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trace





Silica (Si0 2 )


4-55








5-130


Carbonic anhydride (CO-.)





2-96








Phosphoric (P 2 Oo)


0-03


trace


trace


0-032


Sulphuric (SOJ




O'll


0-09




Sulphur (S)











0-075


Pyrites (FeS,) .


0-47





0-03





Water (H,0)








0-56





Organic matter .














Insoluble residue





6-55


5-18










100-56


100-88


-













Metallic iron per cent.


66-42o/


60-55%


65-98%


59-526



A. Barrow- in-Furness (Richards).
Ulverstone (Spiller). D. Canadian.



B. Ulverstone (Dick). C.



In the North Lonsdale district the ores average from 52
to 54 per cent, of metallic iron, the highest yielding from
60 to 62 per cent., whilst the poorest contain about 40 per
cent.

The most important deposits of red haematite are found
in the Cambrian, Silurian, Devonian, and Carboniferous rocks ;
the deposits of North Lancashire and Cumberland occur in
veins in the limestone and Silurian systems, and at Eskdale
in granite. Bed haematite is often associated with the brown
oxides, and the ore is classed as hard or soft, according as it
contains free silica in excess or otherwise. The more import-
ant Continental and foreign deposits of these ores occur in
Spain, Canada, and the United States.

Brown Haematite. Brown haematite (limonite), or brown



IRON.



iron-ore, is when pure a hydrated ferric oxide, represented
by the formula 2Fe 3 3 3H.,0, and would thus yield 59 '89 per
cent, of metallic iron. It has a dull lustre, and varies from
blackish- to yellowish-brown, but it affords an invariable
yellowish-brown streak. It occurs in irregular, compact, more
or less homogeneous masses, in the Carboniferous limestone and
lower Coal Measures of the Forest of Dean, Gloucestershire, and
Glamorganshire ; whilst a less pure variety, containing more or
less mechanically mixed sand, occurs in the Lias, Oolites, and
Lower Greensands of Northamptonshire, Lincolnshire, Buck-
inghamshire, and Oxfordshire ; and in all these districts they
are oxidised carbonates. Brown haematites also are among
the most important of the ores smelted in France and Ger-
many. " Bog-iron-ore " is an impure brown haematite, smelted
in many localities. Associated with limonite, and included
under the name brown ores, are gothite (Fe 2 O d H 2 0) and
turgite (2Fe 2 3 H 2 0).

ANALYSES OF BROWN HAEMATITE IKON- ORES. *





A


B


C


D


E


F


Ferric oxide (Fe-jOs)


90-05


59*05


56-20


60-72


67-80


60-94


Manganous oxide
(MnO)


0-08


0-09


0-20




28




Alumina (AloOa)


0-14


trace


2-43)




10-19


8-03


Lime (CaO) ".


0-06


0-25


0-49 I


11-175


2-80


1-60


Magnesia (MgO)


0-20


0-28


0-17)




59


06


Silica (Si0 2 ) .


0-92


34-40


29-09


12-66


8-60


13-24


Phosphoric anhy














dride (P 2 5 )


0-09


0-14


0-84


trace





1-02


Sulphuric anhy-














dride (S0 3 )

















08


Sulphur


traces


\






0-075







Pyriets (FeS 2 )





0-09












Water (combined)
(hygroscopic)


9-22




6-141
0-24 /


10-90 |


13-77
1-60


} 15-35


15-35


Metallic iron per














cent. . . .


63-04


41-34


39-34


42-5


42-64


42-66



A. Forest of Dean (Dick). B. Glamorganshire (E. Riley). C.
Northamptonshire (Percy). D. New South Wales. E. Antrim.
F. Lincolnshire .

As previously mentioned, brown haematites vary much,
both as regards the percentage of metallic iron which they



ORES OF IRON. 31

contain, and also in their freedom from such impurities as
phosphorus and sulphur, whilst manganese is almost always
present in those ores, and they are accompanied by more
or less earthy matter.

