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Xenoid
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| Quote: | Originally posted by chloric1
Might sound sloppy but I have 1/4" diameter rods(6.35mm) and I am going to heat with the airgun and mount the rod with a clamp on a ringstand so I can
hold horizontal. |
Chloric, I don't think you'll get it hot enough. It has made a big difference to the MnO2 in going up to 380 oC. Some of these nitrates decompose as
low as 120 oC. Have a look at Table 1. in Patent 4,265,728 the MnO2 lifetime doubles, going from 300 oC. to 400 oC.
Probably 410 oC is the optimum temperature for MnO2 and Co3O4 for that matter, as well.
The hot air from my gun (2300 watts) is only about 300 oC in normal operation. I'd wait for your thermocouple and check the calibration with some
molten lead, too! You need to do each coat for 10 mins., you don't want to be standing around waving a heat gun.... 
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Rosco Bodine
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Shazaam Sargeant Carter , my arms shore are tired from
waving this here heat gun thingie back and forth ....and the handle sure is getting hot , and I'm sweating , and the noise gives me a headache
....would you mind bringing me another glass of lemonade ? 
Xenoids right , you are going to need some sort of fixture
to do this right . Even heating is probably required to keep the coatings from cracking .
[Edited on 7-1-2008 by Rosco Bodine]
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chloric1
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| Quote: | Originally posted by Xenoid
[The hot air from my gun (2300 watts) is only about 300 oC in normal operation. I'd wait for your thermocouple and check the calibration with some
molten lead, too! You need to do each coat for 10 mins., you don't want to be standing around waving a heat gun.... |
@Xenoid- my gun is only 1200 watts and it easily gets 300 C in the LOW setting. It is rated for 530 Celsius at full blast. Of coarse that is 1 inch
from the nozzel. How big is your gun anyways?
@Rosco-Advice noted I will have to jerry-rig something. I did not even think that these coatings could be fragile. And I will calibrate my setup
with my inexpensive stainless steel rod. That thing is almost indestructable!
I used it as a stir
stick for heating molybdenum disulfide to roast to the trioxide!
[Edited on 1/7/2008 by chloric1]
Fellow molecular manipulator
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Xenoid
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@ chloric1 - I just checked my hot air gun it's actually 2000W, it has a mighty air flow, so some of the power is being used there. I made some
measurements about 2 cm from the nozzle with dual thermocouples.
Low setting = 50 oC.
Middle setting = 200 oC. 
Full setting = 360 oC.
Obviously mine is crap! Are you sure your temperatures aren't in Fahrenheit, you are in the US after all....
Edit: I just found the "instruction pamphlet" and it states temperature range 50 oC. to 600 oC. ... hmmm not sure how
they measured the 600 oC. maybe with the concentrator nozzel on to slow air down. Any how it gets nowhere near that in normal operation, firing up the
tube. That's why I had to put a baffle on the end and block up some inlets!
@ Rosco - very funny ...
[Edited on 7-1-2008 by Xenoid]
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Xenoid
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Disaster Strikes Again... !
This really pisses me off... 
The power was off for 2 hours this morning for line maintenance, I was aware of it, so I thought I would switch my chlorate cells off just to be safe.
After 6 days of running "Purple Haze", I had removed a batch of KClO3 and recharged it with KCl, there was already another 1 -2 cm built up on the
bottom a day or two later!
I switched "Purple Haze" off and disconnected the leads from the supply and made sure they were "open circuit" with respect to the cell. The cell was
crystal clear (pink), and the anode looked shiny black, but was emitting a stream of very fine bubbles.
When I returned a couple of hours later, after doing some shopping, the cell was BLACK. The SS cathode was a mess, it was corroded and "moth eaten"
with little pits all over it. It had a coating of black and orange-brown gunk. "Hubert" the anode, still looks black, but I can't believe he hasn't
lost much of his "coat" given the amount of black crap floating around. I filtered the solution, which seems to have a lot of brown colloidal Fe
hydroxide (from the cathode) in it.
I have cleaned everything up (mainly the cathode) and recharged the cell with fresh saturated KCl solution. It seems to be running OK and the
electrical parameters are as before, 3.5 volt - 2.0 amps. It hasn't had time to develop the characteristic pink colour yet.
This is a major set back, the anode was performing extremely well, I was starting to think it would be good for several runs. However if this is what
happens to an anode/cell combination when the power is removed for just 2 hours, I am thinking MnO2 anodes are not viable. I remembered Rosco saying
something about oxide coatings reacting with the electrolyte, and I almost pulled the anode out of the cell, but when I saw how few bubbles were
coming off, I didn't bother...
