Fe3O4 question
Your Actual Name
biom...@wimsey.com (Brad Brush) writes: > We have come upon a chemical that we cannot explain at our school. It is
> called Iron ferrosferric (natural magnetite), formula Fe3O4, one of the iron
> oxides.
>
> The combining capacity of oxgyen is almost always -2 (except for peroxides).
> Iron has a capacity of 2 or 3. This does not come out to be a ratio with intact
> integers. How can I explain this?
> Thanks.
>
> Brad Brush
> McRobert's Secondary
> Richmond BC Canada
You are almost always correct in saying that oxygen can be counted as a
-2. It works just fine in this case. As for iron, this is a mixed
system. Two of the iron atoms can be considered as having a formal +3
(ferric, Fe3+) charge and the remaining iron atom has a formal +2
(ferrous, Fe2+) charge. (sum of +8, charge is conserved and the crystal
does not explode) Remember, this assignment of charge is just a model.
The actual charges assigned by a more sophisticated quantum mechanical
(ab initio) model would show far more delocaliztion. However, the mixed
states explanation holds well for high school chemistry.
-infinite resistor
Brad Brush
Alan "Uncle Al" Schwartz
biom...@wimsey.com (Brad Brush) wrote:
>We have come upon a chemical that we cannot explain at our school. It is
>called Iron ferrosferric (natural magnetite), formula Fe3O4, one of the iron
>oxides.
>
>The combining capacity of oxgyen is almost always -2 (except for peroxides).
>Iron has a capacity of 2 or 3. This does not come out to be a ratio with intact
>integers. How can I explain this?
If you are clever, the "rules" are hardly more than guidelines. Consider
Ni3Al (which forms in a brobdingnagian exotherm from the constituent
mixed powders plus a spark) or Zintl ions. The Taube-Creutz ion and
congeners are lovely. Consider silicon monoxide used for optics
coatings, intersitial carbides used as ultrahard and refractory
materials, and most of closo-, nido-, etc. borane chemistry.
FeO.Fe2O3 has an unusual structure. It is the classic example of
ferrites (hey, add perovskites and spinels!) used in ceramic magnets,
catalysts (copper chromite), clever electronic components (barium
titanate, PZT), high temp ceramic superconductors (YBa2Cu3O5,
non-stoichiometric in oxygen)... This is important stuff. Stainless
steel is stainelss because on its surface it forms a complex and
chemically resistant chromium oxide. Black titanium suboxides are
incredibly chemically inert - and are excellent electrical conductors!
Chemistry is structure as well as stoichiometry. Potassium oxide is K2O.
Potassum superoxide is KO2, and it is yellow and paramagnetic, and a
reducing agent. KO2 also exists, potassium eproxide. So does KO3,
potassium ozonide. O2+PF6- lead Neil Bartlett in 1962 to make the first
chemical compound of xenon, XePtF6.
(BTW, everybody has been lying to you. Take a globe of the Earth. Make
a segment of the equator one side of a triangle. Make the North Pole one
vertex. Make any two lines of longitude the other two sides. Add up the
sum of the interior angles of the triangles. It's more than 180 degrees
no matter how you slice it. Euclid is incomplete.)
--
Alan "Uncle Al" Schwartz
Uncl...@ix.netcom.com ("zero" before @)
http://www.ultra.net.au/~wisby/uncleal.htm
(Toxic URL! Unsafe for children, Democrats, and most mammals)
"Quis custodiet ipsos custodes?" The Net!
Eric Lucas
Your Actual Name <your...@ppg.com> wrote in article
<5auadb$h...@news.ppg.com>...
> biom...@wimsey.com (Brad Brush) writes: > We have come upon a chemical
that we cannot explain at our school. It is
> > called Iron ferrosferric (natural magnetite), formula Fe3O4, one of the
iron
> > oxides.
> >
> > The combining capacity of oxgyen is almost always -2 (except for
peroxides).
> > Iron has a capacity of 2 or 3. This does not come out to be a ratio
with intact
> > integers. How can I explain this?
