TRANSACTIONS OF THE SECTIONS. 51 



Graphite ( A). White Cast Iron 



Carbon 



c-i- > Carburet of silicon. 



I 



cTbon^^^^^"^'^*°^^^°"- 



Azote 1 



Silicon > Carburet of silicon. 



Carbon J 



It was further shown, that all gray iron, produced by heated air as 

 well as by cold air, left a grayish white residue behind after treating it 

 with hydi'ochloric acid of a certain specific gravity. This remainder, 

 acted upon with caustic ammonia, evolved very rapidly pure hydrogen 

 gas, and alumina afterwards was found in the solution with a little 

 silica. The presence of aluminum in its metallic state, after having 

 been treated Avith acid, as well as the absence of all azote, seemed to 

 be one principal feature of gray iron of France as well as of England; 

 on the contrary, carbon, hydrogen, and azote are always present in 

 the remainders of ^vhiie iron, which remainders appear invariably of a 

 brownish colour; and azote is a constituent of steel as well as of 

 wrought iron. Further, it was explained, that silicon generally was 

 combined with carbon, and dissolved in the carburets of iron, and that 

 it was extremely difficult to produce an alloy of iron with silicon alone, 

 without the presence of a little carbon, aluminum, and other similar 

 bodies. Dr. Schafhaeutl found the molecules of all iron of a similar 

 form, belonging to the cubical system, and the largest not exceeding 

 0'0000633 of an inch in diameter, and that particularly upon the ar- 

 rangement of these molecules depends, in a great measure, the different 

 appearance of the different kinds. He denied that any graphite scales 

 were to be seen in gray cast iron ; yet, that under a magnifying glass 

 what appeared to the naked eye graphite scales, were really surfaces 

 and planes of crystallization, composed of pentagonal planes not wider 

 in the smallest diameter than 0'000355 of an inch, and composed of 

 the before-mentioned smallest or primitive iron molecules. According 

 to his statement, the molecules of the iron are arranged in the gray cast 

 iron in the most regular form, having all their surfaces in continuous 

 planes ; the most equal distribution of molecules appeared in hardened 

 steel ; collecting in fascicular aggregation in soft steel, and being loose 

 and longitudinally arranged in wrought iron. He stated that pure iron 

 could not be welded ; that the welding power of iron depended on its 

 alloy with the carburet of silicon, and also that the good and various 

 qualities of all the v.rought irons depended on the alloys of pure iron 

 with other metallic bodies ; and that the presence of most of the elec- 

 tro-negative metals had been generally overlooked in the published 

 analyses of iron. The presence of arsenic in Swedish steel, when forged 

 red hot, could be ascertained by its smell, as well as in the Low Moor 

 iron. The usual solution of iron under analysis, in order to separate 

 those metals from the iron, must be, for the necessary connection, 

 divided into two parts, — one to be treated with a current of sulphuret- 

 ted hydrogen, the other part dropped into the sulphydrate of ammonia, 

 and carefully digested. A small quantity of silica was more difficult 

 to separate from a large quantity of iron than generally seemed to be 



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