Can anyone think what reactions were going on here! It's a puzzle because the cell was open circuit. Cell pH during normal operation was 8.1, the pH
of the electrolyte after the disaster was 7.1
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chloric1
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Don't be so mad Xenoid. It is the stainless steel's fault. When I ran with graphite last September, the stainless steel corroded and when the power
went off, the cathode was bit in half by some disgruntled hypochlorite moleculs When I get my thermocouple and a decent 1 1/2 inch diameter aluminum tube I
will give it ago. In my chlorate/perchlorate cells I will be using titanium sheet as the cathode. Hopefully I won't need to hydride this for cathode
use.
By the way my gun is VERY cheap and has two setting Low is 750°F and High 1000°F(398°C/538°) the box list both units becuase we in the US are
Bithermal, some of us understand there are two main temperature measuring units. Eighty percent of the energy is heat, it does not blow very hard.
Push on HUBERT! I know you can do it!
Fellow molecular manipulator
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The_Davster
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I think your anode is just fine. The first chlorate cell I ever ran used a platinum wire anode and a coiled copper cathode. I remember letting it
run for a few hours, and then for whatever reason, I had to leave and turned it off. When I returned several hours later I found the entire copper
spiral had formed blue green stalacites all over, there was just a collumn of insoluble material where the anode was.
I chalked it up to chlorine/HOCl(reduction potential 0.84V) in solution oxidizing the copper, and the base formed in the reduction of hypochlorite
precipitating the copper.
EDIT: Chloric, titanium holds up just fine in a chlorate cell that is off
[Edited on 9-1-2008 by The_Davster]
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Rosco Bodine
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| Quote: | Originally posted by Xenoid
This is a major set back, the anode was performing extremely well, I was starting to think it would be good for several runs. However if this is what
happens to an anode/cell combination when the power is removed for just 2 hours, I am thinking MnO2 anodes are not viable. |
Open circuit and immersed will destroy these anodes .
You should have some sort of standby power , even pull
the assembly and put it in plain water with a battery across it to maintain polarity , if you are not going to rinse and dry it
which is another maybe not best idea , but still better than leaving a cell open circuit .
| Quote: |
I remembered Rosco saying something about oxide coatings reacting with the electrolyte, and I almost pulled the anode out of the cell, but when I saw
how few bubbles were coming off, I didn't bother... |
Doh (sp?)..... Duh ......that's it
| Quote: |
Can anyone think what reactions were going on here! It's a puzzle because the cell was open circuit. Cell pH during normal operation was 8.1, the pH
of the electrolyte after the disaster was 7.1 |
You have an active catalyst for the anode and only the applied potential is shifting the equilibrium in the direction you want it to go . I think the
reactions and potentials were posted before back when you were experimenting with the gouging rod substrate . You may have screwed the pooch
here with having the cell open circuit and wet . I think I have read it only takes about 10 minutes to trash an anode
this way and some coatings are better than others but IIRC it isn't good for any of 'em .
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Xenoid
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| Quote: | Originally posted by Rosco Bodine
Open circuit and immersed will destroy these anodes .
You should have some sort of standby power , even pull
the assembly and put it in plain water with a battery across it to maintain polarity , if you are not going to rinse and dry it
which is another maybe not best idea , but still better than leaving a cell open circuit .
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Actually, rinsing and drying would have been very EASY as the whole electrode assembly is attached to the lid ...
I checked the instantaneous voltage generated by "Purple Haze" at the moment the power is removed, it is around 1.85 volts, but drops rapidly to about
1.5 volts and more slowly after that, I didn't let it get any further. When I turn down the current on my supply it reaches about 10 - 20 mA at about
1.5 volts, so I guess just connecting an alkaline "D" cell across would maintain a trickle current or at least a stable state. Having it switched in
with a simple relay, when power is cut would be easy to organise.
What annoys me most, is now I will never know the true lifetime of "Hubert". I was planning on putting him in a perchlorate cell, or testing at higher
current densities.
Oh well, I guess I'll have to fork out another 10 cents worth of chemicals and an afternoon to fix him up, but I'll run him to total destruction
first!
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hashashan
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Xenoid, I dont want to be mean but kill him fast and take some pics of the new 'Hubert' treatment.
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Rosco Bodine
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Actually this points out a hidden peril for the cell which
ought to be insured against with some sort of standby battery arrangement having a diode in the standby supply lead so that when the main supply is on
it doesn't send
any heavy "charging current" into the standby battery .