> > Thanks.
> >
> You are almost always correct in saying that oxygen can be counted as a
> -2. It works just fine in this case. As for iron, this is a mixed
> system. Two of the iron atoms can be considered as having a formal +3
> (ferric, Fe3+) charge and the remaining iron atom has a formal +2
> (ferrous, Fe2+) charge. (sum of +8, charge is conserved and the crystal
> does not explode) Remember, this assignment of charge is just a model.
> The actual charges assigned by a more sophisticated quantum mechanical
> (ab initio) model would show far more delocaliztion. However, the mixed
> states explanation holds well for high school chemistry.
In fact, I think I remember seeing the crystal structure for this material
once, and it had two different Fe sites in the lattice in a 2:1 ratio, and
the geometries about these sites were consistent with the formal charge
assignments of 2 Fe(III) and 1 Fe(II). I guess I also thought that, unless
there are Fe-Fe bonds (which I don't think there were), that spin
delocalization through Fe-O-Fe interactions doesn't happen, and therefore
the unpaired spins are localized on Fe's that are formally Fe(III).
Can anyone verify?
Eric Lucas
Superdave the Wonderchemist
Brad Brush (biom...@wimsey.com) wrote:
: We have come upon a chemical that we cannot explain at our school. It is
: called Iron ferrosferric (natural magnetite), formula Fe3O4, one of the iron
: oxides.
: The combining capacity of oxgyen is almost always -2 (except for peroxides).
: Iron has a capacity of 2 or 3. This does not come out to be a ratio with intact
: integers. How can I explain this?
: Thanks.
: Brad Brush
: McRobert's Secondary
: Richmond BC Canada
As a simplification, think of it as a 1:1 mixture of FeO (Iron II) and
Fe2O3 (Iron III) packed into a crystal such that the net stoichiometry is
Fe3O4.
To go any further, you should probably ask a geochemist or geologist.
-Superdave The Wonderchemist
Ran Pan
It is possible for the existence of fractional valence. For Fe3O4, Fe is
8/3, and you can also regard Fe3O4 as a complex of FeO and Fe2O3, i.e.,
FeO.Fe2O3 where irons are 2 and 3 respectively.
Terry Ludwig
In article <5au3tl$f...@vanbc.wimsey.com> biom...@wimsey.com (Brad Brush) writes:
>From: biom...@wimsey.com (Brad Brush)
>Subject: Fe3O4 question
>Date: 7 Jan 1997 10:16:21 -0800
>We have come upon a chemical that we cannot explain at our school. It is
>called Iron ferrosferric (natural magnetite), formula Fe3O4, one of the iron
>oxides.
>The combining capacity of oxgyen is almost always -2 (except for peroxides).
>Iron has a capacity of 2 or 3. This does not come out to be a ratio with intact
>integers. How can I explain this?
>Thanks.
>Brad Brush
>McRobert's Secondary
>Richmond BC Canada
Fe3O4 is a combination of FeO and Fe2O3. Iron valences are +2 ("ous") and
+3 ("ic"), respecitvely. Oxygen valence is -2 in both cases.
Terry L.
Jeffrey Bodwin
On 7 Jan 1997, Alan "Uncle Al" Schwartz wrote:
{snip}
> (BTW, everybody has been lying to you. Take a globe of the Earth. Make
> a segment of the equator one side of a triangle. Make the North Pole one
> vertex. Make any two lines of longitude the other two sides. Add up the
> sum of the interior angles of the triangles. It's more than 180 degrees
> no matter how you slice it. Euclid is incomplete.)
>
reasoning is just wrong here. A triangle is a closed, three-sided planar
figure in which the sum of the interior angles is 180 degrees. The figure
you describe above is no more a triangle than my ass is a daisy. All three
sides of such a figure are curved and therefore the interior angles
wouldn't be expected to add up to 180 degrees.
Stick to the chemistry, Al.
