semiconductive
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methanol/ionic liquid electroplaing of metals
I'm trying some experiments in methanol, to see how it compares to water electroplating.
Iron, for example, rapidly turns a water bath brown and rust forms during electo-deposition of metal. Rust sludge falls to the bottom of a water
bath. Only certain acids seem to be able to plate iron from water, and the results aren't very useful in most manufacturing settings.
So, I decided to try iron deposition from a methanol bath to see if I can control the rust issue and get more crystalline iron to plate out. I also
wanted to see if more electropositive metals, such as strontinum and calcium, could be electroplated from a bath containing methanol or methanol
salts.
I made potassium acetate from potassium carbonate and white vineagar; and then re-crystalizzed it twice to get rid of most impurities. This, I mixed
with methanol and began electrolysis between two steel electrodes.
An orange colored solution forms at the anode, and it diffuses into solution well.
If any solid forms, just a gentle shaking causes it to dissolve.
A dark colored deposit forms on the cathode. I expect this is iron monoxide, and I think there is probably a small amount of moisture in the
potassium acetate. If that's the case, the deposit could possibly turn grey or silvery in a day or two after the traces of moisture are destroyed.
What I am curious about, though, is how likely am I to get either acetate or methoxide embedded in the iron as it plates? Is there a theoretical way
to estimate the percentage I should get?
The cathode voltage is the most negative (reducing) of all reaction sources, and any potassium that plates out will want to go back into solution as
potassium acetate or potassium methoxide. So, I don't expect significant potassium to end up in the deposit because there is excess methanol
present as a solvent. K is too reactive to build up when liquid methanol is present.
That brings me to a second experiment with more electropositive metals, which rapidly react with methanol. Alkaline alkoxides are generally solids,
and can interfere with electrodeposition of more metal. Calcium acetate, when mixed with methanol, will also form a gel; and I don't know if that
would be conductive or not.
So, I want to avoid the gel.
I want another solvent that is not likely to react with calcium or strontium, but would tend to dissolve acetates. This will dillute the methanol
and reduce the rate it attacks an electropositive metal and hopefully prevent gel formation.
For my first attempt, I tried a methanol-acetate ester. I'm just thinking acetate and acetate ... are likely to dissolve each other since they are
alike'. I assume the ester will be relatively inert or at least slow reacting around calcium metal, but I'm not sure. Please advise.
Next, I made calcium acetate (a solid) and mixed it with the ester.
No obvious dissolution happened.
I added a few drops of methanol to the solution and applied voltage to a carbon anode and iron electrode. No current flowed at all. So, I added a
very small amount of ethylene carbonate.
Then the reaction started. It requires more than 3volts for significant current to flow. Ethylene carbonate is advertized as having a 4v working
window before it will participate in side reactions. So, I think it's possible for calcium metal to be reduced at the electrode, and be re-dissolved
by the methanol present.
Is my choice of solvent (ethane-acetate ester) likely to react with calcium ions or metal or not?
[Edited on 3-5-2021 by semiconductive]
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Boffis
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I don't think methanol is going to work for either group of metals, as you suggest . I think you will need an aprotic polar liquid such as an organic
carbonates, dioxane, ethylene-diethers such as glyme etc. I think you would reduce DMSO so that no good.
The tradition method of preparing alkaline earth metals was to use a mercury cathod and then distill off the mercury but that probably rather risky.
As for iron it should be possible since there is a commercial process used to electrowin zinc for hydrometallurgical solutions. This process is used
commercially in at least one mine I know of. I am not sure of the exact conditions but I am sure a google search will yield a link.
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DraconicAcid
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Quote: Originally posted by semiconductive  | | I'm just thinking acetate and acetate ... are likely to dissolve each other since they are alike'. I assume the ester will be relatively inert or at
least slow reacting around calcium metal, but I'm not sure. Please advise. |
That would be a poor assumption. An ionic acetate is nothing like an ester of acetic acid, and one will not be soluble in the other. Esters have
much lower polarity than alcohols, and are poor solvents for ionic compounds.
Ethylene carbonate is much more polar, and is likely to be a better solvent for what you are trying.
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rockyit98
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try Ethylene carbonate or propylene carbonate with iron perchlorates. Ethylene carbonate can be prepaid by urea and antifreeze with good vacuum pump
and ZnO as catalyst. try youtube.
