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jpsmith123
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Hello Dann2,
I speculated that certain types of MMO anodes may make perchlorate. (I don't know exactly which types, but taking everything I've read at face value,
I would say PtO2 and PdO based MMO coatings stand a good chance).
This is based on Beer's patent# 3711385 (attached; see examples 8 and 11, and read the first few pages of text), and also on statements from at least
two people who claim to have made it using a pool chlorinator anode.
IIRC, in the body of the patent, Beer claims that the PGM oxides have catalytic properties similar to, if not generally better than, the metals
themselves.
The implication is that if Pt makes perchlorate, then so too will a thin film of PtO2; and it will supposedly last much longer. Having the other
oxides present, e.g., TiO2, makes the coating more robust, but also changes the catalytic properties, according to what I read.
And that's all I can say about it at this point.
What bothers me is: Why is nobody selling a commercial MMO based perchlorate anode? And why only PbO2 and Platinum? Why not MnO2 and SnO2 based anodes
for that matter? For all the various patents out there, only Pt and PbO2 are commercially viable for some reason?
Attachment: 3711385.pdf (1.1MB)
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dann2
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Hello,
MnO2 anodes were used years ago (can't remember where I read this) and were called Duriron. Perhaps a search of the Patents for Duriron would pull up
some info.
Since they seem to have faded away perhaps they were not so good at doing their job.
Dann2
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alancj
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| Quote: | Originally posted by jpsmith123
What bothers me is: Why is nobody selling a commercial MMO based perchlorate anode? And why only PbO2 and Platinum? Why not MnO2 and SnO2 based anodes
for that matter? For all the various patents out there, only Pt and PbO2 are commercially viable for some reason? |
I'm guessing that the amount of capital required and just trying to get companies to switch to an unproven anode may play a big part in the limited
commercial success of a new type of anode. Even if other types technically work the marketing guys might not be able to persuade the penny pinchers.
-Alan
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Rosco Bodine
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| Quote: | Originally posted by dann2
Hello,
MnO2 anodes were used years ago (can't remember where I read this) and were called Duriron. Perhaps a search of the Patents for Duriron would pull up
some info.
Since they seem to have faded away perhaps they were not so good at doing their job.
Dann2 |
Something doesn't make sense there .....maybe the duriron was used as a substrate ?
Duriron is the trade name for a durable iron corrosion resistant high silicon content ~15% iron alloy used for
plumbing tanks and valves in the chemical industry .
It was invented in 1912 and the Duriron company of Dayton Ohio became a public corporation 1942 , growing into a
large conglomerate known today as flowserve
http://www.flowserve.com/eim/index.html
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MadHatter
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Gouging Rods
Dann2, I performed the tests on my gouging rod perchlorates using the
sulphuric acid on sugar/KClO4 tests and with methylene blue. Both tests confirm
that I have KClO4. All the sulphuric acid did was char some of the sugar and the
methylene blue turned a very pretty violet colour. The KClO4 works GREAT in flash mixes.
I will acknowledge that the efficiency with additives such as potassium dichromate,
potassium persulphate, or sodium fluoride helps but I'm tired of eating up gouging
rods and the efficiency is still horribly low. Since perchlorates will be harder to obtain
because of the wankers at the CPSC, it's time to move on finding a more durable
anode. PbO2 on a graphite substrate works but the coating, even thick, is fragile.
I'm running out of KClO4 so I need that anode soon, especially with the July 4th
holiday around the corner.
BTW, I've visited and must say you have a great website ! 
From opening of NCIS New Orleans - It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !
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dann2
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Hello Madhatter,
I went back to the original 'Perchlorate from Graphite post'(not the actural name of post) and snipped out the full process description.
The url is:
http://www.sciencemadness.org/talk/viewthread.php?tid=5050&a...
Most of snips come from page 2
_________________________________________
..............
JP, the treatment for gouging rods involves peeling off the copper plating and then soaking
in linseed oil. This slows the erosion in the cell. I made 8 LBS of KClO4 using gouging rods.
