earlk on thu 10 nov 05
Execllent Bruce !! But let me throw a wrinkle at you.
Suppose in your clay (or glaze) you have Fe2O3 (an oxidized
metal) and some organic material (algae, bacteria, mold, skin
cells). For simplicity let's assume the organic material is
something like CH3-CH2-CH2...CH2-CH3.
Now when you heat this in an inert atmosphere the organic
material will break down into pieces like CH3+, CH2++,
CH+++, H+ amongst others. These pieces will want to balance
out their charge, and in fact further oxidize to the lowest energy
state of CO2 and H2O, so won't they steal oxygen from the Fe2O3
and reduce it to FeO?
Wouldn't you actually get reduction effects in an inert atmosphere?
earlk
bothell, wa, usa
Earl Brunner on thu 10 nov 05
If this were actually the case, wouldn't the atmosphere actually turn reducing, due to the organics you mentioned? The reason I'm asking is that one of the reasons most people don't reduce in an electric kiln is because of the affect of the reduction on the elements. The only advantage I could see from using an inert gas would be if you could get reduction affects without materially affecting the life or performance of the elements.
earlk wrote:Execllent Bruce !! But let me throw a wrinkle at you.
Suppose in your clay (or glaze) you have Fe2O3 (an oxidized
metal) and some organic material (algae, bacteria, mold, skin
cells). For simplicity let's assume the organic material is
something like CH3-CH2-CH2...CH2-CH3.
Now when you heat this in an inert atmosphere the organic
material will break down into pieces like CH3+, CH2++,
CH+++, H+ amongst others. These pieces will want to balance
out their charge, and in fact further oxidize to the lowest energy
state of CO2 and H2O, so won't they steal oxygen from the Fe2O3
and reduce it to FeO?
Wouldn't you actually get reduction effects in an inert atmosphere?
earlk
bothell, wa, usa
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Earl Brunner
e-mail: brunv53@yahoo.com
Bruce Girrell on thu 10 nov 05
Tig Dupre wrote:
>Why wouldn't the addition of argon cause a similar effect?
Because operating in an _inert_ atmosphere is not the same as operating in a
_reducing_ atmosphere.
Before talking about reduction, though, let me say a little about its
opposite: oxidation.
When a metal* is in its elemental state, that is when you can actually hold
a piece of copper, iron, nickel, or whatever in your hand, then it has what
is called a "valence" state of zero. The valence state describes how many
atomic bonds can be made with another atom. When these elements are placed
in close proximity to other active elements, such as oxygen and there is
sufficient energy about, they lose or share some of their electrons and form
a chemical bond with the other element. For example, sodium (Na) becomes
sodium oxide.
Sodium really only has one electron that it can give up, so it goes to a
valence state of +1 by giving up its electron. Its valence state has been
_increased_. In this state it is capable of forming a chemical bond. Oxygen
likes to take on extra electrons. It really, really, likes to take on two
electrons. So to make a chemical compound with oxygen we need two sodium
atoms. Each sodium atoms gives up one electron and the oxygen atom takes on
both. We end up with Na2O (the 2 should be a subscript there). Each sodium
atoms has gone to a valence state of +1 and the oxygen has gone to a state
of -2. Note that the total of the valence states is zero (+1 +1 -2 = 0). We
say that the metal has been oxidized.
One state that iron likes is a +3 valence. Since oxygen has a -2, the
combination that works is two iron atoms and three oxygen atoms to form
Fe2O3. Two iron atoms at +3 = +6 and three oxygen atoms at -2 = -6. This is
one form of iron oxide. Iron can also go to a valence state of +2. If that
is the case then the compound formed is FeO. If we had a molecule of Fe2O3
and, through some chemical magic that gives each iron atom back one of its
electrons, we changed the valence state of the iron from +3 to +2 then the
Fe2O3 would split up into FeO + FeO + O. Count 'em up. There are still two
iron atoms and three oxygen atoms but they have been rearranged. The valence
state of the iron has been _reduced_ from 3 to 2 by the removal of an oxygen
atom.
