I R O 
conceals all together. It. is then taken while 
hot, and hammered violently, by means of a 
heavy hammer driven by machinery. This 
not only makes the particles of iron approach 
nearer each other, but drives away several 
impurities wh ch would otherwise continue 
attached to the iron. 
In this state it is the substance described 
under the name of iron. As it has never yet 
S 'been decomposed, it is considered at present, 
when pure, as a simple body; but it has sel- 
dom or never been found without some small 
[mixture of foreign substances. These sub- 
jj stances are either some of tire other metals, 
or oxygen, carbon, or phosphorus. 
When small pieces of iron are stratified in 
a close crucible, with a sufficient quantity of 
charcoal-powder, and kept in a strong red 
heat for eight or ten hours, they are convert- 
ed into steel, which is distinguished from iron 
bv the following properties. 
It is so hard as to be unmalleable while 
cold* or at least it acquires this property by 
being immersed while ignited into a cold li- 
quid: for this immersion, though it has no 
effect upon iron, adds greatly to the hardness 
I of steel. 
It is brittle, resists the file, cuts glass, af- ' 
[fords sparks with Hint, and retains the mag- 
! netie virtue for any length of time. It loses 
this hardness by being ignited and cooled 
very slowly. It melts at above 130° Wedge- 
wood. It is malleable when red-hot, but 
scarcely so when raised to a white heat. It 
may be hammered out into much thinner 
plates than iron. It is more sonorous; and 
its specific gravity, when hammered, is greater 
than that of iron. 
By being repeatedly ignited in an open 
vessel, and hammered, it becomes wrought 
iron, which is a simple; substance, and if 
perfectly pure would contain nothing but 
iron. 
Steel is iron combined with a small portion 
of carbon, and has been for that reason called 
c arbureted iron. The proportion of carbon 
has not been ascertained with much preci- 
sion. From the analysis of Vauquelin, it 
•annfcnts, at an average, to T ^._ part. Mr. 
Clouet seems to affirm that it amounts to 
_i ( _ part ; but he has not published the expe- 
riments which led him to a proportion, which 
so far exceeds what has been obtained by 
other chemists. 
That steel is composed of iron combined 
with pure carbon, and not with charcoal, has 
been demonstrated by Morveau, who formed 
steel by combining together directly iron and 
diamond. At the suggestion of Clouet, he 
Inclosed a diamond in a small crucible of 
pure iron, and exposed it completely covered 
up in a common crucible to a sufficient heat. 
The diamond disappeared, and the iron 
was converted into steel. The diamond 
weighed 907 parts, the iron 57800, and the 
ste> l obtained 50384; so that 2313 parts .of 
the iron had been lost in the operation. 
From this exp riinent it follows, that steel 
contains about of its weight of carbon. 
This experiment was objected to by Mr. 
Mushet, buttiie objections were fully refuted 
by sir George M‘Kj?nzie. 
Rinman, long ago, pointed out a method 
by which steel may he distinguished from 
' iron. W hen a little diluted nitric acid is 
Y O L. II. 0 
T R O 
dropt upon a plate of steel, allowed to remain 
a few minutes, and then washed off, it leaves 
behind it a black spot ; whereas the spot 
formed by nitric acid on iron is whitish-green. 
We can easily see the reason of the black 
spot: it is owing to the carbon of the iron 
which is converted into charcoal by the acid. 
This experiment shows us, that carbon is 
much move readily oxidated when combined 
with iron lliau when crystallized in .the dia- 
mond. 
Cast iron, is iron combined with a still 
greater proportion of carbon than is necessary 
for forming steel. The quantity has not yet 
been ascertained with precision : Mr. Clouet 
makes it amount to -i of the iron. The 
blackness of the colour, and the fusibility of 
cast iron, are proportional to the quantity of 
carbon which it contains. Cast iron is almost 
always contaminated with foreign ingredi- 
ents: these are chiefly oxide of iron, plios- 
phuret of iron, and silica. 
It is easy to see why iron is obtairied from 
its ore in the state of cast iron. The quan- 
tity of charcoal, along with which tin* ore is 
fused, is so great, that the iron has an oppor- 
tunity of saturating itself with it. 
The conversion of cast iron into wrought 
iron is effected by burning away the char- 
coal, and depriving the iron wholly of oxygen : 
this is accomplished by heating it violently 
while exposed to the air. Mr. Clouet has 
found, that when cast iron is mixed with ± 
of its weight of black oxide of iron, and heat- 
ed violently, it is equally converted into pure 
iron. The oxygen of the oxide, and the car- 
bon of the cast iron, combine, and leave the 
iron in a state of purity. 