It's a matter of technique. Keep the cell temperature below 40 C and the erosion proceeds
at a much slower rate. Use a cut up steel can for the cathode and don't worry about
the iron hydroxide that forms because the fluffy white shit is so insoluble that it, along with the
carbon bits filter out readily. I bend the steel to make an inverted V shape and the gouging
rod sits directly below it. This way, the rising chlorine runs into the hydroxide formed at the
cathode. My cell has a 5 litre volume.
Few posts later:
My cell body is basically a 5 litre glass cookie jar that I found at Walmart. I like the V-shape
cathode because the chlorine or oxygen rises from the anode to mix with cathode
products. This is why I don't need to stir. The worst possible configuration for the
electrodes is to have them sitting on opposite sides of the cell. Very little mixing occurs.
As mentioned before, keeping the cell temperature below 40C(104F) keeps the rate of
erosion down.
Solubilities for compounds from CRC 62nd Edition(1981-1982), grams per 100ml H2O:
KClO4 .75 @ 0C 21.8 @ 100C
NaClO4.H2O 209.0 @ 15C 284.0 @ 50C
I start my electolyte at 9% by weight KCl. A little NaCl is mixed in because oxidation
of NaCl is more efficient than KCl. The metathesis reaction with KCl forces KClO4 out of
solution because of its much lower solubility. I put 2g of NaF in the electolyte to improve
current efficiency. Voltage is at 6 and amps are adjusted to keep the cell temperature
below 40C. After completion, FeSO4 is used to destroy any residual chlorate. The rest is
fractional crystallization to get the KClO4.
Few posts later:
Perchlorate production begins when the chloride(by weight) drops below 10%. This is why I
start my electrolyte at 9% to get things going immediately. I have to replace the gouging rods
a few times during the process but that's fine with me because they're cheap to use.
8 LBS of KClO4 for about 3.12 USD(6 rods) is bargain IMHO. I still have almost 90 rods left.
A few were consumed early on while tweaking the technique and of course producing
straight chlorate using saturated KCl solutions. The lovely cactus needle like formations
are indications that the chlorate is being produced.
Dichromates, fluorides, and persulphates are used to increase the efficiency of the operation.
I've used all 3 at different times. Personally, I like NaF. It works very well and it's cheap.
As for cathodic protection, I couldn't give a damn. I'm not worried about consuming a
soup can.
Few posts down:
I like to have .2 amps per square centimeter on the anode. That's about 7 amps on a 3/8"
by 12" gouging rod. I keep the voltage at 6.
_________________________________
END OF PROCESS CLIPS
The reading of the process is not clear to me how or what you started with.
I don't know if some of the inconsistencies are typos.
You say
" A little NaCl is mixed in because oxidation
of NaCl is more efficient than KCl."
But we are making Perchlorate, do you mean a little NaCl03?
You say:
"I like to have .2 amps per square centimeter on the anode. That's about 7 amps on a 3/8"
by 12" gouging rod."
Surface area of 11 inch(active length) by 3/8 inch rod = 83.6cm squared. At 7 amps that's 0.083 amps per square cm on the anode.
Which is the correct (approx.) figure?
To dissolve 3180 grams K. Chlorate (enough to make 3600 grams Perc.) at 35C takes about 25 liters. Is this approx. what you used or did you keep
adding Chlorate into the one 5 liter cell (one big run)?
To dissolve 3600 grams (8 lbs) KClO4 (K. Perchlorate) it takes about 18 liters of water at 95C. Is this approx. what you used in total when
recrystallizing?
You will need far more IMHO to stop K. Perc. from crystallizing out on the filter to get rid of the black shit.
I would like to ask the following:
What was the starting concentration of 'stuff'(list all salts + approx. concentrations) in the cell?
Did you use the same 5 liters of water/electrolyte solution through out the manufacture of the 8 lbs of K. Perchlorate?
How long (approx.) did it take to make the 8 lbs of K. Perchlorate?
How many amps into cell?
What was the current density on the Gouging rod anode?
Did you use one Gouging rod at a time?
I tried making Perchlorate (Sodium Chlorate + about 2% Sodium Chloride + NaF) using Graphite and got no sensible amounts of Perchlorate forming after
a huge run time.
