Chemical elements
    History of Iron
    Physical Properties
      Occlusion of Gases
      Absorption of Nascent Hydrogen
      Permeability to Gases
      Passivity of Iron
      Iron Powder
      Iron sponge
      Iron amalgam
      Colloidal Iron
      Pyrophoric Iron
      Iron Ions
      Atomic Weight
    Chemical Properties
    Iron Salts
    PDB 101m-1aeb
    PDB 1aed-1awd
    PDB 1awp-1beq
    PDB 1bes-1c53
    PDB 1c6o-1ci6
    PDB 1cie-1cry
    PDB 1csu-1dfx
    PDB 1dgb-1dry
    PDB 1ds1-1e08
    PDB 1e0z-1ehj
    PDB 1ehk-1f5o
    PDB 1f5p-1fnp
    PDB 1fnq-1fzi
    PDB 1g08-1gnl
    PDB 1gnt-1h43
    PDB 1h44-1hdb
    PDB 1hds-1i5u
    PDB 1i6d-1iwh
    PDB 1iwi-1jgx
    PDB 1jgy-1k2o
    PDB 1k2r-1kw6
    PDB 1kw8-1lj0
    PDB 1lj1-1m2m
    PDB 1m34-1mko
    PDB 1mkq-1mun
    PDB 1muy-1n9x
    PDB 1naz-1nx4
    PDB 1nx7-1ofe
    PDB 1off-1p3t
    PDB 1p3u-1pmb
    PDB 1po3-1qmq
    PDB 1qn0-1ra0
    PDB 1ra5-1rxg
    PDB 1ry5-1smi
    PDB 1smj-1t71
    PDB 1t85-1u8v
    PDB 1u9m-1uyu
    PDB 1uzr-1vxf
    PDB 1vxg-1wri
    PDB 1wtf-1xlq
    PDB 1xm8-1y4r
    PDB 1y4t-1ygd
    PDB 1yge-1z01
    PDB 1z02-2a9e
    PDB 2aa1-2azq
    PDB 2b0z-2boz
    PDB 2bpb-2ca3
    PDB 2ca4-2cz7
    PDB 2czs-2dyr
    PDB 2dys-2ewk
    PDB 2ewu-2fwl
    PDB 2fwt-2gl3
    PDB 2gln-2hhb
    PDB 2hhd-2ibn
    PDB 2ibz-2jb8
    PDB 2jbl-2mgh
    PDB 2mgi-2o01
    PDB 2o08-2ozy
    PDB 2p0b-2q0i
    PDB 2q0j-2r1h
    PDB 2r1k-2spm
    PDB 2spn-2vbd
    PDB 2vbp-2vzb
    PDB 2vzm-2wiv
    PDB 2wiy-2xj5
    PDB 2xj6-2ylj
    PDB 2yrs-2zon
    PDB 2zoo-3a17
    PDB 3a18-3aes
    PDB 3aet-3bnd
    PDB 3bne-3cir
    PDB 3ciu-3dax
    PDB 3dbg-3e1p
    PDB 3e1q-3eh4
    PDB 3eh5-3fll
    PDB 3fm1-3gas
    PDB 3gb4-3h57
    PDB 3h58-3hrw
    PDB 3hsn-3ir6
    PDB 3ir7-3k9y
    PDB 3k9z-3l4p
    PDB 3l61-3lxi
    PDB 3lyq-3mm8
    PDB 3mm9-3n62
    PDB 3n63-3nlo
    PDB 3nlp-3o0f
    PDB 3o0r-3p6o
    PDB 3p6p-3prq
    PDB 3prr-3sel
    PDB 3sik-3una
    PDB 3unc-4blc
    PDB 4cat-4erg
    PDB 4erm-4nse
    PDB 4pah-8cat
    PDB 8cpp-9nse

Physical Properties of Pure Compact Iron

The properties of iron are affected to such a remarkable and unique extent by the presence of small quantities of alloying elements, chief amongst which is carbon, that these phenomena are an important study in themselves. It is not intended in this section, therefore, to deal with the physical properties of any commercial iron other than the chemically pure and compact metal. For a discussion of the physical and metallurgical properties of various types of commercial iron and its alloys. Pure iron is a white metal which can be readily machined in a lathe, and even cut with a knife. It crystallises according to the cubic system, but crystals are rare, the metal being usually massive. Dendritic crystals may be obtained artificially with branches parallel to the cubic axes. Shock apparently assists or induces crystallisation in iron.

