136 On the JJpnitle.s of 



If the results of tliis class are compared with those of 

 Class 5, it will be found that an ore compounded of sand and 

 lime is more easily fused, and ultimately more productive, 

 than one equally composed of clav and calcareous earths. 



In these classes I deemed it of some importance to add 

 an eighth. It has of late been received and believed by the 

 most of Europe, that the French chemists have discovered 

 a process of imparting carbonaceous matter to iron by the 

 decomposition of the carbonic acid, and that in such quan- 

 tity as to convert soft iron into cast steel. Those who rest 

 in the belief of this discovery must naturally have expected 

 that in these experiments the greatest quantity of iron would 

 have been revived where the carbonate of lime was used, 

 and iliat this quantify would have borne an exact relation to 

 the proportions of the carbonate. 



The very reverse of this, however, turns out to be the 

 fact ; for it requires double and somelimcs triple the quan- 

 tity of carbonaceous matter to be added to revive the same 

 quantity of iron when carbonate is used, than is requisite 

 with either clay or silex. 



To ascertain what difiercnce would arise betwixt the re- 

 sult of the experiments with chalk, and the same deprived 

 of its acid, the following experiments were made : 



Kegplts of 8th Class, compounded of 

 40 parts of oxide, 

 60 of chalk deprived of its acid. 



Oiiantity of matter (deeming it more unfusible) made use 

 of, 200 grains. 

 iiiXp. \. 1 -30th of carbon yielded no metal. 



— ditto 



— ditto 



— 6 grs. of iron, or 3 per cent. 



— 3/"" ditto 18-i- 



— o3 ditto 26+ 

 not fused. 



If these results are compared with those of Class 1, it 

 will be evident that a larger proportion of charcoal is requi- 

 site in the present case to revive the first portions of iron ; 

 but then it ought lo be conjider(-d that the oxide is pre- 

 sented with a larger proportion of calcareous earth by all 

 the cpiantity of acid and water of crystallization contaiucd 

 hi the carbonate. 



General 