Is the difference all to do with using K. instead of Na..........I have me doughts but then again it is something I have not done using (more dilute
compared with Na) mostly K salts.
Sorry about all the questions. More will probably follow!!!!!!!!!!!
If Perchlorate can be made at a rate of 6/8 = 0.75 (3/8" by 12")rods per lb Perchlorate I will eat my (and yours too) hat.
| Quote: |
I'm running out of KClO4 so I need that anode soon, especially with the July 4th
holiday around the corner.
BTW, I've visited and must say you have a great website !
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Thanks.
If I can get this to work I will put it on the front page! Most of the material comes from others hard work.
Fourth comming up?? Time to get out the Gouging rods.
Cheers,
Dann2
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dann2
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| Quote: | Originally posted by Rosco Bodine
Something doesn't make sense there .....maybe the duriron was used as a substrate ?
Duriron is the trade name for a durable iron corrosion resistant high silicon content ~15% iron alloy used for
plumbing tanks and valves in the chemical industry .
It was invented in 1912 and the Duriron company of Dayton Ohio became a public corporation 1942 , growing into a
large conglomerate known today as flowserve
http://www.flowserve.com/eim/index.html |
Hello Rosco,
The place where I saw Manganese Dioxide anodes being called Duriron was in the following artical:
JOURNAL OF APPLIED ELECTROCHEMISTRY 8 (1978) 327-332
The preparation and behaviour of magnetite anodes
M. HAYES*, A. T. KUHN
Department of Chemistry and Applied Chemistry, University of Salford, Salford, Lanes., UK
......, as do the 'duriron'
or MnO2-coated electrodes......
It is available on this web site.
Perhaps I have taken it out of context.
Good luck with your other endeavors.
Dann2
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Rosco Bodine
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Yeah I think you have it out of context . Because duriron is a trademark brand name nearly a hundred years old for the corrosion resistant
silicon-iron alloy , which has been used alone for anodes or substrates . Maybe it was used as the center core in those cast magnetite anodes
or maybe even by itself in some applications .
Thanks , I got a couple of weeks work to catch up
at another location so I may be going offline for a
few days at a time .
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12AX7
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Hmm. Applying this to my cell, I find around 6V, 100A is required (about a horsepower!), and I'll be able to produce roughly um...
Well, one 3/8" x 12" rod is 7 in^3, and if it averages 0.75 of them to make a pound, then it goes at a rate of 5.3 in^3 graphite/lb KClO4 produced
(note this includes the unusable stub left over at the top). (You can figure the typical density of industrial graphite into this to get wt/wt.)
I have two 40 in^3 graphite bars, therefore I could produce 15.2 pounds of potassium perchlorate.
But no estimate of time, current efficiency, temperature control (that size cell WILL need cooling with half a kilowatt of heat inside it) or
voltage/current control (you mention 6V, but you also say current was controlled -- how, exactly, was it controlled while voltage remains fixed?
(Length of rod in solution?) Or did you just forget your electronics when you said that?), etc.
Incidentially, the two bars cost me about $20. If the cell runs for one week, producing 15 pounds of perchlorate, it consumes 117.6 kWh (assuming a
conservative 700W consumption figure; yeah, I would use schottky rectifiers for the power supply), costing $12 of electricity and $20 in graphite.
Plus a few hours of my time, though counting that is tricky (as I'm not on payroll when I'm at home, and if I were doing this industrially, I would
have much larger cells -- and, ironic to this thread, no graphite muck -- providing economy of scale). So I'd get around $2/lb KClO4. Seems kind of
expensive, at least compared to a licensed drum of it...
Tim
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Rosco Bodine
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A manganese analogue of duriron
There is a manganese loaded cobalt - silicon alloy which was developed as an improvement for duriron when used for the
anode in copper refining . See attached patent . I do not know if the alloy is presently manufactured or what would be its trade name . Likewise I
think there also is a high manganese content variety of duriron itself .
It would seem to be a very likely candidate substrate for a baked on beta MnO2 material dervied from Mn(NO3)2 ,
which could probably then be coated with PbO2 .
I have seen a few other references to high manganese or high chromium content varieties of stainless steel alloys which have been baked and treated
with manganese and/or chromium salts , and other salts also , in schemes which are analogous to those used for titanium substrate anodes .
