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XLVIII. On the Solution of various Kinds of Steel and Iron in 

 Acids ; and on the Nature of the Residuums left by them. By 

 M. Karsten*. 



THHE action of the acids on steel depends on the degree of 

 -*- hardness which the steel has received. Steel, hardened to 

 the utmost of its capacitj', is dissolved with very great difficulty 

 and slowness in diluted acids. In diluted muriatic acid, it 

 becomes covered after a few days with a black powder ; and 

 the solution makes so little progress within the space of 

 several weeks, that it would seem to require many months 

 before it is completed. White raw iron shows absolutely the 

 same habitudes as steel, only that the effects ai'e more striking. 

 Diluted muriatic or sulphuric acids have scarcely any effect 

 on this kind of iron, on which the black powder does not ap- 

 pear until after the expiiation of several weeks. Strong muriatic 

 acid, aided by a boiling heat, produces a solution without 

 leaving any residuum. Sulphuric acid, under similar circum- 

 stances, leaves some carbon of a black colour and with a metallic 

 appearance. Nitric acid at common temperatures separates 

 black flakes, which by a longer exposure to the acid turn to 

 a brownish-red. By boiling, a violent effervescence is pro- 

 duced, together with the other circumstances just mentioned. 



Very different from this are the habitudes of gray raw iron 

 to the acids. Diluted muriatic and sulphuric acids act but 

 vex'y slowly, and leave at the lapse of several months a residuum 

 containing carbon in very different conditions. One part con- 

 sists of very thin leaves or scales, of a perfectly metallic ap- 

 pearance and strong lustre. They resist the effects of acids 

 and alkalies of every description, are not in the least attracted 

 by the magnet, and are very slowly consumed in a red-hot 

 platinum crucible. This body has been long known as gra- 

 phite. Another part of the carbon has indeed also the graphitic 

 appearance, but is subject to magnetic influence, and is in 

 every respect like the residuum left by soft steel when treated 

 with the acids. A third portion, in fine, has a black colour, 

 is not magnetic, colours a caustic alkaline solution black, and 

 is consumed before the crucible becomes ignited. Among 

 these three bodies the graphite is never missmg; whilst, of the 

 two other combinations, one only generally appears in the re- 

 siduums. 



Strong muriatic acid produces a more rapid solution, 

 rendered still more so by boiling. The hydrogen disengaged 

 by it, mechanically carries up the graphite with it in the solu- 



* From Schweigger's Journal, Band xiii. p. 335. 



tion. 



