IRON. 
solids by the application of a fluid, which 
afterward becomes consistent. And as pla- 
tina possesses this valuable property, it 
seems reasonable to infer, that it must also 
consist of two metallic substances of differ- 
ent degrees of fusibility ; a supposition that 
appears to be confirmed by the discoveries 
of Dr. Wollaston and Mr. Tennant. 
Crude iron, and steel of a uniform tex- 
ture, consist therefore of a fusible combina- 
tion of iron with the combustible substance 
of the coal, or something which is imparted 
from it ; the crude iron differing from the 
steel simply in being overdosed with car- 
bon, and less pure, on account of the ad- 
mixture of metallic oxide, which can scarce- 
ly, perhaps, be avoided in the large process. 
It appears therefore, that crude iron must 
pass through the state of steel, before it can 
become forged iron; and consequently, that 
the fabrication of steel from this last is a 
circuitous process, which can only be re- 
paid by the absence of those unreduced 
parts, which may exist in the crude iron. 
At some forges, however, where the ore, 
the flux, the fuel, and the management, are 
adapted to each other, the produce affords 
steel, when duly refined. At other manu- 
factories, the crude iron is either refined 
or converted into steel, by running it into 
thin plates, which are stratified with char- 
coal, and burned in a close furnace. In 
this way the metal is refined by degrees 
without undergoing fusion; and if the heat 
be raised to that of cementation, the iron 
will not only be reduced, but converted into 
steel. In the forges of Carinthia the grey 
crude iron is also converted either into soft 
iron, or steel, according to the management 
of a somewhat similar process. The iron 
is fused in a large melting-pot; and a small 
quantity of water, being thrown upon the 
surface of the metal, causes a thin plate to 
congeal, which is taken off; and by con- 
tinuing the operation, the greatest part of 
the fused iron becomes converted into 
plates. To produce steel, these plates are 
again fused, and kept a long time in an 
elevated heat; at the same time that the 
metal is defended from the contact of the 
air by a sufficient quantity of the vitreous 
slag. To produce soft iron, the plates are 
exposed to a continued roasting, while the 
air is constantly renewed by means of two 
pair of bellows. The extensive surface of 
the plates renders it unnecessary to use 
that agitation, or stirring, which is required 
when fused crude iron is refined. In these 
processes it is evident, that the same mat. 
VOL. Ill, 
ter in the crude iron, which it obtained in 
the smelting furnace, is employed, and sup- 
plies the place of the charcoal used in form- 
ing steel by cementation ; and on the other 
hand, that this substance, which prevented 
the crude iron from being soft, tough, and 
infusible, is burned away, together with a 
portion of the iron itself, while the remain- 
der is left in a much purer state. 
These are facts observed at the furnaces. 
But the observations and inquiries of the 
chemist must be carried further, in order to 
determine what it is that iron gains or loses 
at the time of its conversion into its va- 
rious states. It is found, that crude iron ap- 
proaches towards the soft state, not only by 
heating with exposure to the air, which 
burns the combustible addition, but like- 
wise by fusion, without the free access of 
air. In this case, when the fusion has been 
complete, and the cooling gradual, it is 
found that a black substance is thrown up 
to its surface, which is more abundant the 
greyer or blacker the iron; and the same 
black substance is observed to coat the 
ladles of forged iron, which are used to 
take out the metal, and pour it into moulds 
for casting shot, and other articles. It ap- 
pears, therefore, that the heated iron, like 
other heated fluids, is capable of holding a 
larger quantity of matter in solution than 
when cold; and that a- portion of this 
black substance separates during the cool- 
ing, whether by the gradual effect of sur- 
rounding bodies, or by the contact of the 
ladle, in the same manner as various salts 
are separated, in part, from water, by a di- 
minution of temperature. From chemical 
analysis, as well as from its obvious charac- 
ters, this black substance is found to be 
plumbago, or the materials used to make 
pencils, and commonly known by the name 
of black lead, which is nothing but a car- 
buret of iron. 
The presence of this black matter is like- 
wise exhibited by dissolving steel, or crude 
iron, in acids, in which plumbago is inso- 
luble, and therefore remains behind in the 
form of a powder. Hence likewise is de- 
duced the cause of the black spot which 
remains upon steel, or crude iron, after its 
surface has been corroded by acids ; for this 
spot consists of the plumbago, which remains 
after the iron has disappeared by solution. 
Solution in the sulphuric or muriatic acid 
not only exhibits the plumbago contained 
in iron, but likewise possesses the advantage 
of showing the state of its reduction by the 
quantity of hydrogen gas which is disen- 
Tt 