BTW ordinary 316 stainless has been mentioned in a few patents as something of a possible substitute for titanium which has performance in service
almost as long as a titanium substrate anode , the main difference being that after a year or so of operation when the protective oxides layer fails
and the substrate alloy is exposed , that the stainless substrate disintegrates .....while the the titanium substrate just flakes off its coatings and
then usually remains for the most part in one piece , except for pitting in the places where the coatings have failed . So while operating normally
with intact protective coatings , evidently
a few alloy or alternative substrates to titanium are possible , but the titanium substrates fail more gradually and slowly when the protective
coatings eventually crack or are are otherwise permeated by the electrolyte . Evidently none of these anode combinations are absolutely permanent
or perfect , it is simply a matter of some combinations being longer lasting than others and having different behaviors when they do fail sooner or
later .
Attachment: US1437507 Cobalt Manganese Chromium Silicon Alloy for Anode.pdf (293kB)
This file has been downloaded 662 times
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Rosco Bodine
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more concerning possible "activated" graphite
Reportedly a *single* dip and bake treatment with certain oxides which are catalytic can also increase the erosion life of anodes by 10 times compared
with an untreated anode , and this applies to graphite anodes . This treatment may even be more effective on the cheaper grade more porous grades of
graphite .
I would suppose that multiple coats and an increased buildup of the thickness of the catalytic oxide would have an even greater effect .
Cobalt nitrate is specificially reported in this regard in the attached patent . Bismuth is also a known catalytic oxide ,
and manganese would probably work as well . This is a similar sort of process as would be used to apply the baked on intermediate oxide layer on a
titanium substrate . And evidently it is significant benefit to a carbon anode also .
The carbons will still erode , as this superficial treatment
does not result in a permanent anode . But it may be a relatively simple way of slowing the erosion and improving the efficiency of the anode
significantly .
[Edited on 24-6-2007 by Rosco Bodine]
Attachment: US6001225 Baked Cobalt Oxide coated_anodes.pdf (43kB)
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Xenoid
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MnO2 impregnated/coated carbon gouging rods!
| Quote: | Originally posted by Rosco Bodine
I would suppose that multiple coats and an increased buildup of the thickness of the catalytic oxide would have an even greater effect .
Cobalt nitrate is specificially reported in this regard in the attached patent . Bismuth is also a known catalytic oxide ,
and manganese would probably work as well . This is a similar sort of process as would be used to apply the baked on intermediate oxide layer on a
titanium substrate . And evidently it is significant benefit to a carbon anode also .
The carbons will still erode , as this superficial treatment
does not result in a permanent anode . But it may be a relatively simple way of slowing the erosion and improving the efficiency of the anode
significantly .
[Edited on 24-6-2007 by Rosco Bodine] |
Hi
I am currently having a go at something like this - trying to impregnate and coat carbon gouging rods with MnO2 to extend their life particularly in a
chlorate cell!
Thermal decomposition of Mn(NO3)2 to MnO2 seems to be a particularly suitable technique for the amateur to explore for a number of reasons.
1) Manganese precursor chemicals are readily available from hydroponics and pottery suppliers.
2) It doesn't involve the use of poisonous Pb chemicals.
3) There are no "complex" procedures involved ie. plating.
4) There is "heaps" of literature and patents available - this technique is used for the production of tantalum capacitors and others since the 60's
and for various anodes.
Not currently having nitric acid I made Mn(NO3)2 solution via the double dissolution (metathesis) reaction of Ca(NO3)2 and MnSO4 causing the
precipitation of CaSO4. The resulting white curdy gloop was so thick that more water needed to be added to make it pourable. This was then placed in
my homemade pressure filter and a slightly pink clear solution was obtained. I am currently just using this solution as obtained, without any further
purification, or adjustment of concentration as a "proof of concept"
My gouging rod treatment consists/wil consist of:
1) Stripping the copper in the usual electrochemical procedure (I always leave about 2 or 3cm of copper plate on the non-pointed end so a wire can be
soldered on, or a stainless steel clip attached, to achieve good electrical contact.