-------------------------------**-------------------------------
| Jeffrey J. Bodwin Men look at love the same way they |
| bodw...@umich.edu look at smoke coming out of the |
| Just me, not you, not UM. front of their cars.-Tim Conlon |
~~~~~~~~~~**~~~~~~~~~**~~~~~~~~~**~~~~~~~~~**~~~~~~~~~**~~~~~~~~~~
Alan "Uncle Al" Schwartz
the North >>Pole one vertex. Make any two lines of longitude the other two sides. >>Add up the sum of the interior angles of the =
triangles. It's more >>than 180 degrees no matter how you slice it. Euclid is incomplete.)
>>
>What? Maybe I don't get the joke you're trying to make, but your line of
>reasoning is just wrong here. A triangle is a closed, three-sided planar
>figure in which the sum of the interior angles is 180 degrees. The figure
>you describe above is no more a triangle than my ass is a daisy. All three
>sides of such a figure are curved and therefore the interior angles
>wouldn't be expected to add up to 180 degrees.
>
>Stick to the chemistry, Al.
Learn some geometry, Jeff. A triangle consists of three points connected
by lines tracing the shortest distances between the three pairs of them.
1) Elliptical (Bolyai-Lobechevsky) geometry: No lines parallel to a
given line; all triangles' interior angles sum to >180 degrees. In the
special case of the surface of a sphere: geodesics, "straight lines," are
segments of great circles (the shortest distance between two points).
2) Plane (Euclidian) geometry: One line parallel to a given line; all
triangles' interior angles sum to 180 degrees exactly.
3) Hyperbolic (Riemannian) geometry: An infintie number of lines
lines are parallel to a given line; all triangles' interior angles sum to
<180 degrees.
See, they lied to you too.
BTW, the number of even integers is exactly equal to the sum of the
number of (even+odd) integers. Cantor had a lot to say about that. A
whole lot.
Don Wilkins
On Wed, 08 Jan 1997 01:50:19 GMT, k...@insync.net (Casey Donovan)
wrote:
>thw...@prairie.nodak.edu (Superdave the Wonderchemist) wrote:
>
>>Brad Brush (biom...@wimsey.com) wrote:
>>: We have come upon a chemical that we cannot explain at our school. It is
>>: called Iron ferrosferric (natural magnetite), formula Fe3O4, one of the iron
>>: oxides.
>>
>>: The combining capacity of oxgyen is almost always -2 (except for peroxides).
>>: Iron has a capacity of 2 or 3. This does not come out to be a ratio with intact
>>: integers. How can I explain this?
>>: Thanks.
>>
>>: Brad Brush
>>: McRobert's Secondary
>>: Richmond BC Canada
>>
>>
>>As a simplification, think of it as a 1:1 mixture of FeO (Iron II) and
>>Fe2O3 (Iron III) packed into a crystal such that the net stoichiometry is
>>Fe3O4.
>>
>>To go any further, you should probably ask a geochemist or geologist.
>>
>>-Superdave The Wonderchemist
>
>You might also ask a metallurgist. Magnetite is the oxide form
>(corrosion product) produced by steel in contact with severely
>limited amounts of moist atmospheric or dissolved oxygen. If not
>removed by some mechanical action, it forms an impervious thin
>layer on the metal surface. It's what keeps a steam boiler from
>quickly corroding into a pile of rust.
>
>BTW, it is magnetic, whereas Fe2O3 and (I think) FeO are not.
>This is a standard, though of course not definitive, test for its
>presence in a deposit.
>
Now let see if I have this straight. The gamma-Fe2O3 used in recording
tape is the figment of the manufacturers imagination.
Gamma-Fe2O3 is made by the oxidation of Fe3O4, retains the spinel
structure and is in fact magnetic. It changes to the non-magnetic
alpha-Fe2O3 at 600.
Nicht wahr
_ _ _ Für d' Flöh gibts a Pulver
(_| | |_/o | | | | o für d' Schuah gibts a Wix,
| | | | | | | _ _ , für'n Durst gibts a Wasser
| | | | |/ |/_) | / |/ | / \_ bloss fuer d' Dummheit gibts nix.