Titaniferous iron-ore, or Ilmenite, occurs massive, but
is found generally as a dark-coloured or black sand along
the shores of the Bay of Naples, the North-east coast of
America, Labrador, New Zealand, etc. Certain ferruginous
crystalline rocks having been disintegrated, the lighter
portions are washed away, whilst the heavier titaniferous
particles, or grains, constituting the bluish iron sands, accumu-
late upon the shore in sufficient quantity to be collected,
and, after a preliminary mechanical treatment, to be smelted
for the production of iron. The titaniferous sands contain
a large proportion of magnetite, besides titaniferous iron-
ore, and these are usually accompanied by free silica, with
more or less magnesia. Titaniferous iron-ore is a most
refractory mineral, and when in a fine State of division is
difficult to treat in the blast furnace.

Carbonate Ores. Ferrous carbonate, FeC0 3 , is abundant
as an iron mineral, and in admixture with various foreign
matters forms valuable ores of iron.

The purer varieties are described as spathic ores, whilst
the amorphous argillaceous ores of the Coal Measures are
known as clay ironstones, and when largely impregnated
with carbonaceous or bituminous mattsr they constitute
blackband ironstone.

Spathic Ore. Spathic ore in its purest form constitutes
the crystallised mineral known as siderite, which, when pure,
yields 48*27 per cent, of metallic iron. Siderite occurs as a
mineral having a pearly lustre, and varying from yellow to
brown in colour, but when it occurs in veins exposed to water
and atmsopheric influences, it is usually found to have suffered
decomposition, and to have become converted into brown
haematite to a considerable depth from the surface. Spathic ores
often contain considerable quantities of manganous oxide, as is
the case with the spathic ore of the Brendon Hills, in Somer-
setshire, which was at one time transported to Ebbw Vale,
South Wales, to be smelted for the production of the
manganiferous pig-iron known as spiegeleisen The other
more important associates of spathic ores are calcium and



32



IRON.



magnesium carbonates, with occasionally also quartz, with
copper and lead in small proportion. This ore occurs in
the Carboniferous rocks of Durham, Cornwall, Devon, and
Somersetshire, but more largely on the Continent, as in the
mountain masses of Siegen and Musen, in Rhenish Prussia,
where it is found in rocks of Devonian age ; at Thuringia,
in Hungary, it occurs in Permian rocks ; whilst extensive
deposits also are present in Styria, Westphalia, Lolling, and
Carinthia, in Austria, as also in Hanover and in Russia.

ANALYSES OF SPATHIC AND OTHER IRON ORES.





A


B


C


D


Ferrous oxide (FeO) .


43-84


45-86


40-77


39-92


Ferric oxide (Fe-jOa) .


0-81


0-40


2-72


3-60


Carbonic anhydride (C0._>) .


38-86


31-02


26-41


22-85


Manganous oxide (MnO)


12-64


0-96





0-95


Alumina (ALOa)





5-86





7-86


Lime (CaO) . "...


0-28


1-37


0-90


7-44


Magnesia (MgO) . - .


3-63


1-85


0-72


3-82


Potash (K,0) . .











0-27


Silica and insoluble residue


0-08


10-68





8-76


Clay








10-10





Phosphoric anhydride (PjjOa)





0-21





1-86


Pyrites (FeS.,) .





o-io





0-11


Water (OH 2 )" . ,, ; . ,-


0-18


1-08


i-oo


2-97


Organic matter . . . -





0-90


17-38







100-32


100-29


100-00


100-41,


Metallic iron per cent. .:


34-67


35-99


33-57


33-62



A. Spathic ore, from Somersetshire (Spiller). B. Clay ironstone
from Dudley (Dick). C. Blackband, Scotland (Colquhoun). D.
Cleveland Ironstone (Dick).