The conversion of iron into steel is effected 
by combining it with carbon. This combi- 
nation is performed in the large way by 
three different processes, and the products 
are distinguished by the names of natural 
steel, steel of cementation, and cast steel. 
Natural steel is obtained from the ore by 
converting it flrst into cast iron, and then ex- 
posing the cast iron to a violent heat in a fur- 
nace while its surface is covered with a mass 
of melted scorix live or six inches deep. 
Part of the carbon combines with the oxygen 
which cast iron always contains, and flies off 
in the state of carbonic acid gas. The re- 
mainder combines with the pure iron, and 
constitutes it steel. 'Phis steel is inferior to 
the other species; its quality is* not the same 
throughout ; it is softer, and not so apt to 
bre k; and as the processes by which it is 
obtained are less expensive, it is sold at a low- 
er price than the other species. 
It is obvious that iron and carbon are ca- 
pable of combining together in a variety of 
different proportions. When the carbon ex- 
ceeds, the compound is carburet of iron, or 
plumbago. When the iron exceeds, the 
compound is steel or cast iron in various 
states, according to the proportion. All these 
compounds mav be considered as subcarbu- 
rets of iron. The hardness of iron increases 
with the proportion of charcoal with which 
it combines, till the carbon amounts to about 
of the whole mass. The hardness is then 
a maximum; the metal acquires the colour 
of silver, loses its granulated appearance, 
and assumes a crystallized form. It mere 
carbon is added to the compound, the hard- 
I S O 33 
ness diminishes in proportion to its quan- 
tity. 
"The affinities of iron, and its oxides, are 
arranged by Bergman as in the following 
Oxide of Ikon. 
Oxalic acid. 
Tartaric, 
Camphoric, 
Sulphuric, 
Saclatic, 
Muriatic, 
Nitric, 
Phosphoric, 
Arsenic, 
Fluoric, 
Succinic, 
Citric, 
Lactic, 
Acetic, 
Boracic, 
Prussic, 
Carbonic. 
Iron -sick, in the sea-language, is said of 
a ship or boat, when her bolts or nails are so 
eaten with rust, and so worn away, that they 
occasion hollows in the planks, whereby the 
vessel is rendered leaky. 
IRRATIONAL, an appellation given to 
surd numbers and quantities. See Alge- 
bra. 
IRREGULAR, in grammar, such in- 
flections of words as vary from the general 
rules ; thus we say, irregular nouns, irregular 
verbs. 
ISATIS, woad ; a genus of the siliquosa 
order, in the tetradynamia class of plants ; 
and in the natural method ranking under the 
39th order, the siliquosa. The siliqua is lan- 
ceolated, unilocular, monospemious, bivalv- 
ed, and deciduous ; the valves navicular or 
canoe-shaped. There are four species; but 
the only one worthy of notice is the tinctoria, 
or common woad, which is cultivated in seve- 
ral parts of Britain for the purposes of dye- 
ing, being used as a foundation for many of 
the dark colours. See Dyeing. 
ISCILEMUM, a genus of the monoecia 
order, in the polvgamia class of plants ; and 
in the natural method ranking under the 4th 
order, gramina. The calyx of the Her- 
maphrodite is a biflorous glume; the corolla 
bivalved ; there are three stamina, two styles, 
and one seed. The calyx and corolla of the 
male, as in the former, with three stamina. 
There are eight species. 
I SCI JURY. See Medicine. 
ISEltTIA, a genus of the hexandria mo- 
nogvnia class and order ; the cal. is coloured, 
four or six toothed ; cor. six-cleft, funnel- 
form ; pome subglobular, six-celled. There 
is one species, a tree of Cayenne. 
ISINGLASS, in the materia medica, &e. 
See Accipenser. 
ISXARDTA, a genus of the monogynia 
order, in the tetrandria class of plants; and 
in the natural method ranking under the 17th 
order, calycanthemax There is no corolla ; 
the calyx is quadrifid ; the capsule qtiadrilo- 
cular, and girt with the calyx. There is one 
species, an aquatic and annual. 
1SOCELES Triangle, in geometry, one 
that lias two equal sides. 
ISOCHRONAL, Isochrone, or Tsd- 
Iron. 
Nickel, 
Cobalt, • 
Manganese, 
Arsenic, 
(Copper, 
G old. 
Silver, 
Tin, 
Antimony, 
Platinum, 
Bismuth, 
Li ad, 
Mercury. 