2) Soaking the rods in 2 changes of distilled water overnight.
3) Drying in a oven at 150oC for several hours.
4) 10 (yes 10!) cycles consisting of;
a) vacuum impregnation for 30mins in the Mn(NO3)2 solution. (I just use an old rotary refridgeration compressor and PVC pipe with endcaps - the same
as for the linseed oil impregnation, I have no idea of the vacuum achieved - its not much!).
b) warm air drying to remove surface moisture.
c) 15 mins heating at 100oC
d) 15 mins heating at 200oC (for the heating cycles I am currently using a hot air gun attached to an aluminium tube in which the rods sit. I have a
cheap DVM with a thermocouple attached to measure the temperature)
e) cooling to room temperature
Note: Poisonous NO2 is emitted during the heating (thermal decomposition) cycle. The smell starts to become noticeable at about 140oC
After each thermal cycle the rods appear to be covered in small nodules of MnO2 where solution has erupted out of the numerous holes and cavities that
these rods are renowned for. I merely wipe them with a tissue to smooth off the surface before proceeding to the next cycle.
So far I have completed 8 of the 10 cycles.
I can see the MnO2 coat building up on the surface, around the holes and cracks but there is still solution being ejected from various points so the
pore space of the rods is not yet completely filled with MnO2. I would like the the pore space filled to stop "wicking" of the electrolyte.
5) I then intend to do 10 further cycles of just dipping and heating in an attempt to build up the suface layer of MnO2.
6) Followed by a final "burn" for about 30 mins at 250oC to complete the process.
I am currently only doing 2 rods for experimental purposes but it would be just as easy to do do a dozen rods at the same time!
I realise this all sounds quite complicated, but there is no "easy" route to a homemade anode! This procedure has LOTS of scope for amateur
experimentalism! Including:
1) Purity of initial chemicals.
2) Concentration of solution.
3) Water/Ethanol solution - Mn(NO3)2 is apparently soluble in ethanol.
4) Duration, number, and temperature of impregnation/ decomposition cycles.
5) Introduction of "doping" elements as mentioned in previous posts.
6) Additional plating of MnO2 or others over the thermally decomposed MnO2
7) Thermal decomposition onto high quality graphite and valve metals in etched or sintered form (why are they called valve metals???).
I will report how I get on in several days time!
Xenoid
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Rosco Bodine
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Added MnCO3 should help increase the loading
The residue of sulfates could cause you troubles going from
the double decomposition using calcium nitrate . It would probably be cleaner to use sodium carbonate or bicarbonate
and filter out the carbonate , rinse it good with distilled water , then neutralize the residue with HNO3 , or possibly boil it with ammonium nitrate
.
Added 10% content of MnCO3 to the Mn(NO3)2 will increase the viscosity and loading and quality of the baked film of
MnO2 . So you could save out some of the carbonate or
you could carefully weigh the carbonate and then add only enough HNO3 for 90% conversion . I suspect what this does is result in a solution
containing either a basic nitrate of manganese or a soluble double salt , or both as a sort of sol complex which thickens the mixture . The mixture
may not be stable on keeping so you may have to prepare it as needed .
Cobalt , Bismuth , and Antimony are reportedly dopants for MnO2 that are known to be catalytic for perchlorate production .
Just a guess , but others of interest might be be vanadium ,
chromium , cadmium , tin , iron , lead , phosphorous and boron .
I would bet money that graphite manufacturers probably have some sort of proprietary recipe of dopants which were added as deliberately included
impurities to the carbon powder which was / is made into graphite destined for particular customers .....things which improved its performance in
certain niche applications . Even the spectrum of light produced by arc lamps was probably modified by certain additives and also carbons used for
anodes probably each had a special recipe .
So what is being done here is probably a rediscovery of
something that was being done already a hundred years ago . A lot of this technology was probably never published ,
and that is why it is impossible to find , it is locked away in some company's safe as a process secret . Or perhaps it is simply hidden in plain
sight in some long list of unspecified use but specified formulations of various graphites for industry .