\_/ \_/ |_/|__/| \_/|_/ | |_/ \/
Jeffrey Bodwin
On 8 Jan 1997, Alan "Uncle Al" Schwartz wrote:
> >On 7 Jan 1997, Alan "Uncle Al" Schwartz wrote:
> >{snip}
> >> (BTW, everybody has been lying to you. Take a globe of the Earth.
>>Pole one vertex. Make any two lines of longitude the other two sides.
>>than 180 degrees no matter how you slice it. Euclid is incomplete.)
> >>
> given line; all triangles' interior angles sum to >180 degrees. In the
> special case of the surface of a sphere: geodesics, "straight lines," are
> segments of great circles (the shortest distance between two points).
>
> 2) Plane (Euclidian) geometry: One line parallel to a given line; all
> triangles' interior angles sum to 180 degrees exactly.
>
> 3) Hyperbolic (Riemannian) geometry: An infintie number of lines
> lines are parallel to a given line; all triangles' interior angles sum to
> <180 degrees.
So a shape which is not a triangle as defined by Euclidean geometry, does
not follow the definition of a Euclidean triangle. I believe this is what
your first post said, in a nut shell, and I still don't see why it is such
an amazing revelation. As you summarize above, the shape you described is
not a triangle in the Euclidean sense and therefore the sum of the
interior angles should not be 180 degrees.
Eric Lucas
Jeffrey Bodwin <bodw...@umich.edu> wrote in article
<Pine.SGI.3.95.970108...@Mn.Chem.LSA.UMich.Edu>...
> On 7 Jan 1997, Alan "Uncle Al" Schwartz wrote:
> {snip}
> > (BTW, everybody has been lying to you. Take a globe of the Earth.
Make
> > a segment of the equator one side of a triangle. Make the North Pole
one
> > vertex. Make any two lines of longitude the other two sides. Add up
the
> > sum of the interior angles of the triangles. It's more than 180
degrees
> > no matter how you slice it. Euclid is incomplete.)
> >
> What? Maybe I don't get the joke you're trying to make, but your line of
> reasoning is just wrong here. A triangle is a closed, three-sided planar
> figure in which the sum of the interior angles is 180 degrees. The figure
> you describe above is no more a triangle than my ass is a daisy. All
three
> sides of such a figure are curved and therefore the interior angles
> wouldn't be expected to add up to 180 degrees.
>
> Stick to the chemistry, Al.
No, you should stick to chemistry, Jeff. Al's right. To beings that exist
only on the surface of that sphere (i.e., 2-dimensional figures), that is
indeed a triangle. The lines are all straight from the perspective of the
surface of the sphere, and thus it is a triangle, and the angles don't add
up to 180 deg. The only reason you say that those lines are curved is that
you look at that 2-dimensional surface from a 3-dimensional perspective.
Euclidian geometry is the geometry of common experience, and it is thus
difficult to perceive of geometries in which the Euclidian postulates don't
hold. Like one in which parallel lines do intersect (remember, it's only a
postulate that they don't), and thus triangles don't necessarily have
interior angles that sum to 180 deg (which is a theorem that depends on the
parallel postulate). However, such geometries do exist, and have
usefulness in various aspects of science. Euclidian geometry explains
everyday observations well, but things like relativity and space-time
curvature make it such that other geometries (Riemann and Lobachevsky, if
my math education isn't too faint in my mind) are better representations of
reality. Just like Newtonian mechanics explains everyday experience
adequately, and quantum mechanics is difficult to understand from a
perspective of everyday experience, but quantum mechanics is needed to
explain more sophisticated observations of the world.