"A mind is a terrible thing to lose"-Meisner
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semiconductive
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| Quote: |
That would be a poor assumption. An ionic acetate is nothing like an ester of acetic acid, and one will not be soluble in the other. Esters have
much lower polarity than alcohols, and are poor solvents for ionic compounds.
Ethylene carbonate is much more polar, and is likely to be a better solvent for what you are trying. |
I agree, from experiment it's not good solvent for the calcium acetate even though the metyl group of acetate and the methyl group of the ester are
the same for half the molecule. so, it's not like soap where half a molcule helps it dissolve in non-ionic, and half helps the ionic.
But, I'm more interested in the reactivity and some weirdness. Would the ester react wth calcium metal or hydroxide, or potassium metal or hydroxide?
This is why I ask: ethylene carbonate goes into ethanol-acetate ester after running electricity through the bi-layer for several days with even a tiny
amount of methanol in the solution (to make it conductive). Methanol appears to make ethylene carbonate soluble in ethanol-acetate ester. The
solubility increases rapidly as metal ions are dissolved; and that seems opposite of what you suggest. For metal in solutions should be ionic, and
decrease the solubility in the acetate-ester. Correct?
Here's what I did:
I added a chunk (2CC's and around 30%) of solid ethylene carbonate to the ester; and two drops of methoanol, along with potassium cabonate. The
cabonate stayed solid on the bottom.
I ran electricity through it the bi-layer with an iron cathode inside the ehylene-arbonate, and a carbon anode in the ester above. I wanted to make a
small amount of the potassium go into solution and wasn't trying to dissolve iron yet.
After a few days, I had a liquid and no more solid ethylene-carbonate at the bottom.
This disappointed me, because I was hoping the two would stay separate and help me isolate different molecules which might prefer one media to the
other. But, I guess I'll need a semipermiable membrane to do anythng like that.
I tried to evaporate the ester off, but the last 2cc's mostly stayed liquid even after cooling. I got less than 1/4cc of solid which was darkened by
the iron of the cathode. (The anode was carbon fiber, and perfectly clean.)
There was very little gas formed at the carbon anode, and almost all gas came from the cathode.
So, I'm wondering if the ester reacted with the etyhlene-carbonate, or the metal ions, ??
Why would the carbonate stay liquid after I tried to evaporate the ester off, especially when alkalai methoxides are gnerally solids?
Is this a Eutectic issue, or a chemical reaction issue.
How might I design an experiment to tell?
The test tube was sealed, so no moisture was entering during the multiple days.
It had gas pressure when I opened it, so there should be hydrogen and perhaps carbon dioxide in the tube preventing moisture from working it's way in.
The potassium carbonate is suppoed to be dry, reagent grade. So is the Ethylene cabonate. I was getting a 2.7 V back voltage after disconnecting
power , which generally means there couldn't be much water in the electrolyte or the 'battery' voltage would decay in seconds rather than in hours.
[Edited on 5-5-2021 by semiconductive]
[Edited on 5-5-2021 by semiconductive]
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semiconductive
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| Quote: Originally posted by rockyit98 | | try Ethylene carbonate or propylene carbonate with iron perchlorates. Ethylene carbonate can be prepaid by urea and antifreeze with good vacuum pump
and ZnO as catalyst. try youtube. |
Why perchlorates? Wouldn't that be explosive and rust causing?
I've tried electrolysis on KCl, before I bought reagant grade potassium carbonate. I thought I would drive off the chlorine as gas in KCL, (and
produce cheap potassium hydoxide.) Then I could that would react with my methanol to make a methoxide.
But, I got a very strong oxidizer ... as in INSTANT rust. I'm thinking it might have been potassium perchlorate, but I'm usually wrong. So, I'll
just let someone smarter answer.
But -- I'm wondering: wouldn't an iron perchlorate be prone to making rust?
I've been trying methanol over water, because the methyl group has a much stronger bond to the oxygen than hydrogen does. I'm hoping the methyls will
prevent the iron from absorbing the oxygen.
What's the supposed advantage of using iron perchlorate?