Clay ironstone is the argillaceous, amorphous, compact,
or earthy variety of ferrous carbonate, occurring either in
detached nodules, or in layers of nodular concretions, dis-
tributed through the shales and clays of the Coal Measures,
or in beds 01 considerable thickness in Liassic rocks. These
consist of ferrous carbonate mixed with a considerable quantity
of clayey matter, or perhaps rather are beds of clay which
have become saturated with carbonate of iron. The iron may
be evenly distributed through the bed, or it may be collected
into concretionary masses. When not discoloured by



OliES OF IRON. 33

admixture with carbonaceous matters or by atmospheric de-
composition, they range in colour from light grey or yellow
to brown, but the lighter coloured varieties rapidly become
brown on exposure to the atmosphere ; they are always
impure, containing in addition to the clay appreciable
quantities of calcium, magnesium, and manganese carbon-
ates, phosphoric acid, iron pyrites (FeS 2 ), and occasionally
also other minerals, as blende (ZnS) and galena (PbS). The
principal localities in which they occur are the Coal Measures
of North and South Staffordshire, Derbyshire, Yorkshire,
Warwickshire, Shropshire, North and South Wales, Den-
bighshire, and in Scotland.

Blackband ironstone is ferrous carbonate associated with
from 15 to 25 per cent, of bituminous, coaly, or other carbon-
aceous matter, which gives it almost the appearance of coal
it is, in fact, a bed of coal which has become saturated with
ferrous carbonate ; it occurs in beds most largely in the
coalfields of Lanarkshire and Linlithgowshire, to a smaller
extent in North Staffordshire, and also in South Wales.
Owing to the large amount of carbonaceous matter contained
in this ore, it can be calcined in heaps without the addition
of any further fuel, and the calcined product yields from
50 to 60 per cent, of metallic iron.

Other earthy and metallic impurities are always present,
and the ore always contains a considerable quantity of phos-
phorus. Black band ores were discovered in Scotland by
Mushet, in 1801, and when the hot blast was introduced they
came rapidly into use and " made " the Scotch iron industry.
The Scotch deposits are now almost exhausted.

Cleveland Ironstone. This is one of the most important
ores now raised in this country. It was first worked about
1850, and it has led to the development of Middlesbrough
into the most important iron-producing district in the country.
It is an impure carbonate, the carbonate being associated with
calcium carbonate and other earthy matters. The beds
seem to be beds of an oolitic limestone in which the calcium
carbonate has been replaced by ferrous carbonate. The beds
belong to the Liassic series. They are very fossiliferous,
the two main beds being distinguished by the names of
the predominant fossils, the Avicula and Pecten beds. The
total thickness of the beds is about 15 ft. The mines are on



34 IRON.

the Cleveland Hills, a few miles behind that is, south of
Middlesbrough so that the ore can easily be brought down
to the town.

The ore is more or less granular or oolitic in structure, and
usually of pale bluish-green colour, due to the presence of
ferrous silicate ; but some varieties are darker. One bed at
Rosedale Abbey, now exhausted, was very dark nearly black
and was magnetic from the presence of magnetic oxide.
One of the most important characters of the ore is the large
quantity of phosphorus always present, owing to the very fos-
siliferous character of the rock. Ores very similar in character
to those of Cleveland are now being worked in other places.
The readiness with which the carbonate passes into the hydrate
under the influence of air and moisture has already been ex-
plained, and in many cases where surface deposits of brown
ore have been worked through, carbonate has been found
underlying. This has been the case in Northamptonshire.
In Lincolnshire extensive beds of fossiliferous carbonates of
the Lias age are now being worked, and an extensive iron
industry is growing up there in consequence. The ores are
high in phosphorus, yellow and green in colour, and are not
unlike those of Cleveland. The workable beds are about 16 ft.
in thickness

Imported Iron Ores. With the introduction of the Bes-
semer process for steel-making there arose a great demand
for pig iron free from sulphur and phosphorus, and this could
only be made from ores free from these elements. As the
only British deposits of suitable material those of North
Lancashire and Cumberland were quite inadequate to meet
the demand, ironmasters had to seek other sources of supply.
The enormous development of the iron industry during tin;
last thirty or forty years has also necessitated a supply of
ore greater than the home mines could yield, so that the world
has been searched for suitable ore deposits, and an immense
import trade in iron ore has grown up.