Eric Lucas
Dave Newbold
In article <01bbfd82$cd1c9980$fcac11cf@lucasea-home>, "Eric Lucas" <lu...@superlink.net> writes:
|>Jeffrey Bodwin <bodw...@umich.edu> wrote in article
|><Pine.SGI.3.95.970108...@Mn.Chem.LSA.UMich.Edu>...
|>> What? Maybe I don't get the joke you're trying to make, but your line of
|>> reasoning is just wrong here. A triangle is a closed, three-sided planar
|>> figure in which the sum of the interior angles is 180 degrees. The figure
|>> you describe above is no more a triangle than my ass is a daisy. All
|>three
|>> sides of such a figure are curved and therefore the interior angles
|>> wouldn't be expected to add up to 180 degrees.
|>>
|>> Stick to the chemistry, Al.
|>
|>No, you should stick to chemistry, Jeff. Al's right. To beings that exist
|>only on the surface of that sphere (i.e., 2-dimensional figures), that is
|>indeed a triangle. The lines are all straight from the perspective of the
|>surface of the sphere, and thus it is a triangle, and the angles don't add
|>up to 180 deg. The only reason you say that those lines are curved is that
|>you look at that 2-dimensional surface from a 3-dimensional perspective.
Not really. It is possible for beings in 2-space to measure the curvature
of their world as it would appear in 3-space. (Likewise, it is possible to measure
the curvature of 4-space, regardless of the absence of an embedding 5-space [?]).
Therefore, the lines aren't straight in the Euclidean sense, that geometry only
applying to flat space. There is no "perspective of the surface of a sphere"
globally (excuse the pun), only local curvature.
|>Euclidian geometry is the geometry of common experience, and it is thus
|>difficult to perceive of geometries in which the Euclidian postulates don't
|>hold. Like one in which parallel lines do intersect (remember, it's only a
|>postulate that they don't), and thus triangles don't necessarily have
|>interior angles that sum to 180 deg (which is a theorem that depends on the
|>parallel postulate).
I would think that the behaviour of parallel lines is axiomatic. That is, it
arises straight away from the definition of the metric? => Not a postulate
(I am ready to be corrected on this). However, if you define a triangle as
a "closed figure with three vertices and geodesic sides" then the above statement is
certainly correct. If you define it like that. Isn't this all a bit tortological? 8-).
Dave
--
"Humour is the very essence of a democratic society" -- Anon
Don Wilkins
On 7 Jan 1997 23:15:12 GMT, "Eric Lucas" <lu...@superlink.net> wrote:
>
>
>Your Actual Name <your...@ppg.com> wrote in article
><5auadb$h...@news.ppg.com>...
>> biom...@wimsey.com (Brad Brush) writes: > We have come upon a chemical
>that we cannot explain at our school. It is
>> > called Iron ferrosferric (natural magnetite), formula Fe3O4, one of the
>iron
>> > oxides.
>> >
>> > The combining capacity of oxgyen is almost always -2 (except for
>peroxides).
>> > Iron has a capacity of 2 or 3. This does not come out to be a ratio
>with intact
>> > integers. How can I explain this?
>> > Thanks.
>> >
>> You are almost always correct in saying that oxygen can be counted as a
>> -2. It works just fine in this case. As for iron, this is a mixed
>> system. Two of the iron atoms can be considered as having a formal +3
>> (ferric, Fe3+) charge and the remaining iron atom has a formal +2
>> (ferrous, Fe2+) charge. (sum of +8, charge is conserved and the crystal
>> does not explode) Remember, this assignment of charge is just a model.
>> The actual charges assigned by a more sophisticated quantum mechanical
>> (ab initio) model would show far more delocaliztion. However, the mixed
>> states explanation holds well for high school chemistry.
>
>In fact, I think I remember seeing the crystal structure for this material
>once, and it had two different Fe sites in the lattice in a 2:1 ratio, and
>the geometries about these sites were consistent with the formal charge
>assignments of 2 Fe(III) and 1 Fe(II). I guess I also thought that, unless
>there are Fe-Fe bonds (which I don't think there were), that spin
>delocalization through Fe-O-Fe interactions doesn't happen, and therefore
>the unpaired spins are localized on Fe's that are formally Fe(III).
>
>Can anyone verify?
>
Fe304 has the spinel structure (M+2)(M+3)204. Look for information on
ferrites. There have been hundreds made with various magnetic
properties. The alpha-Fe203 has the corundum type lattice like Al203
or Cr203. The gamma form is a ferrite and magnetic.