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semiconductive
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Small update .... The Iron in methanol with potassium acetate plates organ-metallic. It has a significant amount of grey iron in it ... but it is
spongey and mostly dark. Though, it's an actual deposit and not a sludge that falls off the electrode. The deposit is metallic enough to make a very
thick deposit overnight of several millimeters..
I added the ester to the electrolyte to see how soluble the iron ions were in ester. About 40% of my mixture (approximately the amount of methanol
present) misced with the ethanol-acetate ester making a dark orange liquid. After that, the liquids separated into two layers and the orange
condensed into a smaller space on the bottom of the test-tube. So, I assume the iron acetate is nearly insoluble in ethanol-acetate ester. I'm
merely extracting methanol out of the electrolyte with the ester.
The deposit is promising. Solid but spongey deposits in water based electrolytes usually means too high of an electroplating current.
So, I'll fiddle with it. Maybe reduced current will produce a better deposit in a non-aqueous electrolyte as well.
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DraconicAcid
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If you mean ethyl acetate, say ethyl acetate, not "ethanol-acetate ester". The iron may plate out of your methanol solution, but it's not
organometallic.
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Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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semiconductive
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I lookued up organometallic. Are you objecting because the oxygen an oxygen likely present? eg: it's not organometallic even though an organic acid
or methly group is still attached to the iron?
The iron is soft, and that's not because its spongey ... but because not all the acid/alcohol bonded to the iron leaves the surface as it plates. The
result is iron that still has acid attached to it, and possibly methanol.
Iron methoxide is called "organo-metallic" by american elements and others that sell it. I think that's a likely contaminant in the plating.
I assume you don't know if ethyl-acetate will react with sodium or potassium since you haven't answered, now, twice?
If so: I'm going to assume it doesn't react, because I can apply 12V to pure ethyacetate ... and no detectable current flows. Even with distilled
water, a little current will flow. So, I think the ester would be pretty stable in the presence of alkali metal. If it does react, I'm going to
assume (for now) that it probably is a slow reaction.
I added Ethyl-carbonate and ester, and will run it until the methanol (just a few drops was all I had in this vial) is chemcially exhausted. Perhaps
the plating color will change.
I think Ethyl carbonate dissolves slowly in ethyl acetate; at least when in the presence of metal ions. I'm going to hypothisize that Ethyl
carbonate is unlikely to release all the ethy acetate in a drying process, and that's why I end up with liquid when I try to drive off the ester with
heat.
Today's plating is much harder and denser (at lower currents) than before; but it's also very rough and dark grey to black. It's not plating
smoothly, either. That could be because of the large amount of potassium that is present.
I don't think there's much organics adhering to this deposit. It turns brown on exposure to air, though. So, maybe a small amount of the methanol is
breaking down and releasing oxygen?
The solution varies between yellow and dark red depending on dillution; The red liquid sinks to the bottom of the vial. There's no brown color ... so
I'm fairly confident that I have iron tri-acetate as the major constituent. I'm not sure what the yellowish color is, but maybe that's just very
dilute iron tri-acetate. Iron tri-acetate doesn't dissolve well in the ester.
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DraconicAcid
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| Quote: | I lookued up organometallic. Are you objecting because the oxygen an oxygen likely present? eg: it's not organometallic even though an organic acid
or methly group is still attached to the iron?
The iron is soft, and that's not because its spongey ... but because not all the acid/alcohol bonded to the iron leaves the surface as it plates. The
result is iron that still has acid attached to it, and possibly methanol. |
You've got iron. Maybe it's rusty, maybe it's dirty, but it's iron, not an organometallic iron compound.
| Quote: | | Iron methoxide is called "organo-metallic" by american elements and others that sell it. I think that's a likely contaminant in the plating.
|
It does not contain an iron-carbon bond, so it is not organometallic, despite what the salespeople say.
| Quote: | I assume you don't know if ethyl-acetate will react with sodium or potassium since you haven't answered, now, twice?
If so: I'm going to assume it doesn't react, because I can apply 12V to pure ethyacetate ... and no detectable current flows. |
That doesn't say anything about whether ethyl acetate will react with either metal- it just means it's a nonconductor. There's no ions in the
solution,so why should it conduct?
If there is even a trace of moisture present, then the sodium or potssium hydroxide formed will hydrolyse the ethyl acetate pretty quickly.
