S/A' WILLIAM SIEMENS, F.R.S. 243 



than -jit per cent, if the metal were not partly protected from the 

 Hunif by the bath of cinder in which it lies ; for in one instance 

 in which the cinder accidentally ran out of a puddling furnace 

 during the balling up of the charge, leaving the iron exposed to 

 the flame, I found the yield reduced from the average of 413 Ibs. 

 down to 370 Ibs., showing an increased waste of 43 Ibs., or over 

 10 per cent., due to the more complete exposure of the metal to 

 the oxidizing action of the flame. 



In order to realize the theoretical result, a sufficient amount of 

 oxides must have been supplied to effect the oxidation of the 

 silicon and carbon of the pig iron, and to form a tribasic silicate 

 of iron (3 Fe 0, Si O 3 ) with the silicic acid produced. 



The amount of oxide required may be readily ascertained. 



In taking the expression, Fe 3 O 4 , the atomic weight of which is 

 3 x 28 + 4 x 8 = 116, while that of the three atoms of iron alone is 

 8 x 28 = 84, it follows that VV x 4G = G3'5 Ibs. of cinder or oxide of 

 iron are requisite to produce the 4G Ibs. of reduced iron which 

 were added to the bath. There must, however, remain a sufficient 

 quantity of fluid cinder in the bath to form, with the silicon 

 (extracted from the iron), a tribasic silicate of iron, or about 

 60 Ibs., making in all 1 24 Ibs. of fettling which would have to be 

 added for each charge, a quantity which is generally exceeded in 

 practice notwithstanding the inferior results universally obtained. 



There remain for our consideration the sulphur and phos- 

 phorus, which being generally contained in English forge pig 

 in the proportion of from '2 to 'G per cent, each, can hardly affect 

 the foregoing quantitative results, although they are of great 

 importance as affecting the quality of the metal produced. 



It has been suggested by Percy that the separation of these 

 ingredients may be due to liquation. This I understand to mean 

 that the crystals of metallic iron, which form throughout the 

 ailing mass when the metal " comes to nature," exclude foreign 

 substances in the same way that the ice formed upon sea water 

 excludes the salt, and yields sweet water when re-melted. 



According to this view, pig metal of inferior quality will really 

 yield iron almost chemically pure, to which foreign ingredients 

 are again added by mechanical admixture with the surrounding 

 cinder, or semi-reduced metal. 



It may be safely inferred that the freedom of the metal from 



R 2 