That is where the term "to reduce" or "reduction" comes from. We reduce the
valence state of an oxidized metal by removing some or all of the oxygen to
which it is attached.
If I had some copper oxide, CuO (copper here has a valence state of +2) and
I removed the oxygen and gave the two electrons back to the copper, then I
would _reduce_ the copper oxide to elemental copper with a valence state of
zero.
Note that in each case, the reduction is accomplished by the removal of
oxygen.
Carbon likes to go to a valence state of +4 and hot carbon really, really
likes oxygen. It likes oxygen so much that it will take it away from other
compounds that have already bound with it. Since each carbon atom is at +4
it needs two oxygens at -2 to combine with in order to produce CO2. You can
think of the hot carbon like a hot woman/man who shows up in a crowded bar
filled with somewhat bored metal oxide couples. The bored oxygen dumps
his/her date to hook up with the hot carbon - and the abandoned metal is
reduced to tears. OK, maybe not the best analogy, but I'm trying to liven
this up a little.
What it boils down to is that something - something that is very chemically
reactive - is required to entice the oxygen away from its metal partner. You
need hydrogen, carbon or something else that wants the oxygen more than the
metal oxide wants it. An inert atmosphere won't do it.
Inert atmospheres are great for preventing oxidation, but they won't give
you reduction.
Bruce "class dismissed" Girrell
*Yes, it can be something other than a metal, but for our purposes, let's
limit it to a metal. And oxidation can be accomplished by something other
than oxygen. But if you already knew that then you didn't need my little
simplified version.
Hank Murrow on thu 10 nov 05
Thank you Bruce! Lovely! Do another when it comes up!
Cheers, Hank
On Nov 10, 2005, at 1:34 PM, Bruce Girrell wrote:
> Tig Dupre wrote:
>
>> Why wouldn't the addition of argon cause a similar effect?
>
> Because operating in an _inert_ atmosphere is not the same as
> operating in a
> _reducing_ atmosphere.
>
> Before talking about reduction, though, let me say a little about its
> opposite: oxidation.
>
> When a metal* is in its elemental state, that is when you can actually
> hold
> a piece of copper, iron, nickel, or whatever in your hand, then it has
> what
> is called a "valence" state of zero. The valence state describes how
> many
> atomic bonds can be made with another atom. When these elements are
> placed
> in close proximity to other active elements, such as oxygen and there
> is
> sufficient energy about, they lose or share some of their electrons
> and form
> a chemical bond with the other element. For example, sodium (Na)
> becomes
> sodium oxide.
>
> Sodium really only has one electron that it can give up, so it goes to
> a
> valence state of +1 by giving up its electron. Its valence state has
> been
> _increased_. In this state it is capable of forming a chemical bond.
> Oxygen
> likes to take on extra electrons. It really, really, likes to take on
> two
> electrons. So to make a chemical compound with oxygen we need two
> sodium
> atoms. Each sodium atoms gives up one electron and the oxygen atom
> takes on
> both. We end up with Na2O (the 2 should be a subscript there). Each
> sodium
> atoms has gone to a valence state of +1 and the oxygen has gone to a
> state
> of -2. Note that the total of the valence states is zero (+1 +1 -2 =
> 0). We
> say that the metal has been oxidized.
>
> One state that iron likes is a +3 valence. Since oxygen has a -2, the
> combination that works is two iron atoms and three oxygen atoms to form
> Fe2O3. Two iron atoms at +3 = +6 and three oxygen atoms at -2 = -6.
> This is
> one form of iron oxide. Iron can also go to a valence state of +2. If
> that
> is the case then the compound formed is FeO. If we had a molecule of
> Fe2O3
> and, through some chemical magic that gives each iron atom back one of
> its
> electrons, we changed the valence state of the iron from +3 to +2 then
> the
> Fe2O3 would split up into FeO + FeO + O. Count 'em up. There are still
> two
> iron atoms and three oxygen atoms but they have been rearranged. The
> valence
> state of the iron has been _reduced_ from 3 to 2 by the removal of an
> oxygen
> atom.