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Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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semiconductive
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| Quote: |
does not contain an iron-carbon bond, so it is not organometallic, despite what the salespeople say.
|
Ok, so that's what I was wanting to know. Thanks.
| Quote: |
That doesn't say anything about whether ethyl acetate will react with either metal- it just means it's a nonconductor. There's no ions in the
solution,so why should it conduct?
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When atoms exeprience large fields, that often will cause chemical reactions. There's a difference in the density of the field from a dilopar
moelcule, and a dipolar pair of electrodes. But, they are the same thing in their physics; ... they are both an energy bearing field with so many
electron-volts of energy capability. SO, if I apply an electric field to a non-polar molecule, I can often induce a dipole moment in the molecule and
even cause reduction or oxidations to happen at electrodes (given a sufficiently large voltage applied). A liquid without ions can sometimes be made
conductive by an electric field, itself.
There are certainly quantum mechanical issues, etc. that I'm overlooking. And I'd be interested to know how water increases the reaction that breaks
down the ester. But, in general ... a liquid which can withstand a high voltage applied to it; is going to have more stable and chemically resistant
bonds than another liquid which doesn't.
So, a voltage/conductivity test is one way to find out how stable a liquid's bonds are.
It's not a definitive test, but it's a test I can do.
I'm not sure what's going on with carboxyic esters.
The chemicals I can get easily to experiment with are generally going to be carboxylic acids and alcohols, ketones, and halides. There are more
exotic chemicals, such as thiols that don't have oxygen ... but those tend to stink, and easily obtainable ones will still have oxygen. DMSO is an
example, and if I remove the O, to get DMS -- it stinks. In electroplating, saccharine is often used; but it has oxygen.
Since oxygen is so common in organic acids, I'm trying to understand what makes the oxygen more or less reactive and likely to produce rust or a
chemical bond to iron that isn't easy to break or 'dissolve' away.
I've tried things like Acetone, where the oxygen is in a double bond; and when I raise the voltage acetone conducts very much like an alcohol. THe
voltage knee almost make me think it is an alcohol. In the presence of metal, acetone will rapidly will become a good conductor. I generally end up
with metallic sludge. So, I'm pretty sure there's another radical that acetone's oxgen easily converts into -- a radical that's very similar to an
alcohol. The hydrocarbon parts of the molecule don't normally convert into a good conductor (eg: in alkanes for example.) So -- it has to be
something about the oxygen which is causing my problems.
Carboxylic acids also have an oxygen in a double bond, but for some reason the carboxylic esters that I've tried do not rapidly become good conductors
when voltages are applied at metal electrodes.
Apparantly, the second oxygen in a carboxylate, prevents whatever ?tautomerization? or ?isomerization? can easily happen in ketones. I think Ehtyl
acetate is very similar to acetone, in other ways. The ester will (for example) dissolve uncured RTV silicone quite well. It;s a better solvent
than aliaphatic oils for RTV silicone. But the ester does less chemical damage to the RTV silicone. Hardened RTV after exposure to ketones are much
weaker than after exposure to ethyl acetate.
I haven't come across information which tells me how likely a carboxylic acid's oxygens are to break off and become rust on an iron atom (or to bond
an organic to the iron through the oxygen). But, from the experiments I've done ... carboxylic esters are less reactive than ketones.
Right now, I'm trying acetates. But, I've ordered calcium formate and formate esters to experiment with.
Formic acid has a different pKa, so might have differnt reactivity. I thought it was more acidic, but looking again I think I made a mistake. but,
if it's less acidic ... then it might form more stable esters. I'll just have to see what happens.
I also see MSM, (DMSO2), is reported to be less reactive than DMSO. I dont' know why that is, but it makes me curious.
[Edited on 7-5-2021 by semiconductive]
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clearly_not_atara
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pKa H2O: 15.7
pKa MeOH: 15.5
Methanol gets you practically nothing as far as stability for electrodeposition. The chemical potential of protons is basically the same.
But the good news is that anhydrous FeCl2 can be obtained from methanol solutions and has good solubility in organic solvents, which is a start.
[Edited on 04-20-1969 by clearly_not_atara]
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semiconductive
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@clearly_not_atara
Yes ...protic hydrogen releases from methanol just about as easily as from water.
And that shows up in my solutions as hydrogen bubbing out at the cathode.