Among the most important of the districts supplying iron
ore is Bilbao, in Spain, from which district about 8,000,000
tons of ore is annually exported. The ores are red and brown
haematites and carbonates, the brown ore being due to surface
oxidation of the deeper-lying carbonate. Four varieties of
ore may be mentioned :



ORES OF IRON.



35



(1) Vena. A dark purple ore, very soft, and yielding about
60 per cent, of iron. It occurs only in small quantity.

(2) Campanil. A dark red ore, yielding about 55 per cent,
of iron, the gangue being mainly carbonate of lime. This ore
has been largely used both for smelting and in the open-
hearth steel furnace, but the supply is now nearly exhausted.

(3) Rubio. A brown or yellow ore occurring in lumps
which often have a vesicular structure. Being a brown ore,
it contains a considerable quantity of water, and yields about
50 per cent, of iron. The gangue is siliceous.

(4) The carbonate ore is now being largely worked. It
has an oolitic structure, and is always calcined before export.

All these ores are free from sulphur and phosphorus. Iron
ores occur, and are extensively worked, in many other parts of
Spain : Carthagena, Almeira, Sevilla, Huelva, and other locali-
ties may be mentioned. The ores are sometimes black (mag-
netites), more often red (haematites), but generally brown ores,
and they are usually free from sulphur and phosphorus.
Iron ores are also imported from Canada, from Cuba, from
Norway and Sweden, from Elba, and many other localities.
Imported ores are not now always phosphorus -free, as for
some purposes there is a demand for phosphoric ores.

The following analyses will give an idea of the character of
the imported ores :





A


B


C


D


E


F


Iron


58-80


55-49


68-50


48-26


58-61


46-56


Manganese


1-47


70


Trace


3'51





1-82


Silica


3-20


8-88


2-50


7-00


5-42


3-08


Lime


4'60


Trace





2-44





8-22


Sulphur





012


040


017


276


046


Phosphorus


Trace


012


018


014


017


016


Copper

















019


Moisture


6-00*


10-30


Trace


2'50


1-50


6-50



A. Campanil. B. Rubio. C. Gellivara. D. Almeira, Spain.
E. Mokla, Algeria. F. Seriphos, Greece.

* And carbon dioxide.



Output and Consumption of Ore in the United Kingdom.
In order that the student may understand to what extent
Great Britain is at present dependent on foreign ore supply



36 IRON.

and the wide field from which this is derived, the following
figures for the year 1904 are given :

The total amount of iron ore raised in Great Britain was
13,774,282 tons, of which the output was from :

TONS.

Cleveland 5,758,510

Scotland 838,104

Staffordshire . 818,468

The ore imported, including chrome ore, was from :

TONS.

Sweden 238,256

Norway 281,862

Germany ........ 2,534

Holland 11,450

Belgium 9,410

France 172,050

Portugal . 6,045

Spain i - . . 4,648,355

Italy

Greece . . -..'... .. - ... .. . 344,555

Turkey, European 6,961

Turkey, Asiatic . . . ; ' * ''";-' . . 2,802

Algeria . . ''.'" . . . - : ~ \ , 237,744

Persia . .",-./ . / .-:;-..'.:.'. 2,441

United States . . . . ... 5,317

Other Foreign Countries . < . ... 79,145

Total from Foreign Countries ,. .- .. . 6,649,807

From British Possessions :

Australia :

Victoria 78

New South Wales 4,115

Canada . . . - , -.' . . . . 22,290

Newfoundland . . . . . . 18,217

Other British Possessions ' 6,429



Total from British Possessions . . . . 51,129

Total imports from all sources, 6,700,746 tons, or, roughly
speaking, of the total ore used about one-third is imported.
If it were measured by the amount of iron produced the pro-
portion would Be much larger, since the imported ores are
in general much richer in iron than those raised at home.