Pure iron, prepared by reducing ferrous chloride with hydrogen at temperatures up to about 800° C., usually separates in small hexahedra, although it sometimes yields rhombic dodecahedra and tetrakishexahedra. The mechanical properties of the individual crystals of iron vary with the crystallographic orientation. For example, the metal is brittle in the direction of the planes of cleavage, but exhibits considerable plasticity in other directions. In compact iron the crystals are separated from each other by an amorphous cement, which acts as a binding agent. The metal is ductile and malleable. It possesses considerable tenacity, a wire 2 mm. in diameter being capable of supporting 250 kgms. This value is greatly influenced by the presence of alloying elements, particularly carbon.

At a low temperature, such as that of liquid air, pure iron is very brittle; indeed most alloys of iron, with the exception of those containing nickel, lose in ductility as the temperature falls.

The density of the metal varies somewhat according to its mechanical history, the usual values obtained for the pure metal ranging from 7.85 to 7.88.

As a rule the density of a metal decreases with cold working, and iron appears to be no exception. Iron filings are less dense than the compact metal from which they are obtained, as indicated by the following data: -

Pure compact iron7.8558
Filings from ditto7.8172
Decrease in density0.0886

The effect of cold-drawing of wire upon the density of the metal is clearly shown by the following data, obtained with iron piano-wire. The density has been calculated for a vacuum at 4° C.

Mean Density.
Piano-wire annealed7.7970
Piano-wire cold drawn7.7772
Decrease in density0.0198

Upon annealing the density tends to return to its original value.

The density of solid iron near its melting-point is 6.95, whilst that of the liquid metal a few degrees higher in temperature is 6.88.

Addition of carbon effects a reduction in the density of the metal. The melting-point of iron has frequently been determined; the most reliable results are between 1505 and 1533.

According to Knocke, the volatilisation of iron in vacuo is sufficiently great to be detected at 755° C, The metal boils at 2450° C. ±50° C. at 36 mm. pressure.

Moissan succeeded in volatilising iron in his electric furnace with a current of 350 amperes at 70 volts. In a few minutes a sublimate or distillate of iron was obtained on a water-cooled tube as a grey powder mixed with some brilliant and malleable scales, and possessed of the same chemical properties as the finely divided metal. The distillation of iron in this manner is difficult on account of the violent frothing caused by the boiling metal evolving occluded gases.

The specific heat of iron rises with the temperature.

The following values for the specific heat of a sample of pure iron (Fe 99.87 per cent.) for temperatures ranging from 0° to 100° C. are given by Griffiths, the extreme temperature ranges being 1.4° C.: -

Temperature.°C.Specific Heat.

For intermediate temperatures, the specific heat (S$) may be calculated from the equation

St = 0.1045 (1 + 0.001520t — 0.00000617t2).

Other recent results are: -

Temperature Interval. °C.Specific Heat.
17 to 1000.10983
17 to 1000.1098
-188 to + 200.0859
-185 to + 200.095

There is marked discontinuity above 900° C.

The specific heat of iron appears to be very slightly increased by cold working.

The coefficient of linear expansion of iron with rise of temperature has been determined for a pure iron containing

Carbon0.057 %
Manganese0.13 %
Silicon0.05 %

The results are as follow: -

Temperature Interval.°C.Total Expansion per Unit Length.Coefficient of Expansion per 1° C.
0 to 1000.00110.000011
0 to 2000.00230.0000115
0 to 3000.00360.000012
0 to 4000.00500.0000125
0 to 5000.00650.000013
0 to 6000.00810.0000135
0 to 7000.009750.000014
0 to 8000.011250.000014

When heated to 950° C. in an inert atmosphere, iron is disintegrated, emitting particles at right angles to its surface and assuming an etched appearance.

Refractive index of Iron

The refractive index of iron, for sodium light, is 1.85.

The most intense lines in the spectrum of iron are as follow: -

Arc: 3020.75, 3021.19, 3047.72, 3440.77, 3441.13, 3466.02, 3490.73, 3565.54, 3570.24, 3570.29, 3581.34, 3581.38, 3609.01, 3618.91, 3631.60, 3648.00, 3705.74, 3708.06, 3709.39, 3720.09, 3722.73, 3735.02, 3737.30, 3745.70, 3748.40, 3749.62, 3763.92, 3763.99, 3816.00, 3820.61, 3824.60, 3826.07, 3828.00, 3834.40, 3860.03, 3886.45, 4045 .99, 4063.74, 4063.77, 4071.92, 4260.68, 4271.95, 4308.09, 4325.97, 4383.71, 4404.95, 4415.31, 5167.67, 5233.15, 5269.70, 5324.38, 5365.00, 5367.61, 5370.13, 5383.58, 5404.34, 5411.15, 5415.40, 5424.30, 5429.94, 5445.28, 5447.15, 5455.81, 5573.09, 5586.98, 5615.89, 6400.25, 6495.25.

Spark: 2599.50, 2739.63, 2749.41, 2755.80, 4045.99, 4308.10, 4325.97, 4383.73, 4404.95.
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