But, isn't the R-O bond stronger than the H-O bond, so that methanol is less likely to release oxygen to a metal? eg: prevent the oxygen from making
a double bond to the metal.
In higher alcohols, I thoght they tend to act more like a base; so doesn't that mean that isopropyl alcohol is more likely to release the "OH' radical
than methanol is ?
I mean, what's the liklihood of methanol releasing oxygen at an electrode and becoming ethene with 12 volts or less applied ?
Is that more or less likely than isopropyl alcohol releasing an oxygen/or hydroxide ?
I have FeCl3.
If I mix that with methanol, will it reduce to FeCl2? Or do I need to use something like ascorbic acid?
[Edited on 12-5-2021 by semiconductive]
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DraconicAcid
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Isopropanol isn't going to give up a hydroxyl radical or hydroxide in a neutral solution.
If you reduce an alcohol, it will be 2 R2CHOH + 2 e- --> 2 R2CHO(-) + H2
If you oxidize it, it will be R2CHOH --> R2C=O + 2 H(+) + 2 e-.
Whether a metal alkoxide will undergo elimination to give a metal oxide or not is not within my experience.
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semiconductive
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Hmmm .... Let me review my ideas and tell me if I'm mistaken, it's been a few years since I checked:
Acid:
The Arrhenius idea is the donation of a hydrogen.
Bronstead Lowery idea is a neutral chemical able to absorb a negative ion, or to donate a positive one ion.
eg: AlOH3 + OH- = Al(OH)4 - ( Aluminum acting as an acid by absorbing a negative ion )
A base:
Something that will absorb a positively charged ion.
eg: AlOH3 + 3H+ = 3H2O + Al_3+
Aluminum hydroxide is amphoteric and will do either, and water is also ampoteric.
With alcohols, I understand methanol's acidity to be the Arrhenius idea.
But various texts say that only methanol is an acidic alcohol, and all others are more 'basic', what are they referring to?
From the pKa of methanol, methanol is more likely to disassociate than water is ... so I get that.
But, when I check the pKa of isopropyl,it's 16.5.
So, isopropyl is a weaker acid than water is ... but it still acts as an acid,correct?
I don't recall ever reading about a neutral Isopropyl molecule acting as a base (in water) and become positively charged by absorbing a hydrogen ion.
So, alcohols normally act only as conjugate bases ?
[Edited on 12-5-2021 by semiconductive]
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DraconicAcid
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| Quote: Originally posted by semiconductive | Hmmm .... Let me review my ideas and tell me if I'm mistaken, it's been a few years since I checked:
Acid:
The Arrhenius idea is the donation of a hydrogen.
Bronstead Lowery idea is a neutral chemical able to absorb a negative ion, or to donate a positive one ion.
eg: AlOH3 + OH- = Al(OH)4 - ( Aluminum acting as an acid by absorbing a negative ion )
A base:
Something that will absorb a positively charged ion.
eg: AlOH3 + 3H+ = 3H2O + Al_3+
Aluminum hydroxide is amphoteric and will do either, and water is also ampoteric.
With alcohols, I understand methanol's acidity to be the Arrhenius idea.
But various texts say that only methanol is an acidic alcohol, and all others are more 'basic', what are they referring to?
From the pKa of methanol, methanol is more likely to disassociate than water is ... so I get that.
But, when I check the pKa of isopropyl,it's 16.5.
So, isopropyl is a weaker acid than water is ... but it still acts as an acid,correct?
I don't recall ever reading about a neutral Isopropyl molecule acting as a base (in water) and become positively charged by absorbing a hydrogen ion.
So, alcohols normally act only as conjugate bases ?
[Edited on 12-5-2021 by semiconductive] |
Arrhenius declared that acids dissociate in water to give H+ ions, and that bases dissociate in water to give hydroxide ions. Nobody uses Arrhenius
outside of grade 10 chemistry courses.
Bronsted-Lowry defined acids as species that will give up H+ in a chemical reaction, and bases as species that will accept H+ in a chemical reaction.
So ammonia isn't a base according to Arrhenius (it doesn't contain hydroxide), and Al(OH)3 isn't an acid according to B-L (it doesn't give up H+).
According to the Lewis definition, an acid will accept a pair of electrons, and a base will supply them.