In the year 1904 the amount of manganese ore imported



ORES OF IRON 37

was 205,175 tons, of which 95,840 tons came from Russia ,
52,620 tons from Brazil, and 27,970 tons from India, whilst onl>
3,971 tons came from Greece.

American Iron Ores. The immense development of the
American iron industry during the last twenty-five years has
been largely due to the discovery of immense deposits of rich
and easily- worked iron ores. Iron ores of all kinds are widely
distributed in the United States, but, as a rule, only the richer
varieties, such as magnetites and red and brown ores are
smelted. The most important ores at present worked are the
haematites of the Lake Superior District, about 75 per cent,
of the iron made in the United States being made from these
ores. The ores come to the surface in thick beds, and are
often worked by quarrying, steam navvies being largely em-
ployed to lift the ore and transfer it to the railway ^trucks.

In the year 1903 the output in the Lake Superior district
was :

TONS.

From the Marquette Range . . . . . 3,040,245

Menominee . .. ^ "' ' . 3,749,567

Gogebic . . .'" . 2,912,912

Vermillion . / . . 1,674,699

Mesabi . . ^ . . 12,892,542

Total .... . . 24,271,965

the total output of the United States for the year being
32,471,550 tons. The ores are low in sulphur and phosphorus,
and the iron is made of the Bessemer or Haematite quality. In
the Southern States haematite ores occur which contain phos-
phorus, and are therefore used in the manufacture of foundry

pig-
Classification of Iron Ores. Iron ores may be classified
in various ways. A convenient classification is that based
on the mineral which forms the basis of the ore :

Black ores contain Magnetite.
Red ores Haematite.

Brown ores ,, Limonite.

Carbonate ores ,, Carbonate.

For practical purposes ores are often classified into non-
phosphoric and phosphoric. Non-phosphoric ores are such



38 IRON.

as contain less than '06 per cent, of phosphoric anhydride,
such as the Cumberland and North Lancashire Haematites,
Bilbao ores, etc. Phosphoric ores contain more than '60
per cent, of phosphoric anhydride, such as Cleveland ores,
Blackland ores, Clayband ores, etc:" Or they may be classified
according to the nature of the gangue associated with the
iron mineral :

(1) Siliceous Ores. Those in which the gangue is mainly
silica e.g. the Cumberland, North Lancashire Haematites,
most Spanish ores, etc.

(2) Calcareous Ores. In which the gangue is mainly car-
bonate of lime e.g. Campanil ore.

(3) Aluminous Ores. In which the gangue is mainly
alumina e.g. Belfast aluminous ore.

(4) Argillaceous Ores. Those in which the gangue is
mainly clay e.g. Clayband ores.

(5) Bituminous Ores. Those in which the gangue con-
tains a large quantity of bituminous or coaly matter e.g.
Blackband ores.

This classification is very convenient for smelting
purposes.






39



CHAPTER IV;

METALLURGICAL CHEMISTRY OF IRON.

PURE metallic iron, as already stated, is a body difficult of
preparation, especially in the compact state, except by
laboratory methods, and the pure metal is not therefore a
substance of commercial importance ; but in combination
with variable but small proportions of carbon, and other
metallic and non-metallic elements, such as sulphur, silicon,
phosphorus, manganese, etc., it constitutes the various
qualities of pig-iron, steel, and malleable-iron. The chemical
symbol for iron is Fe, and its atomic weight is 56.

Pure iron is prepared by the electrolysis of ferrous chloride
(FeCL,), by the reduction of ferric oxide (Fe.>0 3 ), or of ferrous
chloride, by heating either of them to redness in a tube
through which a current of hydrogen gas is passed ; or in
a nearly pure state it can be obtained by the fusion under
a layer of glass free from metallic oxides, of fine iron wire
or iron filings, with artificially-prepared magnetic oxide of
iron. Iron as prepared by the last method is a metal vary-
ing in colour from bluish-grey to silver whiteness according
to the state of its aggregation ; as reduced from ferric oxide
by hydrogen, it forms a grey powder, which is pyrophoric
(that is, takes fire spontaneously on exposure to the atmo-
sphere) if the temperature employed in its production has
not exceeded dull redness ; but it no longer possesses this
quality if the temperature employed in its preparation has
exceeded this limit. As obtained from ferrous chloride
(FeCl 2 ), the metal yields well-defined cubical crystals, and it
is always crystalline after fusion. Iron is capable of receiving
a high polish, it is very tenacious, ductile, and malleable,
the last quality being unaffected by heating and subse
quent rapid cooling, neither is it hardened by this treatment;
Electro-deposited iron absorbs or occludes hydrogen to the
extent of from seventeen to twenty times its own volume.