What would seem about right would be *two* regular
D cell flashlight batteries with one or more diodes in series . One regular Si diode would drop the 3 volts to about 2.4 volts . Schottky diodes
would have about half
as much drop per diode at 0.3v to 0.4v per diode .
If rechargeable alkaline batteries are used , they could be maintained on trickle charge from the main supply by using
a little three pin controlled current source like an LM334
across the dropping diodes , but oriented in reverse polarity to the diodes , so as to allow a fixed trickle charge
of the standby battery when current is available from
the main cables for the cell . You would know that
whenever your cell is operating that 40 mA for example
or whatever value you have set for the LM334 is a parasitic current being siphoned away from the cell to
the standby battery as your "insurance" premium .
So you would need to account for that parasitic drain
when interpreting your meter readings for the cell
when it is in normal operation .
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Xenoid
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@ hashashan
I'm not sure what you want pictures of. There are images earlier in this thread showing the hot air gun, anodes after baking, the wire hook. I did
take a photo of 'Hubert" being "etched" but the pale purple colour didn't show up very well, so I didn't post it. I gave a pretty full description of
the complete process earlier. It is just, dip the rod in the test-tube of solution, bake in the gun for 10 mins., the rod turns black, repeat several
times.
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The_Davster
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Could someone explain to me how an electrode coating is resistant only with a positive oxidizing charge on it? I find this quite counterintuitive...
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hashashan
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@Xenoid : sorry for asking to be a bit spoonfed, but I would really like a brief but detailed description of the process, I mean what conc. the
solution is , purity etc. .... sorry for the spam
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Xenoid
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@ hashashan
Hmmm... well yes, I think you ARE asking to be spoonfed!
I have given the procedure I used to make "Hubert" on page 11 of this thread, about 3/4 of the way down, posted on 27/12/07. It contains information
on the CONCENTRATION of the solutions used.
The heat gun set up is on page 3, about 2/3 the way down, posted on the 6/12/07.
The solutions were made up from pottery grade chemicals. I made my cobalt nitrate from cobalt sulphate and calcium nitrate (described earlier in this
thread). An easier way is to just dissolve the carbonates in nitric acid, which is what I did for the manganese nitrate. If you can buy high purity
chemicals, by all means use them. Even the concentrations are not critical at this early stage, you will still get coating with ORDER of MAGNITUDE
variations in the concentration. If the concentration is too high you will get excess flakey deposits, but it will still be coated, just rub of the
excess!
The point is there ARE no hard and set rules, I am changing various parameters each time I make a new anode. There is no point in EXACTLY duplicating
what I have done, try something a bit different.There are so many possible parameters to change, that it is overwhelming for one person to do.
I have just finished another anode, but it is still basically the same as "Hubert" because I am impressed with the way he is performing, I will
describe this later.
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tentacles
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I'll pick up some manganese and cobalt myself tommorow, want to ask the pottery shop about a K type thermocouple as well. Given the ease of making a
"hubert", and if he can last through even just 1 run, it would be rather simple to make a bunch of these at a time.
I got some gouging rods through my FIL the other day and they're in my KCL solution making chlorate.
[Edited on 11-1-2008 by tentacles]
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Xenoid
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| Quote: | Originally posted by tentacles
......it would be rather simple to make a bunch of these at a time.
I got some gouging rods through my FIL the other day and they're in my KCL solution making chlorate.
[Edited on 11-1-2008 by tentacles] |
.... precisely! I got a bit carried away with my latest effort, I started after lunch and didn't finish until about 9.00pm ....
But even with my simple set-up I could just as easily have made 3 at the same time. With a better baking apparatus (did I mention toaster ovens) it
would be just as easy to make 10 at a time ....
Have fun cleaning up your KClO3 from all that gouging rod rubbish ...
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tentacles
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xenoid: I have a 1L vacuum flask and 110mm buchner funnel, so it shouldn't be too awful. Maybe I'll get spendy and use a piece of real filter paper
instead of a couple coffee ilters.
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Rosco Bodine
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Early in this thread it was an idea to maybe wet sand the Ti rod substrate with glycerin as a way of abrading the passivating layer of TiO2 , and
possibly getting a film of
Ti "glyceryloxide" as an interface layer which might be easily dopable .
And with it later turning out that Bismuth doping is reportedly a useful thing in any of the coatings layers , including the initial interface with
the Ti substrate .......
and that glycerin turns out also to be an excellent
solvent for Bi(NO3)3 , it seems like it could be possible
to form that Bi doped Ti suboxide interface via a mixed
alcoholate ( Ti-Bi glycerylate ) by wetsanding the Ti rod
substrate with glycerin in which is dissolved Bi(NO3)3 ,
and then baking .