>
> That is where the term "to reduce" or "reduction" comes from. We
> reduce the
> valence state of an oxidized metal by removing some or all of the
> oxygen to
> which it is attached.
>
> If I had some copper oxide, CuO (copper here has a valence state of
> +2) and
> I removed the oxygen and gave the two electrons back to the copper,
> then I
> would _reduce_ the copper oxide to elemental copper with a valence
> state of
> zero.
>
> Note that in each case, the reduction is accomplished by the removal of
> oxygen.
>
> Carbon likes to go to a valence state of +4 and hot carbon really,
> really
> likes oxygen. It likes oxygen so much that it will take it away from
> other
> compounds that have already bound with it. Since each carbon atom is
> at +4
> it needs two oxygens at -2 to combine with in order to produce CO2.
> You can
> think of the hot carbon like a hot woman/man who shows up in a crowded
> bar
> filled with somewhat bored metal oxide couples. The bored oxygen dumps
> his/her date to hook up with the hot carbon - and the abandoned metal
> is
> reduced to tears. OK, maybe not the best analogy, but I'm trying to
> liven
> this up a little.
>
> What it boils down to is that something - something that is very
> chemically
> reactive - is required to entice the oxygen away from its metal
> partner. You
> need hydrogen, carbon or something else that wants the oxygen more
> than the
> metal oxide wants it. An inert atmosphere won't do it.
>
> Inert atmospheres are great for preventing oxidation, but they won't
> give
> you reduction.
>
> Bruce "class dismissed" Girrell
>
>
> *Yes, it can be something other than a metal, but for our purposes,
> let's
> limit it to a metal. And oxidation can be accomplished by something
> other
> than oxygen. But if you already knew that then you didn't need my
> little
> simplified version.
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
>
www.murrow.biz/hank
Bruce Girrell on fri 11 nov 05
earlk wrote:
> Execllent Bruce !! But let me throw a wrinkle at you.
But that's no different from taking your CH3-CH2-CH3 or CH4 in abundant
supply and combining some it with atmospheric O2 thereby depleting the O2,
leaving excess CH3-CH2-CH3 or CH4 to break down and react with the oxides in
the glazes.
In other words, it is the same as turning up the fuel or reducing the air
intake to achieve reduction like we always do. Introducing an inert gas is
just a more expensive way of limiting the oxygen.
Bruce
Lester Haworth on fri 11 nov 05
Hank,
You Rock! Thanks for the breif lesson. This post is archive material!
Reminded me of my chemistry teacher in high school trying to drill all of
this stuff into my thick skull.
Maybe i'm just a little more interested cause it's related to ceramics...
Sometimes I enjoy being exposed
to an excellent teacher who can feed me enough information and bring me to
the point of sensory overload.
I think I learn so much more and retain it better than any other type of
instruction.
Thanks again Hank,
Les H.
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Hank Murrow
Sent: Thursday, November 10, 2005 4:10 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Non-Carbon Reduction (somewhat long chemistry lesson)
Thank you Bruce! Lovely! Do another when it comes up!
Cheers, Hank
On Nov 10, 2005, at 1:34 PM, Bruce Girrell wrote:
> Tig Dupre wrote:
>
>> Why wouldn't the addition of argon cause a similar effect?
>
> Because operating in an _inert_ atmosphere is not the same as
> operating in a
> _reducing_ atmosphere.
>
> Before talking about reduction, though, let me say a little about its
> opposite: oxidation.
>
> When a metal* is in its elemental state, that is when you can actually
> hold
> a piece of copper, iron, nickel, or whatever in your hand, then it has
> what
> is called a "valence" state of zero. The valence state describes how
> many
> atomic bonds can be made with another atom. When these elements are
> placed
> in close proximity to other active elements, such as oxygen and there
> is
> sufficient energy about, they lose or share some of their electrons
> and form
> a chemical bond with the other element. For example, sodium (Na)
> becomes
> sodium oxide.
>
> Sodium really only has one electron that it can give up, so it goes to
> a
> valence state of +1 by giving up its electron. Its valence state has
> been
> _increased_. In this state it is capable of forming a chemical bond.