40 IRON.

Magnetism of Iron. One of the most striking properties
of iron, in which it excels all other elements, is its power of
becoming magnetic. If a piece of nearly pure iron be brought
into a magnetic field, it at once becomes magnetic to a much
higher degree than the field in which it is placed. Its mag-
netic permeability is therefore said to be high. It seems to
concentrate the surrounding magnetism into itself. Imme-
diately it is taken out of the magnetic field the magnetic power
is lost that is, it is not retained by the iron, or its magnetic
retentivity is almost nil. At a high temperature about a
red heat the magnetic permeability is completely lost, and
the iron ceases to be magnetic. The presence of foreign
elements in the metal greatly modifies its magnetic proper-
ties. A small percentage of carbon decreases the permeability,
but increases the retentivity, so that permanent steel magnets
can be made, whilst a considerable percentage of manganese
destroys both properties.

Pure iron is softer than the commercial varieties of malle-
able iron, and has a specific gravity of 7'87. Its melting point
does not appear to have been accurately determined, for whilst
Pouillet estimates it at from 1,500 C. to 1,600 C. (2,732 F.
to 2,912 P.), Scheerer gives it as 2,100 C. (3,812 P.), but
the presence of small quantities of carbon in combination
with the metal rapidly lowers the melting point.

Iron is unaffected by dry air at ordinary temperatures
(except in the pyrophoric or spongy state already described),
or in perfectly pure water free from air, oxygen, or. carbonic
anhydride ; but if exposed to a moist atmosphere, then the
oxidation commonly known as rusting rapidly proceeds,
if carbon-dioxide is also present, as it always is, in the
atmosphere. The presence of carbon-dioxide appears
essential to the rusting of the iron by moisture, since the
metal may be kept bright for almost any length of time
in pure lime water, or in a solution of soda. Under the
joint influence of moisture, oxygen, and carbon-dioxide,
ferrous carbonate is first produced on the surface of
the iron, but this, by absorbing a further proportion of
water and oxygen, becomes changed to a hydrated ferric
oxide, with the liberation of carbon-dioxide, which latter
then reacts upon a fresh portion of the iron in the presence
of water and oxygen, and a further quantity of ferrous car-






METALLURGICAL CHEMISTRY OF IRON. 41

bonate is produced, and so the cycle continues to be repeated.
Further, the hydrated oxide, or rust, is electro-negative
with respect to the metallic iron upon which it is formed,
and the electrical condition thus resulting still further pro-
motes the action of oxygen on the metal, and the corrosion
of the , iron thus proceeds rapidly. Water holding carbon
anhydride and free oxygen in solution rapidly attacks and
oxidises metallic iron. Iron, when heated to redness in
contact with air or oxygen, is rapidly oxidised, with the pro-
duction of a black scaly oxide readily detachable from the
surface of the iron. This oxide constitutes, on the large scale,
the hammer-scale or hammer-slag of the forge, and is mainly
the magnetic oxide Fe 3 4 . Iron at a red heat decomposes
water with the liberation of hydrogen and the formation of
Fe, ( 4 .

Hydrochloric acid attacks metallic iron with the forma-
tion of ferrous chloride (FeGL>) and the liberation of free
hydrogen. Concentrated sulphuric acid (IL>S0 4 ) also attacks
the metal with the liberation of sulphur-dioxide (S0. 2 ),


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