About the "valve metals" ....it goes back to " Fleming valves "
which were rectifier tubes , and the British reference to rectifiers which allow one direction current flow as " valves "
for their similarity to check valves like used in water lines or other hydraulics . When a valve metal is used as an anode
there is formed an oxidized layer of the metal which gradually
becomes more and more resistant to current flow as that layer grows in thickness . It usually has the property of a
diode .....so that if the polarity is reversed and the valve metal substrate is made the cathode , then current flows
much more easily , while on the other hand it essentially stops current flow in the direction that formed the oxide layer . The idea of dopants is
to disrupt that polarizing effect towards electrical current flow , so that the metal which ordinarily would stop functioning as an anode continues to
conduct electricity as easily as possible in the same direction as the current which would otherwise anodize
it , and then stop . The idea is to keep the corrosion resistance of the oxide layer mostly intact , but at the same time to allow easy flow of
current through the oxide to the metal anode .
[Edited on 24-6-2007 by Rosco Bodine]
Attachment: US3553087 Improved beta MnO2 from Mn(NO3)2 plus MnCO3.pdf (159kB)
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Xenoid
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| Quote: | Originally posted by Rosco Bodine
The residue of sulfates could cause you troubles going from
the double decomposition using calcium nitrate . It would probably be cleaner to use sodium carbonate or bicarbonate
and filter out the carbonate , rinse it good with distilled water , then neutralize the residue with HNO3 , or possibly boil it with ammonium nitrate
.
Added 10% content of MnCO3 to the Mn(NO3)2 will increase the viscosity and loading and quality of the baked film of
MnO2 . So you could save out some of the carbonate or
you could carefully weigh the carbonate and then add only enough HNO3 for 90% conversion . I suspect what this does is result in a solution
containing either a basic nitrate of manganese or a soluble double salt , or both as a sort of sol complex which thickens the mixture . The mixture
may not be stable on keeping so you may have to prepare it as needed .
[Edited on 24-6-2007 by Rosco Bodine] |
Hi,
Yes, I was aware of the sulphate interference, it was mentioned in one of the papers I looked at. But, not having any nitric acid I thought I'd give
it a go anyway, this is just a preliminary attempt at treating gouging rods. If this method shows any promise I'll try and crystallise out some pure
Mn(NO3)2 - not sure how easy this will be with its high solubility - does anyone have a solubility curve for Mn(NO3)2?
Hmmm.. adding MnCO3, it has a solubility of .0065 ie. insoluble not sure how - it may be in the paper you quoted, I havn't read it yet!
As I pointed out previously, there is plenty to try out here - starting with the purity of the main ingredient 
I have now completed 10 cycles, the rods look like they have been in a fire, and are covered in a nodular coating of MnO2.
Xenoid
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dann2
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Hello Xenoid,
At the end of the day someone has to do it!
| Quote: | Originally posted by Xenoid
4) There is "heaps" of literature and patents available
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OH NO!!!!!!!!!
| Quote: |
Not currently having nitric acid I made Mn(NO3)2 solution via the double dissolution (metathesis) reaction of Ca(NO3)2 and MnSO4 causing the
precipitation of CaSO4.
Xenoid |
Surely you will get no Sulphate interference as it is easy to seperate the chemicals as one is insoluble?
Dann2
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Rosco Bodine
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| Quote: | Originally posted by dann2
| Quote: | Originally posted by Xenoid
4) There is "heaps" of literature and patents available
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OH NO!!!!!!!!! |
If you are digging potatoes and just happen to find a gold nugget ....you don't throw it away just because it isn't a potato !
Old Rosco is like a snapping turtle when he latches onto something , he doesn't let go till it thunders 
| Quote: | | Quote: |
Not currently having nitric acid I made Mn(NO3)2 solution via the double dissolution (metathesis) reaction of Ca(NO3)2 and MnSO4 causing the
precipitation of CaSO4.
Xenoid |
Surely you will get no Sulphate interference as it is easy to seperate the chemicals as one is insoluble?
Dann2 |
It's a rough separation usually because the CaSO4 is not entirely insoluble and it takes some subsequent purification to get out the sulfate that
sneaks over on the first pass . It probably won't matter much on something like this , but the sulfate impurity can be an issue in some reactions , so
it's generally better to go a different way like the carbonate intermediate .
