178 ANNUAL OF SCIENTIFIC DISCOVERY. 



of iron, as has hitherto been supposed, but that there exists a series 

 of combinations of iron with metalloids, metals, and even with cyan- 

 ides, yielding steel of very good quality. He states, in the first place, 

 that steel, when dissolved in acids, leaves a residue different from 

 pure carbon, but closely resembling certain cyanides. He then pro- 

 ceeds to show that if common iron, in its metallic state, be subjected 

 for the space of two hours to the action of common illuminating gas 

 (carburetted hydrogen) at a red heat, the iron is carbonized and 

 transformed into cast iron, of a gray color, very malleable, and equal 

 to the best specimens produced by charcoal. But if the same gas be 

 brought into contact with nitrogenized iron (nitride of iron), then, 

 instead of cast iron, steel is produced, the good or bad quality of 

 which entirely depends on the quantity of nitrogen previously 

 combined with the iron ; if that quantity is sufficient, the result is 

 steel of the finest grain. If, instead of previously nitrogenizing and 

 afterwards carbonizing the metal, a mixture of ammonia and illu- 

 minating gas be brought into contact with common iron at a red heat, 

 it then at once absorbs nitrogen from the ammonia, and carbon from 

 the carburetted hydrogen, and steel is obtained of a quality corres- 

 ponding to the relative proportion of the two gases. Here, therefore, 

 the process of cementation, instead of being effected by charcoal, is 

 accomplished by a gas proceeding from pit-coal. If, conversely, steel 

 be heated in an atmosphere of hydrogen, it loses its nitrogen, and 

 ammonia is produced. Hence, M. Fremy concludes that steel is not 

 a simple carburet, but nitro-carburetted iron ; and this is true not 

 only of steel produced in laboratories, but of the common market 

 article. 



At the conclusion of the reading of this paper in the French 

 Academy, M. Dumas spoke on the important results which must flow 

 from these discoveries of M. Fremy. The theory of the production 

 of steel, he said, seemed henceforth determined, and it might reason- 

 ably be hoped that great practical results would ensue. Who, for 

 instance, did not forsee and it was for M. Fremy to follow out the 

 demonstration that great advantage would result from these new, 

 methodical, regular, and certain processes, when there was occasion 

 either to case-harden the surface or edge of certain iron implements 

 or instruments ? After having forged, filed, and finished them off in 

 the state of iron, a current of ammouiacal and carburetted gases 

 would convert them more or less completely into steel ; the depth of 

 the stratum of steel being regulated by the duration of this gaseous 

 cementation with a certainty never obtainable by cementation with 

 powders, or by the use of horn or animal matters in the empirical 

 processes. 



M. Morin remarked that M. Fremy's researches explained numer- 

 ous empirical receipts and processes for the cementation of steel. In 

 most of these processes, mixtures were employed containing various 

 proportions of carbon, and of more or less nitrogenized substances, 

 such as ammoniacal salts, horn shavings, leather cuttings, soot, etc., 

 etc., the result being a cementation more or less deep, according to 

 the use to which the instruments are to be applied. He thought it 

 necessary, also, to observe that the character of steels produced by 

 different methods varied greatly, not only where these methods dif- 