Malcolm Walters
Alan "Uncle Al" Schwartz wrote:
>
> >On 7 Jan 1997, Alan "Uncle Al" Schwartz wrote:
> >{snip}
> >>
> >What? Maybe I don't get the joke you're trying to make, but your line of
> >reasoning is just wrong here. A triangle is a closed, three-sided planar
> >figure in which the sum of the interior angles is 180 degrees. The figure
> >you describe above is no more a triangle than my ass is a daisy. All three
> >sides of such a figure are curved and therefore the interior angles
> >wouldn't be expected to add up to 180 degrees.
> >
> >Stick to the chemistry, Al.
>
> by lines tracing the shortest distances between the three pairs of them.
>
> given line; all triangles' interior angles sum to >180 degrees. In the
> special case of the surface of a sphere: geodesics, "straight lines," are
> segments of great circles (the shortest distance between two points).
>
to lie on the surface. The shortest distance between three points on the
earth surface cuts through the ground. This follows normal (euclidian)
geometry. I know this isn't much use to people normally since planes
can't fly through the ground.
> 2) Plane (Euclidian) geometry: One line parallel to a given line; all
> triangles' interior angles sum to 180 degrees exactly.
>
> 3) Hyperbolic (Riemannian) geometry: An infintie number of lines
> lines are parallel to a given line; all triangles' interior angles sum to
> <180 degrees.
>
Don Wilkins
On Thu, 09 Jan 1997 03:00:20 GMT, k...@insync.net (Casey Donovan)
wrote:
>dwil...@means.net (Don Wilkins) wrote:
>
>>On Wed, 08 Jan 1997 01:50:19 GMT, k...@insync.net (Casey Donovan)
>>wrote:
>
>>>BTW, it is magnetic, whereas Fe2O3 and (I think) FeO are not.
>>>This is a standard, though of course not definitive, test for its
>>>presence in a deposit.
>>>
>
>>Now let see if I have this straight. The gamma-Fe2O3 used in recording
>>tape is the figment of the manufacturers imagination.
>>
>>Gamma-Fe2O3 is made by the oxidation of Fe3O4, retains the spinel
>>structure and is in fact magnetic. It changes to the non-magnetic
>>alpha-Fe2O3 at 600.
>>
>>Nicht wahr
>
>Ich danke Ihnen. Mein Fehler. I was thinking only of
>water-formed oxides, and forgot about gamma-Fe2O3. I'm sure it
>is not imaginary.
>
Ja aber ein kleiner Fehler. Es macht nichts aus.
>
Peter Mott
Brad Brush wrote:
>
> We have come upon a chemical that we cannot explain at our school. It is
> called Iron ferrosferric (natural magnetite), formula Fe3O4, one of the iron
> oxides.
>
> The combining capacity of oxgyen is almost always -2 (except for peroxides).
> Iron has a capacity of 2 or 3. This does not come out to be a ratio with intact
> integers. How can I explain this?
Magnetite, Fe3O4, forms an inverse-spinal crystal structure. In this
structure, the larger oxygen ions are arrange in a close-packed cubic
(i.e., face-centered cubic) array, and the smaller cations (i.e., iron)
are occupy the octahedral and tetrhedral interesticies of the anion
structure. The unit cell contains 32 oxygen sites, which gives 32
octahedrally- and 64 tetrehedrally-coordinated intersticies. In the
spinel structure, 16 of the octahedral and 8 of the tetrahedral sites
are occupied by anions. An octahedral site is where the cation is
coordinated
by eight anions -- think of iron surrounded by oxygen on both sides on
the x, y, and z-axis; a tetrahedral site is where the cation is
coordinated
by four anions -- think of the iron in the middle of a pyramid with a
triangular base, and the oxygens at the corners.
In magnetite, iron filling the 8 tetrahedral sites are trivalent, and
the
16 octahedral sites are equally divided between di- and trivalent ions.
Ref: Kingery, Bowen and Uhlmann, "Introduction to Ceramics", p 991-993.
Peter Mott