In aqueous solution, alcohols are feeble acids- they have no acidic character in aqueous solution, because they are less acidic than water. They are
also less basic than water, so they are essentially inert in aqueous solution (as far as acid-base chemistry goes). You can make their conjugate
bases and acids in other solvents, but they would immediately react with water if given the chance, and will not exist in aqueous solution.
In non-aqueous solvents, methanol is more acidic than other alcohols, and is more likely to give up a proton to form methoxide ion. Just not if water
(which is more acidic) is around.
Alcohols can be protonated to give ROH2(+) cations (similar to the hydronium ion H3O+). The more basic they are, the more easily protonated they are.
Depending on the alcohol, some of these cations can decompose by eliminating water (giving a carbocation, often followed by deprotonation to give an
alkene, or reaction with another alcohol to give an ether).
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semiconductive
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Oh, I see. I was mixing up Lewis idea with Bronstead-Lowry.
Bronstead is strictly hydrogen transfer .... and lewis is the electrophile, nucleophile generalization that works even in non-aqueous non hydrogen
situations.
When you say 'less basic', you mean the molecule is less likely to accept hydrogen ions?
OK.
If an alcohol is protinated, does the hydrogen weakly attach to the oxygen like hydrogen does in hydronioum ions?
I'm not sure what you mean about methanol vs. water.
The pKa values for methanol and water, listed earlier by another poster, shows methanol to be slightly lower exponent; so doesn't that means it's more
likely to release hydrogen than water would ?
Isn't a lower pKa number equivalent to a smaller negative exponent?
(Eg: a larger value since 10^-3 is bigger than 10^-4).
Or is that pKa measured in a way that I'm not understanding?
When I look at acetic acid, vs. Formic acid, I mixed up the numbers earlier.
I checked again, and pKa formic is listed as 3.745, and pKa acetic is 4.756 according to wikipedia. (numbers that are easy to get dsylexic about.
 ) But, I decided to check my idea about pKa's.
I think these numbers should be for water based measurements at some specific concentration. I vaguely recall that concentration can affect
ionization constants. I think at low concentrations, ionization is more likely to happen.
However, I simply think of the carboxylic acids as oxygenated versions of the corresponding alcohols; then I expect that formic acid and acetic
acid, correspond to methanol and ethanol. The pKa's should also follow the same trend as the alcohols. The shorter chain will have a lower pKa
number, and be a stronger proton donor.
When I do some research,
I see people claim that formic acid is stronger than acetic, so I think I have the pKa relationship correct. The pKa's system seems to suggest that
smaller numbers mean stronger acids / proton donors.
Note:
I tried using calcium formate in the same experiment that I earlier used potassium acetate with. I was surprised. I got almost no conductivity
(2.6 mega ohms resistance) with ethylene carbonate and the ester as solvents, I got about the same with a methanol and ester mix. Apparently formic
acid salts (at least calcium salts) are much less soluble in the ester than acetic acid salts.
An odd thing happened, though, when I add both ethylene carbonate AND methanol and let it sit under potential over-night. The resistance dropped and
iron begins going into solution although my LED current indicator was very dim.
When I pulled the anode out of the salt at the bottom of the tube, the current level rose enough to make the LED glow brightly.
I get a yellow iron deposit on the cathode.
The reaction nearly stops when I bury the anode into the calcium salt in the bottom of the tube. It only takes a few seconds for the current to drop
by five fold or more. The conductivity is also much higher in the top part of the tube, than in the bottom near the calcium salt. So, there the more
conductive ions appear to have a lower density....
I'm repeating the experiment to make sure I didn't get moisture in the tube.... but a stronger acid (formic) isn't necessarily a better conductor
than a weaker acid in nonaqueous solutions. That was contrary to my expectations.
I should have formic acid in a day or so, so that I'm not restricted to a calcium salt and can repeat the experiment with potassium.
[Edited on 13-5-2021 by semiconductive]
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semiconductive
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Posts: 287
Registered: 12-2-2017
Location: Scappoose Oregon, USA.
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Mood: Explorative
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I have results that are interesting. I'm able to plate silvery iron using formic acid in an ester electrolyte. I'm not sure how stable the solution
is, and will be exploring that.
The electrolyte is separating into three layers. On the top layer is the ester and mostly ethanol (lower density) is present.
