kel in nitric acid, precipitating the oxide by carbon- 

 ate of potaih, washing it, and exposing it to a slight 

 red heat. It is of an ash grey colour, and is com- 

 posed of 78 nickel, and 22 oxygen. It is tasteless, 

 soluble in muriatic acid, and the solution is grass 

 green. It dissolves likewise in ammonia. 



The peroxide may be formed by mixing the prot- 

 oxide with water, and passing a current of chlorine 

 gas through the liquid. A portion of the oxide dis- 

 solves, and a portion acquires a black colour. When 

 thin black oxide is dissolved in acids, an effcrvetcence 

 takes place, owing to the escape of a portion of its 

 oxygen. 



3. Nickel has not been combined with hydrogen. 

 It is always united with carbon, and it unites readily 

 with phosphorus and sulphur. Cronstedt formed 

 sulphuretof nickel by fusion. The phosphuret may 

 be obtained by dropping bits of phosphorus on red 

 hot nickel. 



4. Nickel does not unite with the simple incom- 

 bustibles. 



5. The alloys which it forms are but imperfectly 

 known. They are mostly brittle and hard, and have 

 been applied to no useful purpose. 



SECT. XII. Of Tin. 



Tin was known to the ancients, and was imported Ti. 

 from Britain at a very early period by the Phrui- 

 ciani. 



