ON PUDDLING IRON. 61 
whereas the final metal contained only +296 of silicon and carbon, showing 
a gain of metal of 
5°5 —:296 =5-204 per cent., 
or, including the 5 lbs. of increased weight, a total gain of 5-7 per cent. of 
metallic iron. 
Supported by these observations, I venture to assert that the removal of the 
Silicon and Carbon from the pig iron in the ordinary puddling or “ boiling” 
process is due entirely te the action of the fluid oxide of won present, and that 
an equivalent amount of metallic iron is reduced and added to the bath, which 
gain, however, is generally and unnecessarily lost again in the subsequent 
stages of the process. The relative quantity of metal thus produced from the 
fluid cinder admits of being accurately determined. 
The cinder may be taken to consist of Fe* O* (this being the fusible com- 
bination of peroxide and protoxide), together with more or less tribasio sili- 
cate (3 FeO, SiO*), which may be regarded as a neutral admixture, not 
affecting the argument, and silicic acid or silica is represented by Si 0°, from 
which it follows that for every four atoms of silicon leaving the metal, nine 
atoms of metallic iron are set free; and taking the atomic weights of iron 
= 28, and of silicon= 22:5, it follows that for every 
4 x 22°5=90°0 
grains of silicon abstracted from the metal, 
9 x 28 = 252 
grains of metallic iron are liberated from the cinder. 
Carbonic oxide, again, being represented by CO, and the cinder by Fe’* 0%, 
it follows that for every four atoms of carbon removed from the metal three 
atoms of iron are liberated; and taking into account the atomic weights of 
carbon=6 and of iron=28, it follows that for every 
6x4=24 
grains of carbon oxidized, 
28 x 3=84 
grains of metallic iron are added to the bath. Assuming ordinary forge pig, 
after being remelted in the puddling-furnace, to contain about 3 per cent. of 
carbon and 2 per cent. of silicon, it follows from the foregoing that in re- 
moving this silicon 
252 : 2 
90 * 2=5°6 per cent., and in removing the carbon 
84 
9g X3=105 
per cent. of metallic iron is added to the bath, making a total increase of 
56410'5—5=11'1 
per cent., or a charge of 420 lbs. of forge pig metal ought to yield 466 lbs. 
of wrought metal, whereas from an ordinary puddling-furnace the actual 
yield would generally amount to only 370 lbs. (or 12 per cent. less than the 
charge), showing a difference of 96 lbs. between the theoretical and actual 
yield in each charge. 
This difference, amounting to fully 20 per cent., is due to the enormous 
waste by oxidation to which the iron is exposed after it has been “ brought 
to nature” (by the removal of the carbon), when it is in the form of a 
granular or spongy metallic mass and during the process of forming it into 
balls. So great a waste of metal by oxidation seems at first sight almost 
incredible ; but considering the extent of surface exposed in the finely divided 
puddled mass, it is not at all exceptional, and is in fact almost unavoidable 
in a furnace of the ordinary construction, maintained as a puddling-furnace 
_is at a welding heat. Many attempts have been made (for example, by 