BTW , concerning bismuth oxide , here is a link for a possibly useful method for a nanoparticulate crystalline bismuth oxide which develops at 400C .
http://dx.doi.org/10.1016/j.ceramint.2004.06.013
[Edited on 25-6-2007 by Rosco Bodine]
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Xenoid
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MnO2 treatment of gouging rods - continued!
I have now done 4 cycles of surface treatment on the rods!
The cycle comprises;
1) Dipping the rod in the Mn(NO3)2 solution for about 5 seconds. I've added a few drops of Monsanto "Pulse" to the 100mls of dipping solution (Pulse
is a penetrant/wetting agent for use with "Roundup" herbicide).
2) Warm air drying, to remove visible moisture.
3) Heating for 15 minutes at 200oC
I am starting to think that the vacuum impregnation cycles were not nescessary because if the surface coat is robust enough, the internal parts of the
rods will not be penetrated by electrolyte anyway! Solution erupting from the tiny cracks and holes during the heating phases of the vacuum
impregnation has left a somewhat rough surface which may not coat smoothly!
I am now doing a third rod with just surface treatment for comparison.
Incidently, the concentration of my Mn(NO3)2 solution as obtained from the metathesis reaction and filtering procedure ended up being about 119.2g in
500mls. That's assuming perfect purity and stoichiometry, so lets say about 226g/litre assuming 95% efficiency. Thats about 1.26 Molar.
Xenoid
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Rosco Bodine
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nice work
Here is some solution data for Mn(NO3)2 pulled from CRC
and a manufacturer label for a 50% solution .
Mn(NO3)2 - 4 H2O m.wt. 251.01 m.p. 25.8C b.p. 129.4C
colorless to pink crystals sol. 100 ml H2O @ 0C 426.4 g.
calculated saturated solution @ 0C
contains 57.76% Mn(NO3)2
(anhydrous basis m.wt. 178.95 )
commercial supplied 50% Mn(NO3)2 in H2O
density @ 25C 1.54
From this data it can be seen that a constant boiling solution
will likely form at 129.4C , or at any rate that temperature
being reached by a boiling solution will contain molten
Mn(NO3)2 tetrahydrate boiling in its own water of crystallization , the solution at 129.4C contains
71.29% Mn(NO3)2 by weight .
For each 100 g. of the 129.4C constant boiling solution ,
an addition of 42.6 ml of distilled H2O will dilute that
71.29% solution to a commercial concentration 50% solution .
I do not have a solubility curve to check this against , but
probably half that amount of dilution water would give much
closer to a saturated solution at room temperature ,
( 58.8%) with little or no crystallization unless it was
cooled to nearly freezing .
My conclusion is that ~15ml dilution water per 100 g. of the
129.4C constant boiling solution would probably be about right , to give a concentrated working solution good for use around room temperature , and
that would be a 62% solution of Mn(NO3)2 .
On the temperature , I think you are going to need a bit hotter than 200C ....more like 300-325C range , I have seen stated range from 300C for 5
minutes to 350C for 10 minutes .
BTW ,
There is a possible value for a combined "bimetal spinel"
sort of compound between bismuth and manganese oxides which might form from thermal decomposition of their mixed nitrates or other mixed salts . All
I have found so far is that there is a range of mixed oxides of varying proportions that are possible and they are conductive and catalytic , but
require a higher temperature for their formation something around 400C . Most of what I have found on this relates to cathodes and supported catalysts
, pigments ....but nothing so far turns up in the search concerning anodes .
[Edited on 25-6-2007 by Rosco Bodine]
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dann2
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Hello,
2c worth...
I guess this process is only useful for Gouging rods as 'better' graphite will not be porous.
Dann2
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Xenoid
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Hi Dann2
No, better quality graphite would be superior, it is still very porous, and the smooth surface would be good for the Dip 'n Bake technique. I'm only
using gouging rods because I can currently buy them for about 35 cents each, and also leaving a little Cu plate on the end allows a near perfect
electrical connection by soldering or metal clip!
BTW great website, many thanks!
Regards, Xenoid
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Xenoid
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MnO2 impregnated/coated anodes completed - phew...!