> Oxygen
> likes to take on extra electrons. It really, really, likes to take on
> two
> electrons. So to make a chemical compound with oxygen we need two
> sodium
> atoms. Each sodium atoms gives up one electron and the oxygen atom
> takes on
> both. We end up with Na2O (the 2 should be a subscript there). Each
> sodium
> atoms has gone to a valence state of +1 and the oxygen has gone to a
> state
> of -2. Note that the total of the valence states is zero (+1 +1 -2 =
> 0). We
> say that the metal has been oxidized.
>
> One state that iron likes is a +3 valence. Since oxygen has a -2, the
> combination that works is two iron atoms and three oxygen atoms to form
> Fe2O3. Two iron atoms at +3 = +6 and three oxygen atoms at -2 = -6.
> This is
> one form of iron oxide. Iron can also go to a valence state of +2. If
> that
> is the case then the compound formed is FeO. If we had a molecule of
> Fe2O3
> and, through some chemical magic that gives each iron atom back one of
> its
> electrons, we changed the valence state of the iron from +3 to +2 then
> the
> Fe2O3 would split up into FeO + FeO + O. Count 'em up. There are still
> two
> iron atoms and three oxygen atoms but they have been rearranged. The
> valence
> state of the iron has been _reduced_ from 3 to 2 by the removal of an
> oxygen
> atom.
>
> That is where the term "to reduce" or "reduction" comes from. We
> reduce the
> valence state of an oxidized metal by removing some or all of the
> oxygen to
> which it is attached.
>
> If I had some copper oxide, CuO (copper here has a valence state of
> +2) and
> I removed the oxygen and gave the two electrons back to the copper,
> then I
> would _reduce_ the copper oxide to elemental copper with a valence
> state of
> zero.
>
> Note that in each case, the reduction is accomplished by the removal of
> oxygen.
>
> Carbon likes to go to a valence state of +4 and hot carbon really,
> really
> likes oxygen. It likes oxygen so much that it will take it away from
> other
> compounds that have already bound with it. Since each carbon atom is
> at +4
> it needs two oxygens at -2 to combine with in order to produce CO2.
> You can
> think of the hot carbon like a hot woman/man who shows up in a crowded
> bar
> filled with somewhat bored metal oxide couples. The bored oxygen dumps
> his/her date to hook up with the hot carbon - and the abandoned metal
> is
> reduced to tears. OK, maybe not the best analogy, but I'm trying to
> liven
> this up a little.
>
> What it boils down to is that something - something that is very
> chemically
> reactive - is required to entice the oxygen away from its metal
> partner. You
> need hydrogen, carbon or something else that wants the oxygen more
> than the
> metal oxide wants it. An inert atmosphere won't do it.
>
> Inert atmospheres are great for preventing oxidation, but they won't
> give
> you reduction.
>
> Bruce "class dismissed" Girrell
>
>
> *Yes, it can be something other than a metal, but for our purposes,
> let's
> limit it to a metal. And oxidation can be accomplished by something
> other
> than oxygen. But if you already knew that then you didn't need my
> little
> simplified version.
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
>
www.murrow.biz/hank
____________________________________________________________________________
__
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Ivor and Olive Lewis on tue 15 nov 05
Dear Earl,
You comment ""For simplicity let's assume the organic material is =
something like CH3-CH2-CH2...CH2-CH3.......when you heat this in an =
inert atmosphere the organic material will break down into pieces like =
CH3+, CH2++, CH+++, H+ amongst others......and ....further oxidize to =
the lowest energy state of CO2 and H2O, so won't they steal oxygen from =
the Fe2O3 and reduce it to FeO?.....Wouldn't you actually get reduction =
effects in an inert atmosphere? ....""
An interesting and as you say, simple and plausible thought. But if the =
partial pressure of oxygen is low enough that will happen anyway without =
the need for organic hydrocarbons. As the partial pressure of oxygen =
diminishes Fe2O3 may go through several changes, from Haematite to =
Magnetite then to W=FCstite and finally to Iron. All these reactions are =
Temperature, Energy, and Oxygen dependent.
Best regards,
Ivor.
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