ON PUDDLING IRON. 59 
hammer-slag or red ore, thrown in expressly with the charge, that the 
silicon is first separated from the iron, that the carbon only leaves the iron 
during the “boil” or period of ebullition, and that the sulphur and phos- 
phorus separate last of all while the metal is “ coming to nature.” 
The investigations by Price and Nicholson and by M. Lan confirm these 
results, from which Dr. Percy draws some important general conclusions, 
which have only to be followed up and supplemented by some additional 
chemical facts and observations in order to render the puddling process per- 
fectly intelligible, and to bring into relief the defective manner in which it is 
at present put into practice, involving, as it does, great loss of metal, waste 
of fuel and of human labour, and an imperfect separation of the two hurtful 
ingredients, sulphur and phosphorus. 
Silicon.—In forming (by means of the rabble) an intimate mechanical 
mixture between the fluid cast metal and the cinder, the silicon contained in 
the iron is brought into intimate contact with metallic oxide, and is rapidly 
attacked, being found afterwards in the cinder in the form of silicic acid 
(combined with oxide of iron). The heat of the furnace is always kept low 
during this stage of the process, and the flame is maintained as reducing as 
ossible. 
4 Carbon.—The disappearance of the carbon from the metal is accompanied 
by the appearance of violent ebullition and the evolution of carbonic oxide, 
which rises in innumerable bubbles to the surface of the bath, and burns (in 
an ordinary puddling-furnace) with the blue flame peculiar to that gas. In 
puddling in a regenerative gas-furnace this blue flame cannot be observed, 
because the flame of this furnace is strictly neutral, and there is no free 
oxygen present to burn the carbonic oxide rising from the fluid mass—a cir- 
cumstance which by itself explains the superior results obtained from the 
gas furnace. 
It is popularly believed that the oxygen acting upon the silicon and carbon 
of the metal is derived directly from the flame, which should, on that account, 
be made to contain an excess of oxygen ; but the very appearance of the pro- 
cess proves that the combination between carbon and oxygen does not take 
~place on the surface, but throughout the body of the fluid mass, and must be 
attributed to the reaction of the carbon upon the fluid cinder in separating 
from it metallic iron ; while as the removal of the silicon is still more rapid, 
and is effected under a reducing flame, there is strong evidence that it also is 
oxidized rather by the oxygen of the cinder than by the flame*. 
But it has been argued that, although the reaction takes place below the 
surface, the oxygen may, nevertheless, be derived from the flame, which may 
oxidize the iron on the surface, forming an oxide or cinder, which is then 
transferred to the carbon at the bottom, in consequence of the general agita- 
tion of the mass. 
This view I am, however, in a position to disprove by my recent expe- 
rience in melting cast steel upon the open flame-bed of a furnace, having 
invariably observed that no oxidation of the unprotected Jud metal takes 
place so long as it contains carbon in however slight a proportion. 
But being desirous to ascertain by positive proof what is the behaviour of 
silicon and carbon in fluid cast iron when contact with the atmosphere or 
the flame of the furnace is strictly prevented, I instituted the following ex- 
_ periment at my Sample Steel Works at Birmingham ;— 
* At the end of this paper is appended a Table showing the comparative quantities of 
carbon in various kinds of iron and steel. 
F2 