In the middle layer, iron oxides (digested by formic acid) floats. They dissolved iron oxide has a distinctive pink/peach color. This is why I'm
able to see the layers easily.
On the bottom layer, the higher density ethyl-carbonate appears to concentrate. It's dissolved in the ester, as well, but tends to sink to the
bottom.
For reasons that I haven't figured out yet ... the ethyl carbonate region has much lower conductivity than the upper two electrolyte layers. I've
repeated the eperiment, and I'm sure theres no water in the electrolyte except whatever tiny amount was made by formic acid dissolving iron oxide.
So, the presence of a small amount of formic acid is able to clean off black FeO from the electrodes and turn it a peach color in solution.
But -- There is no color leaching from the electrodes where they are metallic and shiny into the general solution. I think Iron (II) or Iron (III)
formate is probably a clear substance and not colored. It makes inspecting the plating process easy, and I really like that!
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semiconductive
Hazard to Others
Posts: 287
Registered: 12-2-2017
Location: Scappoose Oregon, USA.
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Mood: Explorative
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It's been over a year, and around 360 different experiments.
Most alcohol baths, seem to be entropy driven during plating. At first, they won't plate, and then for a while they do -- and then after several days
they stop working.
So, of the alcohol baths that do work (and they are rare), it seems to be a competition between being able to carry iron to the destination electrode,
vs. allowing the organic carrier to re-dissolve after plating.
Here's one of the better plating results:
In the photo, I've put in an un-plated 0.7mm graphite hi-polymer mechanical pencil lead, in order to contrast against the one being plated. This is
an ~12mm test tube, and the anode is a standard steel finishing nail.
I've used ammonium thiocyanate as a color indicator in other experiments. It tells me when iron is in the +2 oxidation state vs. +3. This has been a
very useful indicator. Solutions where iron makes it to the +3 state, tend to fail quickly.
I had a theory, that perhaps if a more electropositive metal than iron were used and the voltage raised; that perhaps depositing the other metal first
would allow iron to be reduced from solution.
I've found that column I alkalai salts are pretty useless, and generally deteriorate the alcohol very quickly in to a precipitating goo. But Column
II salts, Mg, Ca, Sr, Ba, do appear to work in situations where they can be made to dissolve in alcohol, or in another solvent that dissolves in
alcohol.
In this photo, I've used a chloride salt, disolved in another alcohol, in order to get it to dissolve in isopropyl alcohol to a small extent.
Otherwise, all of the salt settles to the bottom and has no effect.
There's about 1% water in store bought Isopropyl 99%; and this always precipitates out as a yellow to red sludge.
This plating bath is working fairly well. The graphite to the rightmost, is coated in a silvery grey looking iron deposit. There are places where
the isopropyl sludge has built up too thick to allow plating to continue, but the majority of the electrode is coated in iron and a very thin layer of
yellow organics.
I'd be curious if anyone has suggestions about what I might use to increase the solubility of the precipitated material on the graphite, so as to keep
it clean during plating. I know I could use pulse plating techniques, such as reversing the current direction for a few milleseconds out of a second
to knock it off; but I'd prefer to continue using D.C. sources for now and exploring the chemistry.
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semiconductive
Hazard to Others
Posts: 287
Registered: 12-2-2017
Location: Scappoose Oregon, USA.
Member Is Offline
Mood: Explorative
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| Quote: Originally posted by clearly_not_atara | pKa H2O: 15.7
pKa MeOH: 15.5
Methanol gets you practically nothing as far as stability for electrodeposition. The chemical potential of protons is basically the same.
But the good news is that anhydrous FeCl2 can be obtained from methanol solutions and has good solubility in organic solvents, which is a start.
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I want to say thank you for this advice.
It is generally the halides which are able to electrodeposit iron in all my experiments over the last year.
It is extremely common for iron in the +3 oxidation state to cause the failure of plating. If you hadn't mentioned this, I wouldn't have bought
ammonium thiocyanate as an indicator and learned how sensitive the plating solutions are to the oxidation state of iron.
After taking a photo of the bath with isopropanol, I added NH4SCN, and the color remained yellow. So even though my bath is exposed to air, a very
unlikely chemical seems able to keeping the oxygen out of the bath. This appears to be key in getting a good electroplate. Ferrous ions.
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