I have now completed 12 dip and bake cycles on the two impregnated anodes;
9 cycles of dip, air dry, heat for 15 mins. at 200oC
3 cycles of dip, air dry, heat for 15 mins. at 280oC
I have increased the temperature in accordance with Rosco's recommendations above! I had come across papers using temperatures ranging from 150 -
270oC, I did not realise temperatures above 300oC were used! The temperature control on my hot air gun baking system is not all that accurate anyway,
and probably varies by 20 - 40oC from one end to the other!
The rods now have a hard lumpy coating, there is no MnO2 smudge on the fingers when they are run along the rod!
The rods have gained in weight by about 2g, they were about 38g when I started and are now 40g, thats as accurate as I can be as I only have kitchen
type scales.
I tried to measure the change in diameter using a micrometer, but the lumpy nature of the coating makes this difficult, it may be as much as .1mm so
the coating thickness would be no more than about 50 microns.
Now I have to tidy up my "lab" and carry out some tests!
Xenoid
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Rosco Bodine
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excerpted notes concerning perchlorate production
A couple of things that might be nice finishing touches .
Brush on a final coat having a dopant catalytic for perchlorate
like bismuth nitrate or antimony chloride , or mix one of these
with some of your manganese nitrate and do a final bake .
Also add a soluble phosphate 3 g. / liter to your chloride bath that will be converted to perchlorate .
Justification as follows below ....
From US4072586:
column 5 line 29 :
The anodes of the present invention are also particularly suited for the electrolytic production of perchlorates. A preferred anode for the
electrolytic production of perchlorate comprises an electrode with an outer layer of catalytic .beta.-MnO.sub.2 containing from 0.5 to 5.0% by weight
of at least one metal selected from the group including As, Sb and Bi.
.beta.-MnO.sub.2 anodes have been tested for the production of perchlorate by electrolysis of an aqueous electrolyte having the following composition;
150 g/l of NaClO.sub.3
450 g/l of NaClO.sub.4
3 g/l of Phosphates and at 40.degree. C and at a current density of 1200 to 1700 A/m.sup.2, and remarkable faraday efficiencies ranging from 70 to 92%
were recorded. The best results, namely faraday efficiencies above 90%, have been obtained with .beta.-MnO.sub.2 coatings containing up to 5% by
weight of As, Sb and Bi.
The doping agents such as As, Sb and Bi are thought to shift the oxygen potential of the catalytic .beta.-MnO.sub.2 coating above the perchlorate
formation potential. This means that the energy gap between the main anodic reaction
ClO3 + H2 ----> ClO4 + 2H + 2e
and the side reaction
H2O ----> 1/2(O2) + 2H + 2e
is increased, therefore increasing the perchlorate faraday efficiency.
[Edited on 26-6-2007 by Rosco Bodine]
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Xenoid
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Sorry Rosco, I don't currently have any Bi, Sb or As salts.
I have just finished making up a 660 g/L solution of NaClO3 it is made with NaClO3 that has been recrystallised 3 times, so should be very low in
chloride, I have checked it with methylene blue and it is also free of perchlorate.
I'm planning to run the anode at a current density of 150 mA/cm2 that's about the middle of what you quote above!
Xenoid
[Edited on 26-6-2007 by Xenoid]
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Rosco Bodine
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It should work anyway , just take a bit longer .
How about the phosphate or some phosphoric acid and soda ? TSP powdered detergent would probably work okay .
About the chloride .....I'd try to go to perchlorate
starting from NaCl . A big point about many MnO2 anode patents was the electrolysis of brine so it should hold up okay .
That current sounds about right . They run up to even double that current density on PbO2 . So long as the cell is staying below 60C , keep cranking
it up and cross your fingers . 40C is a pretty safe level and 60C would be
about redline .
[Edited on 26-6-2007 by Rosco Bodine]
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Xenoid
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Yeah, I have some potassium phosphate, and I think I can get some Sb and Bi chemicals but at the moment I just want to see if the anode holds
together!
We can try adding all the fancy chemicals at a later stage.
I'll use the 2nd anode on some NaCl solution assuming the first one holds together, and makes perchlorate. 
Xenoid
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