186 Scientific Intelligence. -^Chemistry. 



nothing else than a combination of pure iron and carburet. 

 The grey kinds contain also graphite. 3. In our high fur- 

 naces, the iron-ores commence with being deoxydised ; the re- 

 gulus of iron presently combines with carbon, and continues to 

 do so, as long as circumstances permit it. This operation of re- 

 duction is accompanied with the formation of enamel, which has 

 a particular influence over the quantity of carbon which the 

 cast-iron may contain, according as it is produced more or less 

 rapidly, is in greater or smaller quantity, more or less vitrified, 

 liquid or thick, and, lastly, according to the nature of its com- 

 ponent principles. 4. In the cast-irons which have but little 

 carbon, the affinity of the iron for that substance is too strong 

 to allow it to separate and form graphite ; such irons, therefore, 

 remain white, even after a slow refrigeration. In those cast-irons 

 which are rich in carbon, on the contrary, that substance sepa- 

 rates during the solidification of the iron, and forms graphite, the 

 particles of which, in intimate mixture with the rest of the mass, 

 give the iron a grey fracture. A sudden refrigeration not allowing 

 this successive formation of graphite, always occasions a white 

 fracture. 5. There are substances which, united with iron, pre- 

 vent this separation of carbon under the form of graphite, such 

 as phosphorus, sulphur, the metallic bases, the earthy oxides, 

 and other metals, especially manganese. In this case, the cast- 

 iron, which contains as much carbon as the greyest iron, and even 

 more, preserves the fracture white, even after the slov, est and 

 best conducted refrigeration possible. 



(2.) Pure Iron. — Forged Iron. Forged iron is considered as 

 pure iron containing foreign substances, especially carbon, in 

 too small quantities to alter its properties. It is the properties 

 more or less noxious which these substances communicate to it 

 which form so many varieties. 



(3.) Steel. — Its chemical composition appears to be identical 

 with that of white cast-iron ; that is to say, it is forixied of pure 

 iron, carbon, and a third body, such as aluminium, silicium, 

 manganese, &c., which renders stable the union of the carbon 

 and iron. The difference between the white cast-iron and steel, 

 appears, according to Mr MuUer, to reside only in the mecha- 

 nical arrangement of the molecules. — Annales des Mines 1826. 