This might also work as tertiary system with Co(NO3)2 .
I just finished rereading this thread , and I think what
was revealed here in experiments continued into the
MMO anode thread , still seems on track , with the single exception having been found that the oxidative cold soak deposition of SnO2 cannot be used
with Co3O4 due to the
reducing effect of the SnCl2 attacking the Co3O4 before
depositing SnO2 can seal it off . The possible usefulness of tin nitrate , stannic and metastannic sols , and ammonium stannate and other precursors
, including alcoholates derived from stannic chloride remains a valid proposition .
[Edited on 5-3-2008 by Rosco Bodine]
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dann2
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Hello,
I wanted to have a bash at making a Manganese Dioxide Anode. I have no Manganese Carbonate. Can I make Manganese Nitrate (Manganese (II) Nitrate,
Manganous Nitrate) using Manganese metal + 70% Nitric acid. According to Wiki I can and H is releases so I won't have to worry about the brown gas.
Will I get the hexahydrate when I evaporate all the liquid away?
Cheers,
Dann2
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mnick12
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manganese nitrate
Hi dann2,
I have never made manganese nitrate from the metal, but I do know of two rather cheap alternatives. The first and cheapest uses only two OTC chemicals
both of which can be cheaply purchased at your local garden store, manganese sulfate and calcium nitrate. All you need to do is make a saturated
solution of manganese sulfate and combine it with a calcium nitrate solution, almost right away the calcium sulfate will precipitate out and you will
then be left with a pink solution of manganese nitrate contaminated with calcium. This method like I said is the cheapest, but it has its downfalls
mainly the purity of the final product.
The second method produces a far cleaner product but is also more expensive. So again make a saturated solution of manganese sulfate and combine with
a solution of baking soda, this will form manganese carbonate and sodium sulfate. The manganese sulfate will precipitate out as a pinkish brown
material, and after washing with water it is then reacted with HNO3 to form a more pure solution of manganese nitrate.
both these methods are easy to do and relativly cheap, so I hope this helps.
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dann2
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Hello Mnick12,
I will try that if I don't succeed with the metal. I happen to have some of the metal (ebay grade!) and that is why I am trying the metal first.
Manganese Carbonate is available from the ceramics store too.
I broke off some Manganese metal from the lump I have with a hammer. It is brittle.
I got a mixture of pieces, some very small, some the size of a pea. Added Nitric acid and got brown gas and fizzing. There was supposed to be no brown
gas, only H2, according to Wiki. The small pieces seem to react very quickly. I vacated the room and came back some time later. Lots of white
crystals and still some metal left. Added some more Nitric and left the room. Will see how things are tomorrow.
I want to try a Manganese Dioxide Anode in a pH controlled Chlorate cell to see if it's lifetime is increased. If it's similar to Graphite it's
lifetime should increase by 100 fold.
Cheers,
Dann2
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Rosco Bodine
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I read in an old reference that MnO2 will dissolve in HNO3 if you add a bit of sugar to it.
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dann2
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Hello,
From Mellor Chapter LXIV Manganese page 441
Volume XII
______________________________________
§ 25. The Manganese Nitrates
C. W. Scheele 1 first prepared manganous nitrate, Mn(NOs)2' It is obtained in
Roln. by dissolving manganous carbonate in nitric acid. According to J. F. John,
Inanganese dioxide (q.v.) dissolves in nitric acid in the presence of reducing. agents,
which form some nitrous acid, or, ~:t,ccording to C. W. Scheele, by exposing the
system to sunlight, which decomposel3 some. nitric' acid into nitrous acid and oxygen.
J. F. John obtained a soln. of the nitrate ,by dissolving the metal in hot nitric acid.
J. W. Gatehouse obtained manganous nitra~ by heating to 165° to 200° a .mixture
of manganese dioxide and ammonium nitrate. The evaporation of the aq. soln.
furnishes a syrupy liquid which yieldB crystals of the hexahydrate. V. M. Peshkova
described the preparation of the salt. .A.. Guyard noted the occurrence of
manganous nitrate in native Chili saltpetre; and H. St. C. Deville and H. Debray
__________________________________________
Metal + Nitric seems OK
Dann2
[Edited on 11-3-2010 by dann2]
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dann2
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Hello,
Can anyone tell me what is the color of Manganese Nitrate crystals.
From here
http://www.chemyq.com/En/xz/xz1/1227popjv.htm
it says they are colourless or rose red (huh)
Mine are colourless (white).
Dann2
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