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

Properties of Iron Powder

Iron powder, as obtained by the reduction of ferrous or ferric salts, is considerably more chemically reactive than the compact metal. Thus, the powder obtained by reduction of iron oxide, carbonate, or oxalate in a current of hydrogen at 440° C. is pyrophoric, becoming incandescent upon exposure to moist air. It decomposes acetylene with incandescence, depositing free carbon and yielding small quantities of benzene. Reduced iron absorbs some 2 per cent, of nitrogen at atmospheric temperature, the solubility of the gas being proportional to the square root of the pressure. According to Sieverts, Kahlbaum's reduced iron absorbs nitrogen at 900° C., and this is quantitatively released on cooling.

When maintained at 310° to 320° C. for about forty-eight hours, pyrophoric iron is transformed into the non-pyrophoric form, the change being accompanied by an increase in volume. Probably the pyrophoric form consists of a mixture of molecules of different kinds which are not in a state of equilibrium.

Nitrogen peroxide is decomposed by reduced iron at the ordinary temperature, the metal becoming incandescent and yielding a mass of ferric oxide, Fe2O3. Nitrous oxide is reduced at 170° C., and nitric oxide at 200° C., ferrous oxide resulting.

Nitric oxide is almost quantitatively converted into ammonia when mixed with hydrogen and passed over the warmed metal. The reaction begins at about 300° C., and is very rapid at 350° C.

When heated in a continuous current of carbon monoxide at 650° C., a considerable quantity of carbon is deposited. If, however, the carbon monoxide is admitted to a closed vessel containing the heated metal, absorption of the gas takes place, possibly with the formation of cementite - that is, iron carbide, Fe3C.

In contact with air and water iron powder readily rusts at ordinary temperature. When warmed with water, hydrogen gas is evolved. Dilute solutions of sodium and potassium hydroxides are decomposed at their boiling-points in a similar manner. Under the influence of gentle heat iron powder decomposes steam - a reaction that has been recommended as a most convenient one for rapidly obtaining small quantities of pure hydrogen. The gas is evolved at considerably lower temperatures than when compact iron is used, decomposition proceeding slowly, in the presence of Kahlbaum's reduced iron, at about 250° C.

Finely divided iron decomposes sulphuric acid of density 1.75 at 200° C., yielding sulphur dioxide.

It is spontaneously inflammable in sulphur vapour, the ignition temperature lying below 448° C.

The exceptionally pure reduced metal obtained by Lambert and Thomson possessed several unusual properties. Thus, it exhibited remarkable inertness or " passivity," remaining free from rust upon prolonged exposure to air and tapwater.

Cold, dilute sulphuric and nitric acids had very little action on the metal, but on warming the iron readily dissolved. Aqueous hydrogen chloride attacked the metal even in the cold. Saturated solutions of the sulphate or nitrate of copper exerted no action at ordinary temperatures; even after an exposure of several months to copper sulphate solution, no change could be detected in the iron when examined under the microscope. On raising to 100° C., however, the iron gradually dissolved, copper being simultaneously deposited.

Solutions of copper chloride, when concentrated, immediately attacked the metal, depositing copper. Even dilute solutions (less than one per cent.) attacked the iron, although slowly.

Copper was also deposited on the metal if the latter was subjected to pressure in an agate mortar prior to being placed in the copper sulphate solution. Pressure with a quartz rod whilst immersed in the solution had a like effect.

These remarkable results might be attributed to a film of hydrogen protecting the metal in the first experiments from attack in copper sulphate solution, the film being disrupted in the later experiments by the pressure; but specimens of the metal which had been heated for several hours at 1000° C. in a vacuum, until spectroscopic tests showed that all hydrogen had been removed, behaved in precisely the same manner.

When the pure metal was treated with ferroxyl, unlike ordinary iron, it remained quite bright for an indefinite time, manifesting no tendency to corrode. On applying pressure locally, however, corrosion set in, a pink colour developing round the pressed portion, and Turnbull's blue appearing round the unpressed parts, indicating solution of the metal.

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